FORESTRY PAMPHLETS PROTECTION ~ VOL. IX Disease *> The Chestnut Bark Disease, By N. J. Giddinge. Bui. 137, W. V. Univ,,Agri. Exp. Sta. The Chestnut Bark Disease. Bui. 178, Conn. Agri. Bxp. Sta. Report of the Connecticut Agricultural Experi- ment Station, being Part X of the Biennial Report of 1909-1910. /Report of the Connecticut Agricultural Experi- ment Station, being Part V of the Annual Report of 1912. The Leaf Blotch of Horse-Cnestnut. By Y. B. Stewart. Cornell University Agri. Exp. Sta. Forest Pathology in Forest Regulation. By E>>. P. Meinecke, Bui. 275, U. S. Dept. of Agri. Endothia Parasitica and Related Species. By C. L. Shear, Neil E. Stevens and Ruby J. Tiller. Bui. 380, U. S. Dept. of Agri. Parasitic Rhizoctonias in America. Bpl, 189, Illinois Agri. Exp. Sta. Parasitic Rhizootonias in America. By Geo. L. Peltier, Bui. 189, Univ. of Illinois Agri. Sxp. Sta. I. The Red Rot of Conifers. By F. H. Abbott. Bui. r 191, Vermont Agri. Exp. Sta. •Mistletoe Injury to Conifers in the Northwest. By James R. Weir. Bui. 360, U. S. Dept. of Agri. A Preliminary Report on the Occurrence of Westdrn Red-Rot in Pinus Ponderosa. Bui. 490, U. S. Dept. of Agri. New Facts Concerning the White-Pine Blister Rust. * By Perley Spaulding. Bui. 116, U. S. Dept. of Agri. £he White-Pine Blister Rust. Farmers1 Bulletin 742. By Perley Spaulding. 'Crown Gall. Bui. 118, Univ. of Ariz* Agri. Exp. / Sta. Investigations of the Rotting of Slash in Arkan- sas. By W. H. Long. Bui. 496, U. S. Dept. of Agri. •n>oderina Deformans, an Undescribed Needle Fun- •# gus of Western Yellow Pine. By James R. Weir. 1 Discovery of Internal Telia Pro^io^ "by a Species PROTECTION -- VOL. IX (COflT'D) of Cronartium* By Reginald H. Colley. Peridermium Harknessii and Cronartium Quercuum. By E. P. Meinecke. Bulletin 137 March, 1912 JVgrtmltural MORGANTOWN, W. VA. DEPARTMENT OF PLANT PATHOLOGY The Chestnut Bark Disease N. J. GIDDINGS The Bulletins and Reports of this Station will be mailed free to any citi- zen of West Virginia upon written application. Address Director of Agricultural Experiment Station, Morgantown, W. Va. The State of West Virginia Educational Institutions THE STATE BOARD OF CONTROL. Charleston, West Virginia. James S. Lakin, President Charleston, W. Va. John A. Sheppard, Charleston, W. Va. E. B. StephensOn, Treasurer, - - . - Charleston, W. Va. The State Board of Control has the direction of the financial and business affairs of the state educational institutions. • THE STATE BOARD OF REGENTS. Charleston, West Virginia. M. P. Shawkey, State Superintendent of Schools, President, George S. Laidley, - G. A. Northcott, Earl W. Ogelbay, - J. B. Finley, Charleston, W. Va. Charleston, W. Va. Huntington, W. Va. Wheeling, W. Va. Parkersburg, W. Va. The State Board of Regents has charge of all matters of a purely scholastic nature concerning the state educational institutions. West Virginia University Thomas Edward Hodges, LL.D., President AGRICULTURAL, EXPERIMENT STATION STAFF. E. Dwight Sanderson, B.S. Agr., Bert H. Kite, M.S., W. E. Rumsey, B.S. Agr., N. J. Giddings, M.S., - Horace Atwood, M.S. Agr., W. H. Alderman, B.S. Agr., I. S. Cook, Jr., B.S. Agr., L. M. Peairs, B.S. Agr., M.S., C. A. Lueder, D.V.M., A. L. Dacy, B.Sc., Frank B. Kunst, A. B. - Charles E. Weakley, Jr., J. H. Berghius-Krak, Kristian Hv. Knudsen, Dipl. ing. Hubert Hill, B.S., M.S., David C. Neal, B.S., E. C. Auchter, B.S. Agr., - L. H. Sutton, B.S., B.S. Agr., W. J. White, .... M. A. Stewart, Uriah Barnes, LL.B., Director - Vice-Director and Chemist Entomologist - Plant Pathologist Poultryman - Horticulturist Agronomist - Entomologist Veterinarian Associate Horticulturist Assistant Chemist - Assistant Chemist Assistant Chemist - Assistant Chemist Assistant Chemist Assistant Plant Pathologist - Assistant Horticulturist Assistant Horticulturist Bookkeeper Librarian - Secretary BULLETIN 137. THE CHESTNUT BARK DISEASE A DANGEROUS ENEMY OF WEST VIRGINIA'S CHESTNUT TREES. The blight or bark disease of chestnut seems to be, in many respects, the worst pest that has appeared, in the forests of this country. It is unusual for a disease to destroy the entire growth of a plant in any section, but this blight has been found to attack practically every chestnut tree in its line of advance, leaving in its wake only dead and dying trees of that species. We should be thankful indeed that it has not been found to attack other species of our forest trees since that would ser- iously complicate matters. The chestnut timber is of very great value and importance in this state and it would seem well for us to take any reason- able and necessary steps for the prevention or control of the disease in West Virginia. The average annual cut during the past few years is about 118 million feet, and this figure does not include poles, cross ties, or posts. The value of the nuts is also great, as food for man, or for fattening hogs. Shipments from one railroad station last fall aggregated 155,092 pounds. We have secured estimates from several lumbermen as to the present standing chestnut timber of the state. These esti- mates range from more than one billion feet to ten billion feet. Taking five billion feet as a reasonable average, and $3.00 per In publishing this bulletin on the Chestnut Bark Disease we have drawn freely from all available publications on the subject. We are especially indebted to Dr. Haven Metcalf of the U. S. Department of Agriculture, Mr. A. B. Brooks, former State Forester of West Virginia, and Mr. S. B. Detweiler of the Pennsyl- vania Chestnut Blight Commission. 364026 210 W. V. AGR. EXPERIMENT STATION [Bulletin 137 thousand as stumpage value, we have a total valuation of $15,- 000,000. These figures do not mean a great deal as there are many things to be considered aside from the simple lumber value of the chestnut. Our West Virginia forests deserve far more attention than, they have thus far received, and it is hoped that the publica- tion of this Bulletin will help to bring about some definite action both in regard to the Chestnut Bark Disease and gen- eral forestry work in this State. FIG. 1. — A fine old tree, but dying from the bark disease. HISTORY. Attention was first called to this disease by Dr. H. W. Merkle, of the New York Botanical Gardens. During the summer of 1904-5 he noticed -that a few of the chestnut trees in the parks appeared to be dying in a peculiar manner, and ,he brought the matter to the attention of Dr. W. A. Murrill, the Mycologist. In a paper on the subject given in the 1905 March, 1912.] THE CHESTNUT BARK DISEASE. 211 report of the Zoological Society Merkel says, "It has spread to such an extent that today it is no exaggeration to say that 98 per cent of all the chestnut trees in the parks of this bor- ough are infected. The spread of this disease is so sudden that unless some radical measures are taken or a natural ettemy of this fungus deve1ops, it is safe to predict that not a live specimen of the American chestnut (Castanea dentata} will be found two years hence in the neighborhood of the ZOO- PIG. 2. — A beautiful grove a few years ago, but all chestnut dead now. logical Park''. Valiant efforts were made to save trees which were not yet diseased by spraying them thoroughly with Bor- deaux mixture, while many which were only slightly diseased were pruned and repruned, but all of their endeavors availed nothing, and today those great parks are destitute of the chestnut trees. During the years 1905-6 Dr. Murrill studied the disease in laboratory, greenhouse and park. As a result of his studies he found it to be new and undescribed, tho a fungus similar 212 W. V. AGR. EXPERIMENT STATION [Bulletin 137 to the one which causes this disease is known to occur in Europe. He published a careful description of the disease and its behavoir in 1906. His work was followed by a great deal of discussion as to the cause and importance of the disease, and meanwhile the chestnut trees were dying by thousands and tens of thousands. The Office of Forest Pathology at Washington, D. C., has devoted considerable time to the study of this disease, especial- ly as to its manner of spreading, distribution, and methods of control. Pennsylvania was the first state to give the matter serious consideration and more will be said of their work under an- other heading. DESCRIPTION. The disease may attack a tree of any age, and any part of the tree. It is caused by a fungus, and this seems able to start its growth only in wounds of some sort, but when we consider the squirrels, insects, and birds which may make small wounds through the bark it is easy to see that there are numerous points of entrance. It finds conditions most favorable for its growth just be- tween the bark and the wood. Once started, it spreads rapidly and soon girdles the part upon which it is growing. It is this characteristic of girdling which makes it especially destruc- tive. Only a small amount of tissue is actually invaded by the fungus, but the entire tree, limb, or twig is killed beyond that point. When a twig or limb is diseased, the spores or fruit- ing bodies of the fungus are washed down toward the trunk, which soon becomes infected and girdled. The disease is most noticeable during late spring and sum- mer. During this period, the recently killed or dying limbs are easily detected from some distance, on account of their dis- colored foliage. The leaves on a diseased branch turn to a reddish brown color, and finally wither, but they have a ten- March, 1912.] THE CHESTNUT BARK DISEASE 213 FIG. 3. — A diseased tree in young chestnut orchard. to branches. Note dead leaves clinging FIG. 4. — An old tree making its final efforts to live. Girdling at a lower point will soon complete its death. 214 W. V. AGR. EXPERIMENT STATION [Bulletin 137 dency to remain on the tree for some time. The burs on in- fected branches usually remain on the tree during the winter following its girdling. Diseased trees very frequently produce sprouts or "suck- ers" in considerable numbers. These may appear on the trunk or near the base of the tree. Such sprouts soon become infected, however, and very few survive more than two or three years. FIG. 5. — Young tree showing postules on smooth bark, and sprouts. (See also Fig. 11, page 221.) A closer examination reveals the diseased band near the base of the affected portion. It is especially conspicuous on smooth bark, causing a reddish brown discoloration and pro- ducing numerous little pustules which break through the bark and set free vast numbers of spores. These spore masses are orange colored but vary considerably in appearance accord- ing to climatic conditions. During warm, moist weather they are especially prominent and sometimes may be seen as long, curly, yellow threads issuing from the pustule (figure 6). March, 1912.] THE CHESTNUT BARK DISEASE. FIG 6. — A very close view of a diseased portion. Note the summer spores issuing in long twisted strings from some of the pustules. 216 W. V. AGR. EXPERIMENT STATION [Bulletin 137 Such threads are composed of countless numbers of spores held together by some sticky material. Rains dissolve this adhesive material and carry the spores to lower portions of the same tree or to others standing close by. When a branch is girdled by cutting around it, there is api to be an enlargement produced just above the wound, and a similar effect is often noted in limbs attacked by this disease. In fact many of the gross symptoms are exactly similar to those which would be produced bv^ mechanical or insect girdl- ing. If older portions are attacked, the discoloration and pus- tule formation are not so evident, as most of the pustules are produced in the fissures of the bark. Such bark, when cut through, is found to be discolored and breaks up easily like punk. Tapping upon this bark will usually produce a pecu- liar dull sound. The fungus may continue to grow in the dead bark for some time. It was not generally thought to be capable of growth in the wood, but three investigators, Dr. Caroline Rumbold, W. H. Rankin, and J. Franklin Collins, in different sections of the country have reported finding it upon the wood during the past season. (i) Besides the common so called summer spores mentioned above, the fungus produces another kind known as the per- fect or winter spores. These are darker in color and the pus- tules are less conspicuous. They are most frequently produc- ed during the late fall, and help the fungus to survive any unfavorable weather conditions. DISTRIBUTION. As previously stated, this disease threatens the destruc- iton of all chestnut timber in the Eastern States. At the present time it is known to be present in Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Pennsyl- (1) This statement is taken from unpublished data furnished by the parties mentioned. Rankin gives a detailed description of the fungus growth on wood and reports finding fruiting pustules on wood entirely stripped of its bark and exposed to weathering. March, 1912.] THE CHESTNUT BARK DISEASE. 21' pIG. 7. — A view to show how bark is rotting and cracking. FIG. 8. — A more advanced stage than fig. 7. Bark peeling off. 218 W. V. AGR. EXPERIMENT STATION [Bulletin 137 vania, Delaware, Maryland, Virginia, West Virginia, and the District of Columbia. A glance at the map, figure 10, will show how general has been the spread from New York City as a center. In consid- ering this map one should remember that a diseased tree is practically doomed to die. There are numerous diseased areas, especially in Pennsylvania, which have been found since this map was plotted. FIG. 9. — A view showing complete destruction on young chestnut stand in forest area. E. R. Hodson, of the U. S. Forest Service, writing of this disease in 1908, says, "In Pennsylvania it is no where abun- dant yet, although it exists at Easton, South Bethlehem, and Morrisville, and is repprted as far north as Pocono Mountains, and as far south now as Philadelphia." In recent correspon- dence with the Pennsylvania Commission for the investiga- tion and control of this disease, they have sent us a map show- ing that the area of general infection now includes nearly one-half of the state. A similar rapid spread has been record- ed in other states and a great united effort should be made to prevent its further progress. March, 1912.] THE* CHESTNUT BARK DISEASE. 219 FX PL A /VA Tl ON : i All frees c/eod A //Trees diseased L oca/ diseased areas Former diseased areas FIG. 10. — Map showing distribution of diseased chestnut. The area of gen- eral infection in Pennsylvania is much greater than would be indicated by this map. 220 W. V. AGR. EXPERIMENT STATION [Bulletin 137 Dr. Spaulding; of the U. S. Department of Agriculture, has made careful notes on this disease in the Connecticut Val- ley during the past three years. In summing up his obser- vations there he states, "There can be no shadow of doubt that in the three years, 1909 to 1911, inclusive, the disease has spread so seriously as to now be beyond hopes of control in the lower Connecticut Valley." (i) In the case of New Jersey infection is already so general that there is very little hope of savfng any chestnut in that state. Europe is fearful of the disease and Italy has already taken steps to prevent its introduction there. PREVENTIVE MEASURES. Numerous experiments have been conducted in the hope of finding some practical method of controlling the chestnut bark disease and some good results have been secured. Those most actively engaged in work along this line at present are the Pennsylvania Chestnut Tree Blight Commission and the Office of Forest Pathology in the U. S. Department of Agri- culture. Spraying appears to be of little value, and, of course, is entirely impractical in forest areas. The method which has finally been adopted aims to prevent the further spread of the disease from the area of general infection and to destroy all diseased trees outside this area. To accomplish the first point, it is essential to establish a line beyond which it will be extremely difficult for the disease to progress. The main, advancing front of the diseased section must come to a point where there are no more chestnut trees within easy range of infection. Large unwooded areas and forest tracts free from chestnut should form as large a part of this boundary line as (1) From unpublished data furnished by Dr. Spaulding. March, 1912.] THE CHESTNUT BARK DISEASE. 221 FIG. 11. — Note sprout production around base of this diseased tree. 222 W. V. AGR. EXPERIMENT STATION [Bulletin 137 practicable. In other portions it may be necessary to cut all chestnut trees both healthy and diseased, in a belt some miles wide along the line. The disease is left largely to itself in the area enclosed by this line while careful search is made for all diseased trees outside that area and they are destroyed when found. All chestnut timber in the generally diseased area should be cut and utilized as rapidly as possible but the disease will find itself checked upon reaching a boundry de- stitute of chestnut, — 'the same as a forest fire when it comes to a broad river. In the case of individual trees which are quite valuable it is often possible to prolong their lives or even to save them by careful tree surgery. Diseased twigs and small limbs should be removed. The larger limbs and trunk may be treated by carefully cutting away all diseased bark and into the healthy bark around the edges. A layer of wood should also be removed from beneath this bark and the entire wound painted over with coal tar. The tools used for removing bark and wood should be very sharp, so as to make clean, smooth cuts, and the work must be done with great care and thor- oughness, if good results are to be expected. LEGISLATION. The control of this disease is a matter which requires prompt action on the part of every state where it has been found. These states are all awakening to a realization of the danger from the Chestnut Bark Disease and Pennsylvania, Virginia, and New York have already taken steps to prevent its further spread. Pennsylvania was the first state to make a definite move along this line. Her legislature passed a bill carrying appropriations of $275,000. for use in investigating and controlling this specific disease. The full title of that act is as follows : "An act to provide efficient and practical means for the prevention, control and eradication of a disease affecting the chestnut trees, commonly called the chestnut tree blight; March, 1912.] THE CHESTNUT BARK DISEASE. 223 FIG. 12. — Map showing where the disease has been found in West Virginia. The specimen from Whetsell was picked up by a tourist and the one from Lewis- burg by a summer visitor. The disease at Pickens was looked up by Mr. A. B. Brooks and the infected tree, which came from a nursery, was destroyed. 224 W. V. AGR. EXPERIMENT STATION [Bulletin 137 providing for the destruction of trees so affected ; creating a commission to carry out the purpose of this act; fixing penal- ties for the violation of the provisions hereof ; and making an appropriation therefor". Soon after the passage of the bill, in June 1911, a com- mission was appointed. At present they have a well organiz- ed staff and are preparing for a tremendous campaign against the disease this coming season. They have accomplished much work of value already, and have had a considerable number of trained men in the field all the time. Space will not permit a detailed discussion of their methods, but they would surely serve as a safe model for any other state. RECOMMENDATIONS. / Since the disease is known to be present in West Virginia, we owe it to ourselves and to neighboring states to take defi- nite and immediate steps for preventing its further spread. The disease has been found in a number of chestnut nur- series and in several cases local areas of infection have been directly traced to such diseased stock. Any one contemplat- ing the purchase of chestnut trees from nurseries would do well to correspond with the Agricultural Experiment Station at Morgantown, before securing them. Any such trees should be inspected by competent authorities in this state before being accepted or paid for. Some careful inspection work should be done in the vicini- ties of the three local infections already reported for this state and in the northern and north eastern portions of the state during the next season. The control of this disease is a matter of great economic importance to the State of West Virginia, and deserves the serious consideration and hearty co-operation of every citizen. We would urge that everyone make it a point to take care- ful note of the condition of any chestnut trees which may March, 1912.] THE CHESTNUT BARK DISEASE. 225 come under their observation, especially during the season of 1912. Specimens may be compared with the pictures and descriptions given in this bulletin. In case there is the least suspicion that a tree is diseased, samples of bark and wood from the girdled portion should be sent to this Station. We would also be pleased to have correspondence from any one who has made observations wThich might be of gener- al interest or value, concerning the chestnut or other forest trees of this State. CONNECTICUT AGRICULTURAL EXPERIMENT STATION NEW HAVEN, CONN. BULLETIN 178, SEPTEMBER, 1913. THE CHESTNUT~BARK DISEASE CONTENTS. page Cause of Disease 6 Description of Disease 6 Remedies Tried 7 Dissemination of Spores 8 Progress of Disease 9 Distribution in Connecticut 9 Distribution in the United States n R ation to Host Conditions 12 Present Situation and Future Prospects in Connecticut 12 Work Done in Connecticut 13 Work Done by Other States 14 Historical 15 Range and Conditions of Growth 15 Character of Wood and Utilization 16 Mill Practice 17 Recommendations » 18 The Bulletins of this Station are mailed free to citizens of Con- necticut who apply for them, and to others as far as the editions permit. CONNECTICUT AGRICULTURAL EXPERIMENT STATION. BOARD OF CONTROL. His Excellency, SIMEON E. BALDWIN, ex officio, President. PROF. H. W. CONN, Vice President Middletown GEORGE A. HOPSON, Secretary Wallingford E. H. JENKINS, Director and Treasure^ New Haven JOSEPH W. ALSOP Avon WILSON H. LEE Orange FRANK H. STADTMUELLER Elmwood JAMES H. WEBB Hamden ADMINISTRATION. CHEMISTRY. ANALYTICAL STATION STAFF. E. H. JENKINS, PH.D., Director and Treasurer. Miss V. E. COLE, Librarian and Stenographer. Miss L. M. BRAUTLECHT, Bookkeeper and Stenographer WILLIAM VEITCH, hi Chargt of Buildings and Grounds. LABORATORY. JOHN PHILLIPS STREET, M.S., Chemist in Charge. E. MONROE BAILEY, PH.D., C. B. MORISON, B.S., C. E. SHEPARD, G. L. DAVIS, Assistants. HUGO LANGE, Laboratory Helper. V. L. CHURCHILL, Sampling Agent. Miss E. B. WHITTLESEY, Stenographer. PROTEIO RESEARCH. T. B. OSBORNE, PH.D., Chemist in Charge. Miss E. L. FERRY, M.S., Assistant. BOTANY. G. P. CLINTON, S.D., Botanist. E. M. STODDARD, B.S., Assistant. Miss M. H. JAGGER, Seed Analyst. Miss E. B. WHITTLESEY, Herbarium Assistant. ENTOMOLOGY. W. E. BRITTON, PH.D., Entomologist ; State Entomologist. B. H. WALDEN, B.AGR., First Assistant, Q. S. LOWRY, B.S., I. W. DAVIS, B.S., Assistants. Miss F. M. VALENTINE, Stenographer. FORESTRY. WTALTER O. FILLEY, Forester ; also State Forester and State Forest Fire Warden. A. E. Moss, M.F., Assistant Station Forester. Miss E. L. AVERY, Stenographer. PLANT BREEDING. H. K. HAYES, M.S., Plant Breeder. C. D. HUBBELL, Assistant. GENERAL DESTRUCTION OF CHESTNUT BY BLIGHT. THE CHESTNUT BARK DISEASE. Endothia gyrosa var. parasitica (MuRR.) CLINT. By E. M. STODDARD, Asst. Botanist, and A. E. Moss, Asst. Forester. To the owner of chestnut woodland the vital questions are; What is killing the chestnuts? and, What are the prospects of maintaining the chestnut as a forest tree? FIG. I. TREES KILLED BY CHESTNUT BLIGHT. It is the purpose of this bulletin to answer the first question and to give such other information that the reader may have a clearer understanding of the problem and judge for himself what 6 CONNECTICUT EXPERIMENT STATION, BULLETIN NO. 178. is the best course to pursue under the particular conditions in which his woodlot is situated. CAUSE OF DISEASE. First of all, let it be clearly understood that the chestnut blight is caused by a fungus and not by an insect, as is often erroneously supposed. The fact that insects of various kinds are found in the dead bark of an affected tree has often led to the conclusion that the trouble is of insect origin, but such is not the case and insects have no part in causing cffestnut blight. DESCRIPTION. The chestnut disease is caused by the fungus technically known as Endothia gyrosa var. parasitica. This fungous parasite pene- FIG. II. BLIGHT STARTED THROUGH INSECT INJURY (A), AND PRUNED BRANCH (B); C. MATURE FRUITING PUSTULES ON SMOOTH BARK. CHESTNUT BARK DISEASE. 7 trates the bark to the wood of the chestnut tree, killing the invaded tissues, but does not enter into the wood to any appre- ciable extent nor does it affect directly any part of the tree other than that with which it comes in contact. The tree or branch is killed only when the disease goes completely around it, thus girdling it and stopping the flow of sap to the parts above the infected area. The mycelium or vegetative part of the fungous plant grows, as has been stated before, in and beneath the bark and the spores are borne in characteristic red-brown or orange-colored pus- tules. These are seen dotting the surface of the cankers on smooth bark and thickly clustered in the crevices of rough bark. The spores are the bodies by which the organism perpetuates itself and are borne on the fruiting pustules in countless num- bers. There are two forms of these spores, one of which is borne in the summer and the other in late fall and winter, both being capable of infecting chestnut trees under the proper con- dition. So small are the summer spores that 8,000 of them placed end to end equal an inch in length. The chestnut blight fungus does not so far as known injure any other kind of tree nor does it usually attack a tree unless the bark has been injured or the tree is in a weakened condition. It has, however, been found to a very limited extent on a few oaks, but never doing any appre- ciable injury. - REMEDIES TRIED. At present there are no sure remedies known for this dis- ease, because the fungus grows- wholly within the tree, only its fruiting pustules appearing on the surface, thus making it very difficult to control the disease by spraying even if it were practicable to do spraying in a chestnut forest. Other methods of control have also proved unsuccessful. Spraying. It has been claimed that spraying with Bordeaux mixture will prevent trees from becoming infected, which it doubtless would if the tree had no wounds in the bark and could be covered completely with the mixture at all seasons of the year. But this is nearly impossible and surely impracti- 8 CONNECTICUT EXPERIMENT STATION, BULLETIN NO. 178. cable except perhaps on single trees used for ornamental pur- poses. Medication. Injecting various substances into the tree has been tried but with no success, as any substance sufficiently poisonous to kill the blight is injurious to the tree, and further- more it is difficult to make a tree absorb any very great amount of material injected into it. Cutting Infected Trees. The removing of all infected trees has been tried but as with the other remedies its success has been only indifferent at the best, as it is hard to find all infected trees when scouting for the disease, and the few not found are sources of new infections. The expense and trouble of destroy- ing infected portions of the tree after cutting makes this method of control out of the question for treating chestnut woodland. Thus at present we are without any effective method of com- bating this trouble in the forest and at best are only partly successful with single specimens in a yard or park. DISSEMINATION OF SPORES. There are several ways in which the blight may be. spread, but from our own observations it would seem that the wind and possibly birds, especially those which hunt for larvae of insects in the bark, are chiefly responsible. It can be readily seen that when an affected tree is producing countless millions of such minute spores the wind will easily blow them to a considerable distance. This is especially true of the winter spores, which are forcibly ejected from the sacs in which they are borne. These spores lodging in a wound in the bark of a chestnut tree or being washed there by the rain would start a new infection of the disease. As the summer spores are produced in sticky masses, birds may pick them up on their beaks and feet and thus carry them to new localities. Other ways of dissemination are insects and transportation of diseased chestnut wood from one place to another. The fungus often produces spores for one or two years on cut wood especially when the bark has been left, so that diseased wood can be a source of infection for CHESTNUT BARK DISEASE. 9 some little time. Rains are very effective in washing spores to various parts of the tree below the infected portion. PROGRESS OF DISEASE. While we have not much definite data at hand to show just how fast the disease progresses after attacking a large tree, we have found by inoculating small seedlings and sprouts that these may be entirely girdled in one season, and from general observations on marked trees at Stamford and Middlebury it takes at least two years to kill the tree and probably three or four. Of course how long it takes the blight to kill a tree FIG. III. SPROUT WITH DEAD BARK AROUND INOCULATION POINT. depends on where the tree is attacked. If it is attacked on the small branches these will be killed but the rest of the tree will remain healthy and in a growing condition for a considerable time. On the other hand if the infection is on the main trunk this will be girdled and the entire tree killed in a much shorter time. Certain weather conditions also apparently affect the rate of development of the fungus. DISTRIBUTION IN CONNECTICUT. At the present time the chestnut blight is distributed entirely over Connecticut. The accompanying maps show its spread from 1908 to 1912 and also show approximately the varying degrees of damage done in various parts of the state. The trouble is more serious in the southwestern part of the state and west of the Connecticut River. This is probably due to the fact that there is more chestnut in the western half. It was reported DISEASE NOT REPORTED DISEASE NOT BAD DISEASE BAD FIG. IV. KNOWN DISTRIBUTION OF CHESTNUT BLIGHT IN 1908. DISEASE NOT BAD DISEASE BAD DISEASE VERY BAI FIG, V. KNOWN DISTRIBUTION OF CHESTNUT BLIGHT IN IQI2. DISTRIBUTION OF CHESTNUT BLIGHT IN CONNECTICUT. CHESTNUT BARK DISEASE. I I first in the southwestern towns of the state but recent studies of the disease prove that it was present to a greater or less degree in scattered localities throughout the state as early as in these reported towns. DISTRIBUTION IN THE UNITED STATES. Chestnut blight is present in Massachusetts along and west of the Connecticut River, in Rhode Island it is scattered and seri- FIG. VI. A-B. CANKERS ON SMOOTH (A) AND ROUGH (B) BARKED TREES. ous in certain localities, and it has also been reported from Ver- mont and New Hampshire. In New York it is progressing north along the Hudson River and is present in western Long Island. In New Jersey the chestnut has suffered over the entire state and in Pennsylvania the trouble is serious in the eastern and bad in the southeastern part. The disease occurs gen- erally in Delaware, while Maryland, Virginia and West Virginia have it scatteringly, the points of infection being few and incon- spicuous in the latter state. Thus we see that the disease is 12 CONNECTICUT EXPERIMENT STATION, BULLETIN NO. 178. spread in varying degrees of seriousness over nearly the entire northern territory where chestnut grows. RELATION TO HOST CONDITIONS. From our own observation and from the opinions of wood- land owners who have watched the spread of the disease it would seem that the dry seasons, which are unfavorable for the growth of the chestnut, have been an important factor in the spread of the disease. It has been fountl that chestnut growing on dry hill-tops is generally more seriously affected with the blight than that in lower land where there is more moisture. Chest- nut growing on dry hillsides has been evidently killed entirely by dry conditions, as no blight could be found on it. Chestnut injured by fire or in other ways is invariably more quickly attacked by this disease and often it is the trunks of these trees which are infected, thus causing the death of the tree much quicker than if the twigs and small branches were attacked. Instead of the chestnut bark disease being an introduced dis- ease as is thought by some, it seems more probable that it was present in this country, growing inconspicuously on dead and dying trees, and that after the chestnut was weakened by a succession of dry seasons it became an active parasite and attacked and killed living trees. PRESENT SITUATION AND FUTURE PROSPECTS IN CONNECTICUT. The present situation in Connecticut is that the disease is still spreading and unless its progress is checked by some natural causes the future prospects are not bright for chestnut in this state. However, instances have been noted where trees were overcoming the disease and blight cankers which had attained a diameter of eighteen inches were healing over, this healing process having been begun in 1911. This condition is not gen- eral, but if it is possible for some trees which have had favorable growing conditions to overcome the disease we may expect that if the seasons are such that the trees are able to make a more vigorous growth the disease will decrease in virulence consider- ably. Of course, predictions as to the final outcome are at best rather uncertain and evidence at hand furnishes arguments for CHESTNUT BARK DISEASE. 13 both the optimist and the pessimist, but until the chestnut is nearer extinction than at present, a prediction of ultimate destruc- tion does not seem warranted. WORK DONE IN CONNECTICUT. The work done on the chestnut blight in Connecticut by the Experiment Station consists of a survey of the state to determine the extent and seriousness of the disease, and of a thorough inspection of a tract on the state forest in Portland for the pur- pose of locating and cutting out diseased trees and also a plot where affected trees were located, counted but not cut out. Besides this a large amount of laboratory work has been done to determine various points of scientific interest in regard to the life history and cultural characteristics of the blight fungus. The survey of the state was made by members of the Botanical and Forestry Departments visiting and locating the disease in all towns from which specimens had not already been received. In this survey no attempt was made to locate definitely all the points of infection in every town, but each town was inspected in a very general way to locate the disease and get an approxi- mate idea of the amount of chestnut. The work in the Portland forest consists of a thorough inspec- tion of a definite tract in which all infected trees are located, cut out, the brush burned and the infected timber removed and peeled. Such as is not large enough for timber is burned for charcoal nearby. As a check on the results obtained on this tract an adjacent tract is inspected, the trees counted and not cut out, thus showing whether the cutting out has any control on the disease. This has been done for two years and, while the results have so far been negative, this experiment must be carried on for a series of years to arrive at definite conclusions. Besides this inspection a small amount of work has been done in the way of peeling or burning the infected stumps to determine the effect of such treatment on the sprouting of the stumps and on the destruction of the disease. At this writing it is too early to say what the results of this experiment will be. Judging from the time taken to do a small amount of such work it would prove too expensive for the owner of timber land to undertake cutting diseased trees and burning the stumps. 14 CONNECTICUT EXPERIMENT STATION, BULLETIN NO. 178. WORK DONE BY OTHER STATES. The work of studying and combating chestnut blight has been taken up by the various states in various ways and on a larger or smaller scale according to the views of the investigators and FIG. Vn. SMALL BRANCHES ON OPEN GROWN TREE KILLED BY BLIGHT. to the amounts of money appropriated for the work. Massachu- setts has done some work in locating the diseased areas, but noth- ing in the way of control measures, the same course being fol- lowed by Rhode Island. Pennsylvania has expended $275,000 on the study and work of combating the blight. Spraying, cut- ting out infected trees, medication and tree surgery were tried, CHESTNUT BARK DISEASE. 15 and while many experiments of interest have been performed no very definite progress, in our opinion, has been made in discover- ing successful and practical measures of control. Maryland, Virginia and West Virginia are expending small sums on locating points of infection with an idea of possibly removing the scattered areas of infection at a later date if the success of such treatment shall seem to warrant it. The chest- nut in New Jersey and Delaware has been so nearly destroyed that little work of any kind has been undertaken. HISTORICAL CONSIDERATION. The chestnut blight was first noticed in the New York Zoologi- cal Park by H. W. Merkel in the summer of 1904. In 1905 it was so serious that measures were taken to control it, and the first description of the trouble was published in the report of the New York Zoological Society for that year. From a botani- cal standpoint the first work was done by W. A. Murrill of the New York Botanical Garden in 1906. Shortly after MurrnTs work the study of the blight was taken up by Clinton of this Station and by Metcalf and Collins of the United States Depart- ment of Agriculture. Since then many investigators have become interested in the study of this disease and the opinions and dis- coveries have been nearly as numerous as the investigators. RANGE AND CONDITIONS OF GROWTH. Chestnut ranges from southern New Hampshire south to Georgia and Alabama. Connecticut is near the northern limit of its range, which accounts for the decrease in per cent, of this species toward the northern part of the state and on the cool northern slopes. It occurs nearly pure on medium to deep well-drained sites, but on the drier ridges and in the swamps it is crowded out of the stand by species better adapted to the conditions. This tree requires direct light and forms a wide spreading tree in the open, while in the forest the demand for light causes increased height growth, forming a clear full-boled tree. Chest- nut sprouts very abundantly, even when the tree cut is 100 years or more in age. The nuts are largely eaten, but a few are scattered by the birds and animals which accounts for the numerous seedling trees to be seen in abandoned fields. The l6 CONNECTICUT EXPERIMENT STATION, BULLETIN NO. 178. sprout tree grows much more rapidly in youth but the seed tree will often overtake and pass it in forty-five or fifty years. Chestnut forms the larger part of the stand in the southern counties of the state but decreases in the northern portion, where white pine is more abundant. East of the Connecticut River it does not form as large a percentage of the stand as in the FIG. VIII. PURE STAND OF CHESTNUT. western part of the state. It usually occurs in pure stands or mixed with oak, tulip, and other hardwoods. CHARACTER OF WOOD AND UTILIZATION. Its wood is durable in contact with the soil and has been largely used in the form of posts, ties, and other products which are exposed to the weather.' The stands in the northern portion of the state have been coaled a number of times to furnish char- coal for the iron mines which have been in operation there since colonial days. The wood is soft and easy to cut, and when dry burns with a steady heat leaving little ash, which fact has resulted in the use of this species to the almost total exclusion CHESTNUT BARK DISEASE. 17 of the hard woods in the brass industry. The brickyards and the lime kilns also use it when it can be obtained. These numerous uses for the smaller products, such as cordwood, have resulted in large areas of sprout forests under 30 years of age, in which the percentage of chestnut has been on the increase, due to the great vigor with which the stumps sprout. In those sections of the state where the market for cordwood is not as good, the stands are usually left until pole or tie size. Here the percentage of seedling trees is slightly greater, due to the increased seed production of the more mature trees. These stands, as a whole, are mixed with a greater variety of species and are in a better condition to withstand the spread of the chestnut blight, as there are in many cases enough trees of other species to continue the stand even if the chestnut is entirely removed. There are very few stands in the state in which the trees are of a size to make lumber. This is largely due to the ready market for ties and poles, but it is also due to the fact that in a sprout stand the trees begin to deteriorate after it reaches the age of fifty to sixty years. Native chestnut is the wood most used in this section for ties and poles. Chestnut and red cedar are most commonly used for posts. Chestnut is used for timbers in the construction of a large number of buildings, especially on the farm where the owner has his own wood lot. When the tree is large enough to saw, the planks are commonly used in the wooden bridges to be found throughout the state. The boards are used as rough siding and to a limited extent in the manufacture of boxes, but this use is limited by the weight of the lumber. As an interior finish, this wood is coming into favor, but up to the present time the southern lumber is preferred because of better milling and closer grading. Chestnut is used in furniture as the core for veneering. MILL PRACTICE. The chestnut of this state is milled by small portable outfits which have a daily capacity of five to fifteen thousand feet per day. The timber holdings are small and a mill has to make frequent moves which tends to make the owner careless in setting up, with the result that there is a tendency to produce lumber of varying thickness. The mills have circular, inserted 1 8 CONNECTICUT EXPERIMENT STATION, BULLETIN NO. 178. tooth saws which cut out a 9-32 inch kerf, which means a loss of one board in four. This is probably unavoidable as the stands of timber are so small that any other form of mill is out of the question, but the unnecessary loss due to the saw not lining up or the teeth not, being in good shape is avoidable. Where the stand is being cut for ties the felling crews cut the logs into tie lengths, and the sawyer does not save the boards that the cut may contain above the tie contents, as there is little demand for eight-foot boards. If the logs were cut in two tie lengths, this question of tfae short board would be avoided and a merchantable product obtained in place of a thick slab. The sale of a stand by the thousand feet is undesirable since there is then a tendency on the part of the operator to cut as rapidly as possible, and not to get the maximum amount out of each log. There is a lack of appreciation of the loss from the cutting of high stumps and leaving merchantable material in the tops. If the stump is six inches too high, the loss in the average tree is from one to two per cent, and it is the best timber in the tree which is wasted. RECOMMENDATIONS. Cutting a stand of chestnut simply because there are a few diseased trees scattered through it is to be avoided if possible. The stand should be watched and when the loss from the disease is greater than the increase by growth the stand should be cut. The value of the timber is steadily increasing so long as it is growing thriftily, and it is good policy to hold a stand as long as possible, to get the greatest possible growth and this increase in value. A tree killed by the blight is still merchant- able, as the timber is not affected so far as can be determined by test. The owner of a timber lot should cut out the diseased trees, not so much to prevent the spread of the infection as to save the material already grown. In cutting a stand it is advisable to leave species other than chestnut so that there may be some reproduction by seed to take the place of the chestnut if it does not recover sufficiently to sprout. In a pure chestnut stand where the infection is bad, clearing of brush and planting with pine is the best method for keeping the area in forest. CHESTNUT BARK DISEASE. 19 SUMMARY. 1. The chestnut blight is caused by the parasitic fungus Endothia gyrosa var. parasitica and not by an insect. 2. The chestnut bark disease is slowly and surely killing the chest- nut in Connecticut, and will continue to do so unless stopped by natu- ral causes or some effective remedy can be found. 3. All methods of control that have been tried have proven only partially successful and are not practical for use in woodland. 4. It is believed that dry weather conditions have weakened the tree and enabled a native fungus to become an active parasite and that the disease has not been introduced from a foreign country. 5. If individual infected trees are cut and the bark and brush burned on the stumps, the spread of the disease may be checked, but experi- ments show that in most cases the surrounding trees are already infected, and the disease is only temporarily checked. 6. The presence of the disease in the stand in itself is not sufficient reason for cutting. Unless the trees are mature and the market con- dition is good, it is better to give the uninfected trees a chance to get all the growth possible, especially where the presence of the blight has only just become apparent. For a more detailed report on this subject the reader is referred to the Report of the Botanist, Connecticut Agricultural Experiment Station, 1911-1912. CONNECTICUT AGRICULTURAL EXPERIMENT STATION REPORT OF THE BOTANIST 1909 and 1910 G. R CLINTON, Sc.D. PAGE I. Notes on Plant Diseases of Connecticut, 713 A. Diseases in Relation to Weather in 1909 and 1910, . . . 713 B. New Observations on Diseases Previously Reported, . . 716 C. Diseases or Hosts Not Previously Reported, 723 II. Spraying Potatoes in Dry Seasons 739 III. Oospores of Potato Blight, Phytophthora infestans, 753 ISSUED JUNE, 1911 PART X. REPORT OF THE BOTANIST FOR 1909 AND 1910. G. P. CLINTON, Sc.D. I. NOTES ON PLANT DISEASES OF CONNECTICUT. A. DISEASES IN RELATION TO WEATHER IN 1909 AND IQIO. Weather Conditions in ipop. The winter of 1908-09 was not especially severe, so that trees did not show any unusual injury, except from a couple of ice storms in February, 1909. These storms so heavily coated the limbs that considerable damage resulted, especially to shade and forest 'trees in the northern half of the state, where the storm was more severe. The spring of 1909 was rather wet and backward, so that such fungous troubles as peach leaf curl, apple scab, etc., that gain their foothold at this time of the year, were unusually prominent. The summer, however, especially in July and August, like the two preceding seasons, was one of drought, but it was broken in August by rains that prevented serious damage to most of the crops. The late fall proved to be very dry. The first killing frost did not occur until October 13. Diseases Prevalent in ipop. The following troubles were conspicuous or unusually injurious during this season. Apple: Black Rot (Leaf Spot form), Rust, Scab, and Spray Injury (Bordeaux). Ash: Rust. Chestnut: Bark Disease. Egg Plant: Wilt (Fusarium?). Elm: Leaf Spot. Muskmelon: Leaf Mold, Anthracnose. Peach: Brown Rot (spring form on twigs, etc.), Leaf Curl. Plum: Black Knot. Potatoes: Tip Burn, Scab. Quince* Leaf Blight. Rose: Rust. Spinach: Leaf Mold. Strawberries: Powdery Mildew, Winter Injury (root killing). Tobacco: Calico. Of the above diseases the leaf spot of elm, which was quite serious in some places, is discussed later in this Report (p. 71?)- 50 714 CONNECTICUT EXPERIMENT STATION REPORT, IQ/DQ-IQIO. The winter seemed in some way to have weakened the spinach crojp in the vicinity of Greens Farms, for there were reports that several of the crops there failed because of the subsequent action of the leaf mold fungus described in the Report for 1905, page. 275. Mr. Joseph Adams, writing of this trouble, said : "I have a patch of spinach (sown last September in connection with Mr. L. P. Wakeman), which is practically worthless from a black spot which covers the leaves. This is the worst I ever saw. This piece contains about an acre, and we have another piece that is not quite as bad." This fungus was identified by us previously as Heterosporium variable Cke., and Professor Thaxter, who examined these later specimens, writes that it was also described by Cooke as Cladosporium subnodosum (see Grev. 17: 67. 1889). Specimens of strawberry plants were received about the middle of June, both from Essex and Naugatuck, with complaints that some trouble was killing off certain fields in those places. Examination revealed no fungus or insect as responsible, but showed that the rootlets were dead, while the crowns were still alive. This was a trouble similar to that seen once before, and discussed in the Report for 1905, page 276. Apparently there was enough life and food in the crowns to put forth leaves in the spring, but with the approach of warm weather these suddenly died off from lack of moisture, etc. The trouble seems to be due to winter injury of the roots, which had either suffered from drought the previous year or else had not been properly protected by snow or mulch during the winter. Weather Conditions in 1910. The winter of 1909-10 was not especially severe on the whole, though one or two quite cold spells were recorded in January. March proved to be unusually warm and open, and the spring started early, but afterwards cool, rainy weather in May kept back the vegetation so that, as in the preceding spring, it was somewhat backward, and developed an unusual amount of spring fungous troubles. There were two very late frosts, in May and early June, that did more or less injury to fruit blossoms in certain parts of the state, especially cherries, apples and- strawberries, and also killed or injured the foliage on certain shrubs, etc., especially in low places. At Windsor we saw small scrub oaks whose leaves were all killed as if by fire. Some injury to coniferous plants was also observed, and no doubt much of the russeting NOTES ON PLANT DISEASES OF CONNECTICUT. 715 of apples, so common this year, was traceable in part to these frosts. Again the summer proved to be one of drought, thus making four years in succession that may be so classed. However, like the preceding one, it was temporarily broken in midsummer by rains that saved most of the crops from serious injury, though potatoes, especially early varieties, were a very light crop. The fall months were unusually dry, and this late drought was not broken until late in December, so that a water famine threatened many communities. As in the preceding year, the first fall frost was delayed until the middle of October, thus favoring the late crops. Diseases Prevalent in 1910. Among the most conspicuous diseases of the year may be mentioned the following. Apple: Rust, Scab, Frost and Spray Injury. Cherry and Plum: Black Knot. Chestnut: Bark Disease, Drought Injury. Corn: Smut. Hollyhock: Rust. Maple: Leaf Scorch. Muskmelon: Mildew Blight. Peach: Leaf Curl, Brown Rot (chiefly spring infection of twigs, etc.). Pear: Scab. Pines: Pine-Sweetfern Rust. Potatoes: Rot (Blight), Tip Burn. Rye and Barley: Powdery Mildew. Quince: Rust. Sycamore: Anthracnose. Concerning the spray and frost injury of apples, there appears a discussion in Part VII of this Report. There was more peach leaf curl than we have seen before in this state, and while the wet spring favored twig infection with brown rot, this did little harm to the mature fruit except during a wet week in September, when some injury was done to certain varieties in the vicinity of Wallingford. Potatoes suffered most from tip burn, but the rains came so that blight developed slightly on the late varieties and caused some rot of the tubers for the first time in several years. Blight, in late August and early September, carried off many of the melon fields that had not been sprayed. The effect of successive droughts of the past four years has begun to be manifest on our shade and forest trees, so that an unusually large number of them are dying. This is especially true of the chestnuts, where the blight fungus plays a very important part on these weakened trees. On the whole, 1909 and 1910, because of their dry summers, were not years in which fungi became especially troublesome, 7l6 CONNECTICUT EXPERIMENT STATION REPORT, except those starting during the wet springs. In Parts B and C of this paper we discuss certain diseases that are new to the state, or concerning which special information was obtained. B. NEW OBSERVATIONS ON DISEASES PREVIOUSLY REPORTED. APPLE, Pyrus Mains. Spray Injury. Both during 1909 and 1910 there was con- siderable injury resulting from spraying apples in this state with Bordeaux mixture. As previously reported, this injury was of the nature of leaf spotting and fruit russeting. Experi- ments conducted in 1910 with different fungicides to replace Bordeaux, because of this tendency to injure, showed that there was danger of serious leaf spotting and subsequent fall with "One for All" (rate 5 or 6 Ibs. to 50 gallons of water), and also with "Sulfocide" (rate I to 200) when either Paris green or arsenate of lead was used with it, though the injury with Paris green when lime was added was lessened. Even without these insecticides, this strength of "Sulfocide" sometimes pro- duces more or less leaf spotting. Some leaf injury was also caused by Bogart's "Sulphur Compound" used at the rate of 1^2 to 50. Practically no russeting or leaf spotting was produced by any of the straight commercial lime-sulphur sprays, with arsenate of lead added, even at the rate of iJ/2 to 50, except what occasionally occurred in the shape of sun scald on the most exposed side of the fruit. While this rarely occurred, when it did it produced rather serious injury. On the whole, the straight commercial lime-sulphur sprays were the most satisfactory as regards least spray injury. For further information, see Part VII of this Report. CHESTNUT, Castanea dentata. CHESTNUT BARK DISEASE, Diaporthe parasitica Murr. In our Report for 1908, page 879, we gave an account of this trouble. At that time it had been reported in every one of the twenty-three towns of Fairfield County, and in eight towns in New Haven County, making thirty-one towns altogether. At the time of writing this article (March 20, 1911), its known distribution is as follows: Fairfield County, twenty-three towns; New Haven County, twenty-one towns; Litchfield County, NOTES ON PLANT DISEASES OF CONNECTICUT. 7J7 fourteen towns; Hartford County, seven towns; Middlesex County, two towns; Tolland County, three towns; Windham County, one town; New London County, one town. This makes a total of seventy-two towns, of which only seven are east of the Connecticut River. We have no doubt that a more thorough survey of that region would reveal its presence, in an inconspicuous way, in quite a few more towns. This increased distribution in the last three years may indicate that the disease has spread to those new localities, or it may mean that a more thorough search has revealed its presence, and that it has also become more prominent because of the four years of drought that have occurred, beginning with 1907. There are those who believe, however, that unfavorable weather conditions have nothing to do with the prominence of this dis- ease, which they suspect to be a recent importation into this country from Japan. If this theory is true, then we are just beginning to feel the effects of its devastation in this state. Personally, we have not yet found convincing proofs to cause us to change our views expressed in the above-mentioned Report. These views, briefly given, are (i) that the fungus is a native, weak parasite, usually very inconspicuous in its damage, and therefore rarely noticed; and (2) that the unusual winter of 1904, by severely injuring chestnut trees, gave it a chance to spring into unusual and sudden prominence, which it has since maintained and even increased by reason of four successive years of drought, that have injured not only chestnuts, but many other trees. We do not, and never have, questioned its seriousness. Trees that have been marked in two localities by the botanical and the forestry departments have uniformly showed injury greatly in excess of that indicated when first examined. If our theory is correct, we do believe, however, with the return of several normally wet years the trouble will gradually grow less rather than more conspicuous as it should if weakened vitality of the trees has nothing to do with its development. ELM, Ulmus americana. LEAF SPOT, Gnomonia Ulmea (Schw.) Thuem. Plate XXXIV. During the summer of 1909 several complaints came to the station of elm trees shedding their leaves where the elm leaf CONNECTICUT EXPERIMENT STATION REPORT, 1909-1910. beetle had not been at work. The most serious injury seemed to occur in the vicinity of Chapinville. At the request of Mr. Walter Angus, manager of the Scoville estate at that place, Mr. Walden first visited there in August, and as he found no insect responsible for the trouble the writer made an investigation early in September to determine if a fungus was the cause of it. By July, or earlier, some of the trees had almost entirely shed their leaves, and later put forth a new crop, and these, when examined by the writer, were quite free from fungous attack. Other trees, however* not originally so severely injured, showed the leaves quite badly infected with the above fungus, and these had been shedding their leaves more or less during the season. Where the defoliation had been rather severe, the young branchlets of the season had also frequently fallen off. While the fungus was present on some trees more than on others, and while some of the fallen leaves showed no sign of the fungus, it seemed quite evident, after a careful examination, that this fungus was primarily responsible for the trouble, but that drought had helped to exaggerate it. The illustration shows the condition as regards foliage of one of the trees photo- graphed by Mr. Walden in August. The fungus produces very numerous, small, black eruptions on the upper surface of the leaves, and these often merge more or less in small groups. In time the specimens show a whitish or grayish margin around these black cushions, due to the wearing away of the epidermis. We have been unable to find any fruiting stage in any of the specimens we have gathered in different years, as the only known stage produces its asco- spores on the fallen leaves the subsequent spring. Infection seems to take place only early in the season, since the trees early denuded did not have their second crop of leaves attacked to any extent. Apparently the weather conditions in the spring determine the character and amount of infection, and these conditions seem to have been unusually favorable in 1909. In 1910, on the same estate in Chapinville, the fungus did practi- cally no harm, though the trees bore a smaller crop of leaves, due to the shedding of the small twigs the previous year and to the death of others that were severely injured. Spraying the unfolding leaves with Bordeaux would probably control this trouble, though the uncertainty of its appearance would make such a treatment rarely practical. NOTES ON PLANT DISEASES OF CONNECTICUT. 719 This fungus was placed by Ellis under the genus Dothidella as D. Ulmea (Schw.) E. & E. It is, however, quite distinct in its microscopic appearance, as Ellis states, from Dothidella Ulmi (Duv.) Wint, although the two have ascospores very similar. The latter fungus has its perithecia embedded in a distinct black stroma, and the necks open on the upper surface of the leaves. The former, by the crowding of the perithecia together, has something of the appearance of an imperfect stroma, while the perithecia open on the under surface of the leaves mature their asci later, and apparently have no other stage connected with them. HEMLOCK, Tsuga canadensis. HEMLOCK-HEATH RUST, Pucciniastrum Myrtilli (Schum.) Arth. (I. Peridermium Peckii Thuem.) The T stage of this fungus (see Report 1907, pp. 350, 383), which is not uncommon, though rarely abundant, in this state on hemlock, has now been connected by us, through artificial infections, with the II and III stage of the above Pucciniastrum, which we found in 1910 for the first time on various species of blueberry and huckleberry. Pucciniastrum minimum on cultivated azaleas, also found here (see Reports 1907, p. 392 and 1908, p. 854), is probably not distinct from this Pucciniastrum. PEACH, Prunus Persica. Spray Injury. Sturgis (Report 1900, p. 219) has recorded spray injury to the foliage of peach by Bordeaux and other fungicides used in his experiments to prevent peach rot and scab. He found potassium sulphide to be about the least injurious fungicide when used at the rate of I Ib. to 50 gallons of water. In our experiments with spraying peaches in 1910, this strength was used, and very little injury, except shot-holes in a few of the leaves, resulted/ However, when arsenate of lead (rate of 3 Ibs. to 50 gallons potassium sulphide) or Paris green (i Ib. to 100) was added, the most serious injury resulted. Not only were the leaves badly injured by shot-holes, but in time they all fell off. Many of the young twigs were also badly spotted (purplish spots much like those produced by the scab fungus), and some were killed. A few young trees were so severely injured that they finally died. 720 CONNECTICUT EXPERIMENT STATION REPORT, 1909-1910. Very similar results were obtained when either of these insecti- cides was used with "Sulfocide." This spray, even when used without them, at a rate of I to 200 produced more or less injury, and even some on young trees at I to 400. With both potassium sulphide and "Sulfocide" the injury resulting from the addition of the poisons was due to the production of a soluble arsenate which burned the tissues. PINE, WHITE, Pinus Strobus. So-called "Blight" In our "Report for 1907, page 353, we described the white pine ' 'blight," which was general that year not only in Connecticut but all over New England. We took the view that it was a physiological trouble due to adverse weather conditions (such as winter, drought, and frost injuries), though there were those who believed that it was of a contagious nature, due to fungous attack. We now have data at hand to prove that we were correct. In general this disease becomes evident by the leaves being killed to a greater or less extent from their tip downward, the dead portion turning reddish brown, and also by the undersized leaves, which remain bunched, due to the failure of the branches to lengthen out. That the disease is not contagious was suggested strongly in our previous studies, since leaves on one tree may all be badly affected while those of an adjacent tree show no signs of the trouble. This noncontagious nature has been clearly proved by observations made in the station's forest plantation on a lot of white pine trees eight years old, in 1910, from planting. At our request the forester, Mr. Hawes, early in the spring of 1908 had all the diseased trees of this plot marked by permanent stakes. There were one hundred and twenty-four of these so marked, but it seems quite likely that some few that showed the disease slightly at the time were not included. We examined them that fall, and found that their condition on the whole seemed somewhat improved, and that there was no general increase of the trouble, though some trees that had not been marked showed signs of the disease. In July, 1909, and again in November, 1910, careful examinations were made of the plot, and the condition of each diseased tree noted. The com- parative condition of these trees as regards foliage is shown in the following table: NOTES ON PLANT DISEASES OF CONNECTICUT. 72 I Diseased, but Date of not marked Not Examination in 1908 Dead Improved Improved Cured Total July, 1909 24 5 54 38 21 142 Nov., 1910 18 6 9 65 44 142 This shows that there has been gradual improvement since the trouble first showed in 1907, and that there has been practi- cally no subsequent spreading of the trouble. That is, in 1910 there were only eighteen trees showing the disease, among the 3,000 to 3,200 in the plot, that did not show it in the spring of 1908. Of these eighteen, at least thirteen were included as questionable; that is, there was not positive evidence that it was this trouble, as the leaves were only slightly affected. No doubt, too, some of these were trees that were not marked originally because they were not badly injured. It is also quite probable that some were trees whose leaves were injured by the frosts of 1910, of which we shall speak later, as the injured leaves were often largely on lower branches. Finally, there was no relationship in position between these trees and those badly diseased. Concerning the effect of the so-called "blight" on the sub- sequent growth of the trees, we may state that those that were very badly injured have either died, or remained so stunted in growth that their subsequent usefulness is quite doubtful. Others that were rather severely injured have made some growth, and their foliage condition, especially as to color, has improved considerably, though the leaves often remain more or less stunted and bunched. Those least injured have recovered their normal leaf appearance, but are still somewhat backward in their growth. Some few seem to have almost entirely recov- ered from the effects, and are scarcely to be distinguished in size and appearance from the surrounding trees that were not injured. Concerning the cause of the sudden appearance of this "blight" in 1907, we are now quite convinced that it was due to the severe frosts that occurred on May 11 and 21 of that year. We mentioned these as a possible cause in our previous Report, but at that time we had no proof as to their connection, as the "blight" was not called especially to our attention until August. In 1910, however, we saw the same trouble produced on certain pines by the late frosts of May and June of that year. Soon after these frosts we found the leaves of scrub 722 CONNECTICUT EXPERIMENT STATION REPORT, oaks in certain regions entirely killed by the frosts, just as had been the case with the leaves of sycamore trees in 1907. In 1910, however, the frosts were much more local in their effects, and in a given region often killed the leaves only on the lower trees and the shrubs, especially those in low places. Shortly after the last of these frosts we visited the white pine planta- tions on the Whittemore estate at Middlebury, and here we found not only small oaks and other trees in low spots with injured foliage, but also the young pines in these low places showed "blight" injury on the tips of their leaves. Often a difference of only a few feet in the level of the ground on which these stood determined whether or not they were injured. We have also noted elsewhere in this Report injury by these frosts to pine seedlings in the seed beds. Whether or not a pine tree is injured by the late frosts seems to be determined by the state of development of the foliage at the time, as well as by the lay of the land and the character of the frost. Previous to 1907 we had some few complaints of pine "blight," which we may attribute to winter injury of the roots, and no doubt drought or other injury to the roots, if severe, produces a similar effect. Hartig, in his Diseases of Trees, English ed., p. in, notes a similar "blight" trouble in Europe, due to frost and drought injury. PLUM, Prunus sp. BACTERIAL SPOT, Pseudomonas Pruni Sm. This has been reported here before on peach, causing spots on the leaves, and on the plum, causing large black spots on the fruit. In July, 1910, it was seen at the Ives farm, Meriden, for the first time causing a shot-hole spotting of plum leaves, similar to that not uncommon on the peach. SPRUCE, NORWAY, Picea excelsa. Smoke Injury. During the summer of 1910 the writer saw young spruce trees at East Rock Park, New Haven, that had been injured by smoke from a brick kiln about half a mile distant. The injury occurred suddenly on a day when the atmos- pheric conditions were just right for blowing the smoke among the trees. The young leaves of this year were killed and sub- sequently dropped off, but those of the previous year were NOTES ON PLANT DISEASES OF CONNECTICUT. 723 not injured. Some other conifers were also slightly injured, but the deciduous trees escaped injury, though in the vicinity of the kiln the maples and other trees are sometimes injured. Previous smoke injury, complicated with drought injury, to asparagus fields in the vicinity of this kiln, was mentioned in our Report for 1908, page 858, and similar injury is claimed to have been caused again this year. C. DISEASES OR HOSTS NOT PREVIOUSLY REPORTED. APPLE, Pyrus Malus. Fruit Spot, Cylindrosporium Pomi Brooks. Plate XXXIII a. In our Reports for 1905, page 264, and 1907, page 340, we described a fruit speck of apples that formed small, brownish, spots in the skin of apples, being especially prominent after stor- age. Cultures proved this trouble to be of fungous origin, but as these cultures did not produce a fruiting stage of the fungus, we were not sure of its identity. More recent study has shown that there are three fungi that occur in fruit spots or specks of apples. One of these is the black rot fungus, Sphaeropsis Malorum, which is more commonly known not as a spot trouble, but as a general rot of the fruit, especially on summer and fall varieties following insect injury. This fungus is the one that we have most commonly isolated from the fruit specks of market apples. Ordinarily it does not fruit in the culture media on which we have grown it, and so it was probably largely responsible for the fruit speck we describe in the above reports, though Cylindrosporium Pomi was possibly present in some cases. Besides the black rot, we have also occa- sionally isolated a species of Alternaria which seems to be respon- sible for speck injury, though we have as yet made no inoculation tests to prove this. The third fruit spot, which we have seen frequently on the fruit before it was gathered from the trees, as well as afterwards, is that caused by Cylindrosporium Pomi, which was described a few years ago as a new species by Brooks, who found it respon- sible for a serious spotting of apples in New Hampshire. This fruit spot on the market apples is usually very difficult to distin- guish from that of the black rot. Perhaps the black rot fungus 724 CONNECTICUT EXPERIMENT STATION REPORT, may finally crowd it out in many cases. However, on certain light skinned varieties, especially seedlings, it shows in the summer as small spots in the skin having a decidedly pinkish or reddish purple color. We have seen roadside seedlings made very con- spicuous by it in late fall. In storage the color of the spots is darker. So far we have not seen the fungus in fruit on these superficial spots, and ordinarily they do not seem to reach any considerable size, except perhaps when developed further by the presence of the black rot fungus. In one instance we isolated this Cylindrosporium from market quinces, a new host, and we have frequently seen similar spots, showing no fruiting fungus, on quinces before and after picking. On our oat juice agar medium the fungus forms a large, yeast- like, pinkish colony with no aerial growth, but producing an abundance of spores. With age it turns a darker color, sometimes black, though in such cases it may be due to the presence of another fungus frequently associated with it, which we have isolated, but whose identity has not yet been determined. AZALEA, Rhododendron indicum. POCKET CURL, E.vobasidium Vaccinii (Fckl.) Wor. Plate XXXIII b. Galls and hypertrophy caused by this or closely related species are not uncommon in this state on various wild species of the heath family, but this fungus on a cultivated species was called to our attention for the first time in the fall of 1909. Specimens of the above azalea, purchased a few months previously for a private greenhouse, were very badly injured. These plants were apparently infected when purchased, having been grown out of doors in a neighboring state, but did not show the trouble at that time. The disease appeared on the leaves, usually involving the apical part and causing a decided thickening of the tissues. This infected part covered more or less of the leaf, which often became decidedly concavo-convex, as shown in the illustration. The infected tissues were quite sharply marked off from the healthy part, both by their dis- tortion and by their whitish color, being eventually covered by a mealy coating of spores, etc. Cultures were made, and a fungus obtained that seems to be a conidial stage of this fungus, though its identity has not been thoroughly established. NOTES ON PLANT DISEASES OF CONNECTICUT. 725 The question whether or not the various forms of Exobasidium found on the different genera of the heaths are distinct or not has not been definitely decided. Often their macroscopic appearance on different hosts is quite distinct, but as Richards (Bot Gaz. 21 : 101. 1896) succeeded in producing the ordinary leaf form from spores of the unusual large bladder form on a different host, it looks to the writer as if these differences were largely due to the age or parts of the host infected. Shirai has described two species of Exobasidium on Rhododendron indicum, to one of which our fungus possibly may belong if they are really distinct, though the spore measurements do not seem to agree entirely. CELERIAC, Apium graveolens var. rapaceum. LEAF BLIGHT, Cercospora Apii Fr. We have reported before, on ceieriac, the leaf spot due to Septoria, but not this fungus. Both produce brownish or grayish spots of considerable size on the leaves, often causing them to turn yellow and die pre- maturely. They are often found associated, the Cercospora being distinguished by its minute threads arising from the surface of the leaves, while the Septoria forms small, embedded, black specks. CHESTNUT, Castanea sps. CHESTNUT BARK DISEASE, Diaporthe parasitica Murr. Speci- mens of this serious disease of our native chestnuts have been collected on the Japanese chestnut, Castanea japomca, in a local nursery. Dr. R. T. Morris, who grows a large number of varieties of chestnuts on his Stamford farm, also reports (Conn. Farmer, March n, 1911, p. 2) that, besides the Japanese species, the European species, Castanea sativa, and the American Chin- quapin, Castanea pumila, have been more or less subject to this blight at this place. See page 716 of this Report. CHESTNUT, Castanea dentata. POWDERY MILDEW, Microsphcera Alni (Wallr.) Wint. We have not reported this host because we have found the mildew on it previously only in the woods, but in September, 1907, it was observed on cultivated trees in a small nursery at Storrs. It forms evident, mealy, whitish growths, in which the perithecia 726 CONNECTICUT EXPERIMENT STATION REPORT, 1909-1910. are embedded as small black specks, chiefly on the upper surface of the leaves. It is not an important disease of this host. CHIVES, Allium Schcenoprasum. RUST, Puccinia Porri (Sow.) Wint. This rust was collected by Dr. Britton during June, 1910, on chives in his garden in Westville, where it was doing considerable injury to the plants. Both the II and III stages were present, the former showing as minute, reddish, dusty pustules, and the latter as black, granu- lar ones, more permanently covered by the epidermis. The leaves, when fairly abundantly infected, turned yellow and died prematurely. I have not seen any account of injury by this rust to cultivated species of Allium in this country, though in Europe it is not uncommon. Worthington Smith, in his Dis- eases of Field and Garden, page 39, mentions it, under the name Puccinia mixta Fckl., as causing serious injury to a crop of chives in England. There is more or less difficulty in deciding the proper genus of this fungus, since the telial spores in some specimens on certain hosts are almost or entirely single-celled, and so properly come under the genus Uromyces; other speci- mens show these spores largely two-celled, and so place it more properly under the genus Puccinia. Our specimens run more nearly to the former type, as not over one or two per cent, of the spores are two-celled. Winter considered the two as a single species, and we have followed him. Other writers place the single-celled form under Uromyces ambiguus (DC.) Fckl., and the form with most of its spores two-celled under Puccinia Porri, as given here. The rust on chives in Europe is generally reported under this latter name. Our specimens, however, have fewer two-celled spores than those we have seen from Europe on the same host. Puccinia Allii (DC.) Rud., also on species of Allium, is quite a different fungus. CORNFLOWER, Centaurea Cyanus. RUST, Puccinia Cyani (Schl.) Pass. Both the II and III stages of this rust were found, causing severe injury to the cornflowers in the writer's garden during the summer of 1909. The sori, while numerous, form rather inconspicuous, dusty outbreaks on both surfaces of the leaves and on the stems NOTES ON PLANT DISEASES OF CONNECTICUT. 727 Apparently this fungus has rarely been reported in this country. Another rust, P. Centaurea DC, also occurs on other species of Centaurea both here and in Europe. Both of these species have frequently been grouped with other Puccinias, the species here reported being usually placed under P. suaveolens, along with the rust on Cnicus now commonly known by that name. ELM, Ulmus sp. ANTHRACNOSE, Septogl&um Ulmi (Fr.) Br. and Cav. This fungus was found on an escaped seedling of Ulmus campestris (apparently) along the roadside in Centerville. It produces numerous, minute, at first yellowish but finally reddish-brown spots on the upper surface of the leaves, while below the fruiting stage shows as minute, glistening, yellowish globules. The fungus has usually been reported as Phleospora Ulmi (Fr.) Wallr., but the writer agrees with Briosi and Cavara that it belongs more properly under the above genus. Cylindro- sporium ulmicolum Ell. and Ev. possibly is not distinct from this species, as its description is very similar. This Septoglceum is thought by some writers to be the spermagonial and Piggotia astroidea B. and Br., the pycnidial stage of Dothidella Ulmi (Duv.) Wint. [Phyllachora Ulmi (Duv.) Fckl.], though neither of these two stages were found associated with our specimens. The asco stage of Dothidella Ulmi, while not uncommon in Europe, does not seem to have been reported in this country except the doubtful specimen sent by Torrey to Schweinitz. GOOSEBERRY, Ribes sp. RUST, 2£cidmm Grossularice (Pers.) Schum. This rust was found on the leaves of a species of gooseberry, apparently escaped from cultivation, in the woods of an abandoned farm belonging to the water company at Ansonia. The fungus forms rather small clusters of cup-shaped fruiting bodies on the under surface of the leaves, producing discolored spots above. It is probably connected with some species of Puccinia on Carex as its mature stage, as has been found to be the case with several European forms on Ribes sp. We have never seen this TEcidium causing much harm to its hosts, and it seems to occur chiefly on the wild species. 728 CONNECTICUT EXPERIMENT STATION REPORT, 1909-1910. HORSECHESTNTJT, JEsculus sps. POWDERY MILDEW, Uncinula flexuosa Pk. This mildew was found on a species of ^Esculus with colored blossoms, on an estate at Chapinville in the fall of 1909. The conidial stage formed a conspicuous whitish coating on the upper surface of the leaves, while the perithecia were less prominent, though abundant, on the lower surface. The fungus has not been reported by us before, though Thaxter collected it in New Haven in 1888 on another Cultivated species, ^Esculus Hippo- castanum. MONKSHOOD, Aconitum Fischeri. STEM ROT, ? Hypochnus sp. In our Report for 1907, page 351, we described this stem rot, which was found on a variety of herbaceous plants in a local nursery. This year it was sent to us from Westbrook, where it was injuring specimens of larkspur, one of the hosts reported before. Since our first report we have also found it on monkshood, in the same nursery where it was found originally. So far we have been unable to identify the fungus, as our cultures form only the sclerotial stage — small, reddish, usually subspherical bodies about 2 to 5 mm. in diameter. We have a similar fungus from potato stems, forming considerable small sclerotia, that was given to us by Morse of the Maine Station. While in Japan, we saw in Professor Hori's laboratory artificial cultures of a number of these sclerotial fungi, which he had described as species of Hypochnus, though we are not sure of this identification from what we have learned concerning them. PINE, Pinus sps. PINE-OAK RUST, Cronartium Quercus (Brond.) Schroet. (I. Peridermium cerebrum Pk.) On specimens of jack pine, Pinus Banksiana, in the nursery of the station forest plantation at Rainbow in the spring of 1910, Mr. Filley, and later the writer, collected the I stage of this fungus. These seedlings were about four years old, and had been brought in 1908 from Michigan, where no doubt they were originally infected, as this fungus in none of its stages has ever before been found in this state. The fungus on the pine forms conspicuous NOTES ON PLANT DISEASES OF CONNECTICUT. 729 swellings, usually globular in shape, and in early spring the fruiting stage shows under the denuding bark as orange-colored, dusty spore masses, with the peridia rarely forming distinct cups, as in the next species. The II and III stages occur on species of oak. So far as could be seen, these did not appear on the oaks in the vicinity, and as all the infected pines were destroyed, it is not likely to become established there. Infec- tion experiments made in the laboratory from the I stage, however, produced the III stage only very readily on seedlings of both red and white oaks. So far this fungus has not done much damage elsewhere on either host. See Plate XXXVI b. PINE-SWEETFERN RUST, Cronartium Comptonice Arth. (I. Peridermium pyriforme Pk.) In the Report of 1907, page 380, the writer reported the I stage of this rust on both Pinus rigida and P. sylvestris from this state. It had become established on the latter host in the station forest plantation at Rainbow. In 1910 it was found there also on Pinus rigida, P. austriaca, and P. maritima. It was also found in its II and III stages on the sweetfern, to which it had spread since its introduction. Apparently most of these pines had become infected in their nursery beds at Poquonock before transplanting here some years ago, as thousands of seedlings of Pinus rigida grown from the first in their vicinity showed practically no infection. The specimens of P. maritima, however, had become infected there in their seed bed, yet we could find no infected sweetfern in their immediate vicinity this year. In order to prevent further spread of the rust, all infected pines were destroyed or the infected branches cut off, and the forester had all the sweetfern in the vicinity mowed off. Most of the pines, having the fungus on their main trunk, were of little value. Where infection takes place after the pines are a few years old, the damage is not likely to be nearly so severe as when it takes place in the seed bed. See Plate XXXVI c. PINE, WHITE, Pinus Strobus. Drought Injury. In the fall of 1909, Mr. Spring noticed a few spots in one of the seed beds at the station forest plantation where the white pine had been entirely killed out for the space of a few inches. Specimens of these and some of the adjacent living pines were brought to the writer at the time for examina- 73° CONNECTICUT EXPERIMENT STATION REPORT, tion. On the stems of :the dead pines, and also somewhat on the living ones, was a conspicuous felt of mycelium of a hymenomycetous fungus which Professor E. A. Burt determined as Coniophora byssoidea (Pers.) Fr. At first we thought that this fungus was responsible for the death of the seedlings, but we were unable to find any account of injury caused by it elsewhere. A bunch of these young pines was kept in a crock in the greenhouse for several months, and there was no indi- cation that the fungus injured the healthy young pines on which it originally occurred, or that it spread further. The fungus evidently ran up on the stems merely as a saprophyte, from various leaves on the ground on which it also occurred. The pines in the seed beds were probably killed by the drought, which was so severe in 1909, and the dead and injured seedlings offered a better condition for the development of the fungus than the surrounding mulch of leaves, as Professor Burt states that out of nine specimens in his herbarium seven are on pine and two on spruce. See Plate XXXV a. Frost Injury. Plate XXXV b. In examining the seed beds of white pines at the station plantation at Rainbow in the fall of 1910, the writer found small spots scattered in the beds where the leaves of this year's growth had been killed. The injury was evidently caused by the late frosts of May and June of that year, as these had killed the leaves of the scrub oaks in this vicinity, as observed at the time. The young pines had developed their terminal branches an inch or two in length, and these had been severely injured or killed by the frost on both the one- and two-year-old seedlings. The leaves of the previous year remained uninjured. Afterwards these injured pines put out several lateral buds from or below the injured tip, but even as late as November i, when seen by the writer, these had not usually attained a length of half an inch. This injury had severely stunted the growth of the plants during the season, as is indicated by the photograph, which shows one of the uninjured plants, besides several of the injured ones of the same age. A few seedlings of Pinus montana were also injured, but not so extensively as were those of the white pine. PINE-CURRANT RUST, Cronartium ribicola Waldh. (I. Peri- dermium Strobi Kleb.) Plate XXXVI a. In our article on Heter- cecious Rusts of Connecticut, published in the Report for 1907, NOTES ON PLANT DISEASES OF CONNECTICUT. 731 page 374, we mentioned this rust as one likely to be brought into this state on imported white pine seedlings from Europe. Its introduction really occurred sooner than was anticipated. Mr. F. A. Metzger first found specimens on a lot of three-year- old seedlings from Germany that had been imported by our State Forester for Mr. C. F. Street, and planted at Wilton. Mr. Metzger, who was employed to set them out, found in the 10,000 seedlings from fifty to one hundred that were infected with the rust. He brought specimens to the station the last of April, 1909, but as the writer was in Japan at that time, nothing further was done. In the meantime Messrs. Metcalf and Spaulding, of the U. S. Department of Agriculture, who had been looking up infected seedlings in other states, came to this state about the middle of June, and with the forester examined the plantations of the New Haven Water Company at West Haven and the Ansonia Water Company near Ansonia, and found a few very suspicious specimens at these places. Arrangements were made soon after- ward by which Mr. Spaulding and Mr. Graves for the Govern- ment and the botanical department for the station undertook during July to go over the plantations in the state where white pine seedlings had been imported from Europe, and inspect them for this rust, and to destroy any infected seedlings, if found, and any wild gooseberries or currants in their vicinity, as the II and III stages occur on the latter as alternate hosts. It was really then too late in the season to find the fungus on the pines, except far past its prime. However, twenty-four plantations, including about 580,000 seedlings, were inspected, and very suspicious or positively identified infected specimens were found at two additional places; viz., at the Plant estate plantation at East Lyme and at the Groton Water Company plantation at Poquonock. In none of the five places where signs of the pine rust were found were more than a dozen specimens seen, except at the Street plantation, where the dis- eased plants were noticed as they were being set out. A descriptive letter concerning the rust and its reputation was sent to all those who had used imported seedlings. In 1910 the botanical and forestry departments of the station undertook to again go over these and other plantations, beginning early in the season, as soon as the rust ordinarily makes its 732 CONNECTICUT EXPERIMENT STATION REPORT, IQ/X^-IQIO. appearance. During May and June four inspectors visited twenty-six plantations, inspecting about 425,000 seedlings, and made very careful examinations for the rust, in many cases examining every individual seedling. In spite of this thorough examination, not a single rusted plant was found! No doubt the severe drought of the preceding year had killed off those seedlings weakened by the rust, if such existed. Of course it is possible that examination another year might reveal a few rusted plants, as it is usual for the seedlings to go one or possibly more years after infection, before the secial stage of the rust appears on them. During the years 1907, 1908 and 1909, there were imported into the state, chiefly from Germany, under the supervision of the station's forestry department, about 640,000 white pine seedlings, which were set out in fifty-five different localities, and private individuals have imported at least 100,000 more. All of these seedlings, except about 95,000 set out mostly in small lots in twenty different localities, have now been inspected once or twice for the rust. No doubt, too, at the time they were set out the men would have discarded any specimens showing evidence of the rust. In all of the plantations exam- ined, watch was kept for any signs of currants or gooseberries in the vicinity of the pines, and these were destroyed when found. Fortunately, species of Ribes in a wild or escaped state are comparatively rare here, so that even if this rust occurred on the pines, it would be much more difficult for it to pass to these hosts than in some of the more northern states where they are more frequent. In 1910 the station did not import any white pines because of the danger of bringing in this rust, and only one lot, to our knowledge, was imported by others. Examination of these showed no signs of the rust. From now on it is probable that most of the seedlings set out will be native grown stock, as plenty of this seems to be in evidence at fair prices. There does not seem to be much likeli- hood, therefore, that the rust will obtain a foothold in the state, though watch will still be kept for it. Anyone finding suspicious specimens should send them to the station for exami- nation. Infected white pine seedlings, out of the season when the fruiting stage appears, may be recognized in a general way NOTES ON PLANT DISEASES OF CONNECTICUT. 733 by the somewhat fusiform swollen stems and by the bunching of the leaves, shown by the halftones in Plate XXXVI a. Not all swellings of the stem, however, are due to rust, as insect and other injuries may produce such distortions in young seed- lings. During the months of May and June the fruiting stage shows on the swollen stems as small, white, oblong blisters that upon rupture reveal an orange mass of spores. These gradually wear away, and then positive evidence of infection is more or less difficult. The mycelium remains in the infected tissues, gradually spreading to the new growth, and renews its fruiting stage each spring, unless the death of the host intervenes. The spores produced on the pine do not spread the disease to other pines, but develop two other spore stages on both goose- berries and currants, the last stage carrying the fungus back to the pines. Many writers consider this rust as a very serious menace to white pines. The writer is not so much afraid of it in this state because of the scarcity of the alternative hosts, and also because it looks to him as if most of the damage comes from the use of infected seedlings, which we should be able to largely eliminate here. Such infection as might occur after the pines once got a good start in the forests we are inclined to believe would be rare, and not nearly so injurious to the host. We have heard of one large importer of white pines who intends also to import a large number of currant bushes for commercial purposes. Such a condition offers a chance for the rust to do considerable harm if it once gets started in -either of his plan- tations. The native pine-sweetfern rust, which we describe elsewhere, seems to us to be just as virulent as this rust, and one much more likely to spread generally here, on account of the frequency of its alternate host, the sweetfern. Yet, with the exception of the plantation at Rainbow, where pines were infected in the seed beds, we have seen and heard of no damage by this rust. This rust does not occur on the white pine, though it has several other species for its hosts. PRIVET, Ligustrum vulgare. ANTHRACNOSE, Glceosporium cingulatum Atk. Mr. Coe, of the Elm City Nursery Company, first called the writer's attention 734 CONNECTICUT EXPERIMENT STATION REPORT, to this disease on a variety of privet called italicum, which was imported from France in the spring previous to our examination in the fall of 1910. The fungus causes diseased areas on the stem and branches, which are not very conspicuous, being slightly sunken and a different color, but when these cankers entirely girdle the branches, the leaves and finally the whole branch above die, and the trouble becomes very evident. The injury at this place was quite noticeable, through the dead branches and one or two dead bushes, but probably the shock of transplanting may have weakened the plaftts so that the trouble was more conspicuous than it would be under more favorable conditions for the host. When Atkinson originally described this fungus (Bull. 49, Cornell Exp. Sta.) in 1892, he said nothing about the injury to the host, and we have seen no reference where it is said to have caused conspicuous injury, though it seems to be capable of it. Atkinson obtained cultures of the fungus, described the conidial stage, and suggested that it had a mature stage, which his student, Miss Stoneman, later described (Bot. Gaz. 26: 101. 1898) as belonging to the genus Gnomonwpsis, now known as Glomerella. Cultures of the fungus were easily obtained by the writer from the cankers, and these produced both the conidial and the asco stages. Miss Stoneman notes the presence in the cultures of setae connected with the conidial stage, but did not find these on the host. The writer, however, found some of these setae with the conidial stage on the host. EASPBEEEY, Rubus strigosus. RUST, Puccinastrum arcticwn var. americanum Farl. This rust, which was described a few years ago by Professor Farlow (Rhodora 10: 13. 1908), has ordinarily been confused with the uredo stage of Kueneola albida, as, like that species, it forms very small orange outbreaks on the under side of the leaves. Microscopically, however, the two are quite distinct. The uredo stage was sent to the writer from Stamford in September, 1909, on cultivated raspberry, this being the first time it has been found in the state. It apparently did little harm to its host. The secial stage is unknown, though it may be Peridermium balsameum on the balsam fir. NOTES ON PLANT DISEASES OF CONNECTICUT. 735 RYE, Secale cereale. POWDERY MILDEW, Erysiphe graminis DC. In our Report for 1903 we listed the conidial stage of this mildew on cultivated barley. In 1910 specimens on rye were received from J. F. Shepard, of New Haven, and others were collected by the writer at the station farm at Centerville, these being the first collections on this host in the state. In the latter locality the perithecial stage was very conspicuous and abundant on rye, but on barley was practically absent. Considerable injury was caused to both these hosts through severe infection of the leaves, which died prematurely. Apparently the season was favorable for an unusual development of the fungus. It forms an evident grayish felt in small clusters, thickly covering the leaves, and the perithecia, when produced, show as small but evident black specks embedded in this. As usual with this species, none of the asci matured their spores on the living plants. SQUASH, Cucurbita Pepo. Chlorosis. In previous Reports we have mentioned chlorosis troubles of Lima and string beans, muskmelon, tobacco and tomato. Of these so far we have been able to prove only those of tobacco and tomato to be infectious, that is, capable of producing the trouble in healthy plants when juice from the chlorosis plants is placed on the young leaves. In June, 1910, we saw plants of summer squash in cold frames at the Farnham farm in Westville that were subject to a chlorosis trouble, though from its appearance it did not impress us as being of an infectious nature. The leaves were quite prominently streaked with irregular areas of lighter yellowish-green, the normal green color remaining more commonly around the veins. The cause of the trouble was not determined, though possibly too much manure in the beds may have had something to do with it. SWEET PEA, Lathyrus odoratus. POWDERY MILDEW, Erysiphe Polygoni DC. Previous to this we have reported in this state only one trouble of the sweet pea ; viz., a rot disease. This powdery mildew forms a mealy, whitish growth on the leaves through the production of its conidial stage, but the perithecial stage was not found. Apparently the 736 CONNECTICUT EXPERIMENT STATION REPORT, 1909-1910. mildew is not a conspicuous parasite of the sweet pea, as it is not listed on this host in the more prominent works on the mildews. The absence of the mature stage renders its deter- mination somewhat doubtful, but as the conidial stage agrees with the above species, and as this has been reported on several other species of Lathyrus, it is more likely to be this than any other species. WALNUT, ENGLISH, Juglans regia. WHITE MOLD, Microstroma Juglandis (Ber.) Sacc. We have reported this fungus before on cultivated specimens of our native butternut. It was sent to the writer in July, 1909, by Dr. R. T. Morris on the variety Kaghazi of the English walnut, grown on his farm at Stamford. While this fungus forms conspicuous white patches on the under sides of the leaves, it is not usually a very serious pest. WHEAT, Triticum vulgare. STINKING SMUT, Tilletia fcetens (B. and C.) Trel. Very little wheat is grown in this state at the present time, so that this smut has not been collected here in the fields. However, it is of economic importance in another way. At least four times during the last few years samples of commercial wheat feeds, usually in the shape of middlings, have been sent to the station for examination because animals refused to eat the feed. Two of these samples have come from feed men and two from farm- ers. A microscopical examination in each case has shown the presence of the spores of the stinking smut. In a sample recently received from Mr. R. A. Jones of Bethlehem, the smut spores were unusually abundant. Mr. Jones said that the mid- dlings had been fed to hogs, that it made them sick, and that some of them refused to eat more. After changing to other food the hogs got over their trouble. Feeds that contain these spores indicate not only that they are made from middlings, but from badly smutted or injured wheat, which would be of no value for flour. Whether or not the smut spores are themselves the injurious principle might be questioned, but there seems to be no question, if they are not, that the action of this fungus, or its opening the way for NOTES ON PLANT DISEASES OF CONNECTICUT. 737 bacteria to act, produces in the plant tissues deleterious products that injure or render dangerous their use for feeding purposes. Tubeuf, in the English edition of his Diseases of Plants, page 306, says concerning Tilletia Tritici (a very closely related smut, also found in grain in this country) : "The smut also possesses poisonous properties which make flour contaminated with it dangerous to human beings and the straw or chaff injurious to cattle. . . . The symptoms in the few cases of disease observed do not agree very closely. A paralyzing effect on the centers of deglutition and the spinal cord seem to be regularly present. As a result one generally finds a continuous chewing movement of the jaws and a flow of saliva, also lameness, staggering, and falling. Cattle, sheep, swine and horses are all liable to attack." McAlpine, in his Smuts of Australia, page 81, records a case in which six hundred and fifty Leghorns dropped in a few days from a daily average of one hundred eggs to sixteen when they were fed on smutted wheat, and when this was stopped and clean wheat substituted, they regained in three weeks an average daily yield of eighty eggs. He also records an experiment with pigeons in which one pair was fed smutted wheat for twenty- two weeks, while the other pair was fed sound wheat. The doves fed good wheat laid seven eggs during this period, while the others laid only two. Both pairs of pigeons at the start were in good plumage, and the pair fed on good wheat retained the good plumage and was fat at the end of the experiment, while the other pair was in poor condition, with the feathers all standing out. While writing on this subject of deleterious animal foods, we might mention that we have also occasionally had whole oats sent in that horses refused to eat. We have never found any fungus that might be the cause of a musty condition of these oats. It has been thought that in these cases the oats were bleached by some sulphur process, and that this had left them unpalatable to the horses. We have also recently heard of a case where certain farmers last year purchased oats for feeding purposes, and as they looked plump and white they were also used for seed. None of the fields sowed with these oats came up, and as they were to serve as a cover crop for grass seed, the latter also failed. It seems quite probable that 73^ CONNECTICUT EXPERIMENT STATION REPORT, IQOQ-IQIO. these oats had been sulphured, and their vitality entirely destroyed. Seed at all suspicious should be sent to the station to have its germination tested. We have also had one or two cases called to our attention recently where animals have been made sick and some have died from eating silage. In such cases the silage had not been properly made and had become moldy, and the fungous growths no doubt had produced poisonous products in the decomposition of the silage. Similar troubles have been noticed elsewhere from feeding moldy silage (see Pammel's Manual of Poisonous Plants, p. 24). PLATE XXXV. a. Drought injury, followed by fungus, p. 729. b. Frost injury, p. 730. Healthy INJURIES OF WHITE PINE SEEDLINGS. PLATE XXXVI, a. Pine-Currant Rust, p. 730. b. Pine-Oak Rust, p. 728. c. Pine-Sweetfern Rust, p. 729. STEM RUSTS OF PINES. PLATE XXXVIII a. mycelium; b. oogonial thread ; c. oogonium ; d. oosphere ; e. oospore ; f. antheridium. DEVELOPMENT OF OOGONIA OF PHYTOPHTHORA INFESTANS, p 769. PLATE XXXIX, A-F. Mature oogonia, oospores and antheridia of P. infestans, p. 770. G-I. Oogonia-like bodies found in blighted leaves and tubers of potatoes, p. 756. J. Oogonia of P. caclonim and K, hybrid of this and P. infestans, p. 773. OOHONIA OOSPDRFS ANTHFRIDIA OF PHYTOPHTHORA snc etr. PLATE XL. A-C, P. Phaseoli grown in Lima bean agar. D-F, P. Phaseoli grown in same tube of oat agar with P. infestans. G-L, Hybrids produced by fertilizing P. hifcstciHS oogonia with antheridia of P. Phaseoli, p. 771. f\r\f*r\u\i r\r\CD r\c> c c AMTLJCDIHIA r\c D u \/Tr\ D UT u r\ D A ^ CONNECTICUT AGRICULTURAL EXPERIMENT STATION REPORT OF THE BOTANIST 1911 and 1912 G. P. CLINTON, Sc,a I. Notes on Plant Diseases of Connecticut, . 341 A. Diseases Prevalent in 1911 and 1912, T 341 B. Diseases or Hosts not Previously Reported, 344 II. Chestnut-Bark Disease, 359 ISSUED MAY, 1913 PART V. REPORT OF THE BOTANIST FOR 19H AND 19 12. G. P. CLINTON. I. NOTES ON PLANT DISEASES OF CONNECTICUT. A. DISEASES PREVALENT IN 19! I AND 1912. Weather Conditions in 1911. The winter of 1910-11 was rather open, with very little extremely cold weather. Snow was not abundant, and the little that fell did not cover the ground long. During January and February there were a number of rainy days. As this moist, warm weather was not followed by a sudden cold snap, comparatively little winter injury resulted. There were two late frosts during the first week of May that injured some of the fruit blossoms, especially cherry and certain varieties of apple, also tomatoes that had been set out early, but on the whole the injury was not extensive. In case of the apples, the pistils were frequently the only part of the blossoms hurt. Some of the very young leaves were also injured, causing them to have a stunted appearance, with the epidermis loosened, in a wrinkled irregular fashion, from the apparently thickened tissues beneath. The spring, on the whole, was rather dry and warm. Tune and July were extremely dry, with very hot periods in the latter month, causing an unusual scald of apples and, to a less extent, of peaches. Gooseberries were even baked on the bushes. This drought, perhaps the worst of those that have occurred during the last five years, was extremely hard on vege- tation in general, and especially so on certain market garden crops and on trees that had suffered previously from drought and winter injury. Hail during the summer caused some dam- age to tobacco and apples in certain restricted localities. From the middle of August on, the moisture was sufficient for most 24 342 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. plants, though it could not overcome the previous ill effects of the drought on some crops. An early frost, coming about September 13, cut the season rather short, and caused consider- able injury to corn and late tobacco. Diseases Prevalent in 1911. On account of the comparatively dry spring and very dry early summer, fungous diseases were not prominent, especially those that get their start in the spring. Among the more prominent may be mentioned the following: Sun Scorch, Sooty Blotch and* Speck Rots (due chiefly to Black Rot and Fruit Speck) of apple ; Scab of beets, prominent in the vicinity of Norfolk ; Leaf Spot of celery ; Black Knot of cherry and plum; Bark Disease of chestnuts, especially bad, apparently because of drought injury to the trees; Anthracnose of cucumber and muskmelon, and also Leaf Mold of the latter host; Leaf Scorch of hemlock, etc. ; Bacterial Blight of pear ; Tip Burn of potatoes ; Mildew of rose ; Calico and Pole Burn of tobacco. On the other hand, certain diseases were less conspicuous than usual, and in some cases not seen at all. Among these were: Rust and Scab of apple, less prominent than usual because of the comparatively dry spring ; Rust of asparagus, not uncommon at the end of the season, but late in starting, and so not especially injurious; Anthracnose of string beans, apparently quite incon- spicuous ; Mildew of Lima beans, not found at all ; Brown Rot, causing little injury to cherry and plum, and not so much as usual to peaches; Leaf Curl of peach, comparatively inconspic- uous ; Scab of pear, very much less than usual, even on suscep- tible varieties ; Late Blight of potatoes, entirely absent except in the northwestern part of the State, where it caused a little rot of the tubers ; Rust of quince, less prominent than usual. Weather Conditions in 1912. The year 1912 presented weather conditions rather different from those of the preceding year. In the first place, the winter was unusually severe, some of the coldest weather for years being recorded during January. As this followed much warm weather in December, it killed a good many fruit buds, particularly peaches, so that this crop was quite light, especially inland. This cold also produced some injury to the wood of peach trees, but not nearly so much as in some of the preceding severe winters. The spring was very wet in April and May, and as considerable rain had soaked into the ground during the winter, this largely PLANT DISEASES OF CONNECTICUT. 343 replenished the supply greatly depleted by the drought of 1911. This wet spring put back the earlier crops considerably, and late frosts about the middle of June added further to their troubles. These frosts injured garden crops considerably, and even killed the leaves of certain trees in the northern part of the State. The wet spring, however, favored forage crops as a whole. June and July (to the middle), however, showed another long drought period, but this was not so hot as that of the preceding year, and because of the supply of water in the ground, the deep- rooted crops did not suffer much. From the middle of July on, while some localities suffered from lack of rain, most of them had enough scattered rains to mature the crops in good shape, except potatoes, and, in some cases, onions. Another factor that made the season a favorable one for veger tation in general was the very late appearance of the fall frosts. While very slight frosts occurred the last of September and the first of October, these only partially killed the most tender plants, as melons, etc. The first heavy frost did not occur until Novem- ber 2, thus giving in the end an unusually long growing season despite the late spring. On the whole, the season was much more favorable to vegetation than the preceding one. Peach trees showed the best foliage conditions for some years. Diseases Prevalent in 1912. Fungous diseases were more prominent this year than the preceding, especially those that developed into prominence because of the wet spring. Among those occurring abundantly may be mentioned the following: Black Rot of apple, on the foliage, and Rust and Scab on the same host, especially the former, were abundant. The Cedar Apple, Gynnosporangium macropus, Plate XVIII c, which is the III stage from which the apple rust develops, was also unusually common in the spring, thus accounting for the abun- dance of the apple rust which followed later. Rust of white ash, Mcidium Fraxini, was also very common, being sent in for identification from a number of localities, especially along the shore. It was prominent there because the III, or mature stage, of this rust occurs on marsh grass, Spartina sps., which is common along the shore. The appearance of the I stage on the ash is shown in Plate XVII a. 344 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. Orange Rust of blackberry, etc., was more common than usual, as was also the Anthracnose of cherry. Sun Scorch and Black Spot of maple were not uncommon. The Bark Disease of chest- nut, on the other hand, seems to have been set back somewhat by the moisture conditions more favorable to its host, since a number of observers reported fewer infections, and old cankers with less vigorous development than in the preceding year. Bacterial Rot of cabbage did some damage in certain fields, and will be described later in this report.* Anthracnose of currants caused considerable .harm by premature defoliation. Leaf Spots of horse-chestnut and Boston ivy were more con- spicuous than usual. Leaf Mold of melons caused considerable injury, so that the sprayed vines did much better than those unsprayed. Leaf Curl of peach was more conspicuous by far than we have ever seen it, due to the favorable wet spring; and Scab was also conspicuous. Brown Rot, on the other hand, did comparatively little harm except to certain early varieties like the Champion. This was due in part to the light crop, and in part to the rather dry weather at harvest time. The Bac- terial Blight of pear and quince and the Rust of the latter host were more prevalent than usual, though not very serious. Early Blight of potatoes developed somewhat, and there was consider- able Tip Burn, but little or no Late Blight. There were a few complaints of Yellows of raspberry and Mildew of rose. Beside the preceding, there were reported during the two years a number of new or unusual troubles which we shall describe more in detail under the following heads : B. DISEASES OR HOSTS NOT PREVIOUSLY REPORTED. APPLE, Pyrus Mains. RUST, ORANGE, Rcestelia aurantiaca Pk. We have already reported two other species of rusts on the leaves and fruit of apple, but this is the first species we have seen occurring on the stems. This, however, is rather characteristic of the present species, as we have found it on other hosts, the quince and Cratsegus, not uncommon on the twigs. It was sent to the Station from two different localities during the past season, but evidently is not very common on the apple, as we have never col- lected it ourselves on this host. It forms fusiform swellings on PLANT DISEASES OF CONNECTICUT. 345 the twigs, and in these the fragile, white peridia, or fruiting cups, develop, and upon opening disclose a mass of bright orange- colored spores that by their color and microscopic characters are easily distinguished from the other two species previously reported. One of the specimens sent in the late fall showed the young twig swollen and still alive, while the fruiting pustules had not yet developed. This indicated that the twig might live over the winter and develop this stage the follow- ing spring. Ordinarily these swellings develop their fruiting bodies, and then are gradually killed by the fungus, so that the next season no further development occurs on them or on the uninjured portion of the twig below, thus showing that the fungus is not perennial on the host. The III, or Gymnosporan- gium, stage of the fungus occurs on both the red cedar and the common juniper in spring, and is spread from these to its alternate rosaceous hosts, among which, besides those already mentioned, is the Juneberry. BANANA, Musa sapientum. ANTHRACNOSE, Gloeosporiitm musarum Cke. & Mass. This fungus is not uncommonly found on bananas in our markets. It causes a blackening and dry decay of the skin. Eventually the fruiting stage shows as small, pinkish, more or less numerous exudations. If kept in a moist chamber, these become much more prominent. Cultures are easily obtained, and these pro- duce only the conidial stage. As these cultures differ somewhat in appearance from those of the bitter rot of apple, and never with us have developed any asco-stage, we believe Shear is cor- rect in considering it a distinct species. It is doubtful if Myxo- sporium Musae B. & C. (Grev. 3: 13), later issued by Ellis and Everhart (N. A. F. n. 2672) as Glceosporium Musae, is different, if we judge by the Ellis specimen, though the original descrip- tion gives the spores as somewhat smaller than in the species under consideration here. CABBAGE, Brassica oleracea. BLACK BACTERIAL ROT, Pseudomonas campestris (Pamm.) Smith. PI. XX a-b. This disease occurs on a number of related cruciferous plants, but we have reported it from this state before only on cauliflower. While we did not see it on cabbage until 346 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. last season, it seems quite probable that it has caused more or less harm to this host before, since it has been reported as quite injurious in several other Eastern states in times past. The trouble was called to our attention last year by a request, late in September, from H. B. Cornwall of Meriden to visit his farm and see what was the matter with his cabbages. Inspection showed that the trouble, which was quite serious, was this bac- terial disease. Although Mr. Cornwall had grown cabbage for some years, this was the first time that he had noticed trouble of this sort. From what we could learn from Mr. Cornwall, the disease apparently started in his cabbage from the seed of Danish Bald Head, which was imported. This variety was by far the most infected, and in looking over the old seedbed, we found several stunted seedlings of this variety that showed the disease. Mr. Cornwall also gave some of the young plants to several of his neighbors, and an examination of their fields showed the dis- ease on this variety, but not usually on the others. Mr. Cornwall did not notice the trouble until about the mid- dle of September, when, following a spell of muggy weather, this variety began to go down rapidly. Several other varieties, such as Copenhagen Market, Flat Dutch, and Savoy, showed little or none of the disease, although close to the Danish Bald Head. This probably means that the disease was not present in their seedlings, and that it spread to them later from the infected Danish Bald Head when the latter became badly infected. But of course it might also mean that these varieties were not so susceptible to the disease. The cabbage was on new land, and the plants were all from new seed beds. Part of the land had manure on it, and part had not, but this did not seem to make any difference. The Danish Bald Head first set out showed the trouble worse than those planted later. This disease is recognized by the blackened veins of the leaves, Plate XX b, where the bacteria develop chiefly, and in time extend down into the head. The leaf tissues finally turn yellow, and the leaves are easily pulled off. Soft rot, caused in part by other organisms, often loosens them at the base, and develops ari ill-smelling internal decay, XX a. The bacteria gain entrance through drops of water at the water pores on the margins of the leaves. PLANT DISEASES OF CONNECTICUT. 347 As the germs of this disease can be carried on the seed, as determined by Harding and Stewart, it is wise to see that the seed used does not come from a diseased crop. If doubt exists, it is well to treat the seed with formalin, 1-240, or corrosive sublimate, i-iooo, for fifteen minutes, as recommended by the investigators just mentioned. Likewise, if the disease shows up in a seedbed, this should be changed the next year. If bad in the field, this land should not be used for cruciferous crops for several seasons, and even if the disease is not present, yearly rotation is desirable where it can 'be carried on without especial difficulty. Refuse from diseased cabbages should never find its way to the manure pile. CURRANT, BLACK, Ribes nigrwn. PINE-CURRANT RUST, Cronartium ribicola Waldh. Plate XVII b-c. In our last report, 1909-10, p. 730, we noted the finding of a few specimens of the peridial stage of this fungus, known as Peridermium Strobi Kleb., on recently imported white pine seedlings in several plantations in the state. These pines all came from one firm in Germany. In April, 1912, Mr. Walden, while inspecting imported nursery stock in one of the nurseries of the state, found in a shipment of three-year-old white pine seedlings, purchased from Schaum and Van Tol of Oudenbosch, Holland, at least 185 that showed the character- istic swellings or fruiting stage of this blister rust (see illustra- tions). The whole shipment was destroyed in consequence of this finding. Since then the United States Government has placed a quarantine on the importation of white pines into this country from any of the European countries where this disease is known to exist. Since our inspection of the plantations previ- ously mentioned, no other examples of this rust have come to our attention, and, so far as we know, it does not exist to-day in this state. The II and III stages of this rust occur on species of the genus Ribes, which includes our currants and gooseberries. Although occasional outbreaks of the rust on currant had been reported at Geneva, N. Y., we had never found it in this state. In 1912 Stewart, of the Geneva, N. Y., Station, reported another of these outbreaks, and later Stone, of the Amherst Station, found 34-8 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. the disease in Massachusetts. The black currant seems to be by far the most susceptible of any of the varieties to this dis- ease. On learning of the outbreak at Geneva, we kept watch for this rust in Connecticut, and early in October received leaves of black currants from H. B. Birdsey of Meriden which showed the III stage of the fungus. These currants, originally obtained from outside the state, had been planted in his garden about eight years, but he had not noticed this trouble before, though it may have escaped his attention. This year he noticed it because of the premature defoliation of the currants. After locating this rust at Meriden, we visited several nurs- eries, and inspected their currants to see if it occurred there. We also wrote to all the nurseries in the state handling black cur- rants, and requested them to look for the disease on the fallen leaves, as it was, then late in the season, and to send us any suspicious ones. We were not able, ho.wever, to locate the rust in any of these nurseries. As black currants are not handled to any extent by our nurserymen, it is not likely that the dis- ease occurs with them. There are no white pines in the immediate vicinity of the rusted currants in Meriden, and Stewart has never found the peridial stage on the white pine at Geneva. This makes it look as if the rust might carry over on the currants in some way without the aid of this stage for reinfection in the spring. In connection with Stewart and Stone, we have started, in the greenhouse, black currants that were last year badly infected, to see if the rust will again appear on them without the aid of the peridial stage. These plants were brought into the green- house in February, 1913, and at this writing, April I5th, although in full leaf, they had as yet shown no signs of the rust. From this it appears as if the fungus did not (at least commonly) carry over on the currants. Possibly we have not learned all about the life history of this fungus. EVERGREENS, Various Species. DAMPENING-OFF, Rhizoctonia sp. During the past year complaints were received of dampening-off in coniferous seed- beds. At the Station trouble of this kind was also noticed, especially among the white pines. A superficial examination of these plants, which lop over on the ground and finally rot PLANT DISEASES OF CONNECTICUT. 349 off at the surface, showed no conspicuous growth of any fungus, but upon microscopic examination, especially after keeping the plants in a moist chamber, the characteristic myce- lium of this fungus could be found in more or less abundance. Cultures were readily obtained, and while these looked very similar to those of the potato Rhizoctonia, we are not sure whether they are identical. It seems, however, to be the same thing that causes dampening-off of a variety of plants in seed- beds and greenhouses. This same fungus was also found dampening off coniferous seedlings in the Elm City Nursery, especially those of the yew, Taxus cuspidata. Those in charge stated that it was almost impossible to grow seedlings of this species, as it seems to be particularly subject to this injury. They found that if, as soon as the trouble appeared, they sprayed the ground around the affected plants with Bordeaux mixture, and repeated the spray- ing when necessary, they could save a fair percentage of the seedlings. Sun Scorch. This may perhaps be considered a combination of winter injury and sun scorch. Various evergreens, especially hemlock, suffered severely from this widespread trouble in the early spring of 1911. While in most cases merely the leaves were killed in greater or less numbers, yet when this injury was severe enough the plants themselves died as a result of the severe defoliation that followed. Often only the outer ends of the leaves were killed, turning a reddish-brown in contrast with the green of the uninjured portion. The trouble was probably due to unusually warm weather in March and April, starting evaporation from the leaves while the roots were still frozen in the ground and unable, to readily replace this loss. Possibly part of the trouble may have been caused by the warm, moist weather in January and February and the subsequent colder weather. Plants recently re-planted suffered more than those well rooted. HOPS, Humulus japonicus. POWDERY MILDEW, Spharotheca Humuli (DC.) Burr. This fungus forms a whitish, powdery growth on the leaves and stems with a mature fruiting stage showing as very small, blackish, crowded specks, chiefly on the under side of the leaves. It was 350 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. found rather conspicuously in the fall on the variegated variety of the Japanese hop, cultivated for ornament in the writer's yard, and caused premature death of the foliage. While this mildew has been responsible for considerable damage in the hop districts of Europe in times past, it has only recently been com- plained of in the hop districts of New York State. Blodgett reports that dusting the plants with sulphur is a rather satis- factory method of controlling the trouble there. • JUKIPEB, CHINESE, Juniperus chinensis. RUST, Gymno sporangium japonicum Syd. Plate XVIII d. The last of March, 1911, Mr. Walden, while inspecting importa- tions from Japan at the Elm City Nursery, found on the above host, specially on the form known as compacta, an unusual rust on both stems and leaves. On a seedling of this same species, called /. virginalis, this same rust was also found, but only on the leaves. Altogether, 55 plants were found that had the out- breaks on the stems, and these were all destroyed. Those show- ing the rust only on the leaves were ordered planted in an isolated place, and an examination of them the next spring revealed no signs of the fungus. A few days after Mr. Walden found these infected specimens, he discovered others in an importation, also from Japan, of the Stephen Hoyt's Sons Nursery Company. In this case 49 plants showing the rust on the stems were destroyed. The writer determined both these col- lections to be the telial, or III, stage of Gymnosporangium japonicum Syd., which until this time had not been reported in America. An examination of Plate XVIII c-d shows that this rust is quite different from our common red cedar rust, though appar- ently it is not so different from some of the other species reported from this country, especially G. effusum. This fungus has been well described by Shirai in Zeitschr. fur Pflanzenk. 10, pp. 1-5, and he determined that the I stage is Rcestelia korecensis, which is more or less injurious to the foliage of pears ; and can also infect apples and quinces, in Japan. The gelatinous swellings of the fungus evidently developed on the infected trees in transit, though they appear in Japan a little earlier than in this country. These are the fruiting bodies, or sori, and are 3-5 mm. high, more or less flattened PLANT DISEASES OF CONNECTICUT: 351 or tongue-shaped, and run together on the stems, as shown in the illustration. On the leaves they are smaller, more isolated, more nearly conical, with one to three on a leaf. An examina- tion of the sori showed that they contained two types of spores, — one type long, pointed, thin- walled, chiefly in the interior of the sorus, and the other smaller, thicker-walled, with round apices, less abundant, and chiefly on the exterior. Those on the leaves are as a rule smaller than those on the stem. Shirai found that insects, especially bees, were important factors in carrying the sporidia of the germinating teleutospores in these sori to the alternate rosaceous hosts. This rust is probably perennial in the stems of the juniper, or else it takes two years for the sori to develop after infection. A juniper, which was badly rusted at the time of their discovery, was potted and placed in our greenhouse, where it has remained for two years. After the disappearance of the sori in the spring, the plant showed no signs of the rust that year or the next, but the spring following it again broke out in a different part of the stem, but not so conspicuously. Just how serious this rust might prove in its I stage on our pomaceous fruits; if it got started here, we do not know, but they certainly already have enough similar troubles. KAFFIR CORN, Sorghum vulgare var. GRAIN SMUT, Sphacelotheca Sorghi (Lk.) Clint. We have reported this smut before on sorghum and broom corn. In September, 1911, we found it not only on these hosts, but also on Red Kaffir corn grown at the Experiment Station farm for experimental purposes. None of these hosts are of commercial importance in this state, so the smut is not of economic import- ance here, though often serious elsewhere. It changes the seeds into kernels filled with a dusty mass of brownish-black spores. PEACH, Prunus Persica. STEM CANKER, Phoma Persica Sacc. This fungus has been reported previously in this country by Selby of Ohio (Ohio Exp. Stat. Bull. 92: 233. 1898. Ibid. 214: 423. 1910), who called it Constriction Disease of Stem, or Stem Blight. He reported it doing considerable injury in one lot of heeled-in nursery stock, 35 2 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. and he also found occasional specimens in orchards. Selby has not since found that this was a serious trouble in his state, and apparently the pruning off of the diseased branches is the only treatment necessary. From what we have seen of it in Con- necticut we do not consider it a disease likely to prove trouble- some here. Apparently it develops best on trees in a weakened condition. It was first found in Connecticut in October, 1911, by Dr. Britton, while inspecting one-year-old seedlings in one of the nurseries, and later the same nursery company sent the writer specimens, writing as follows: "We are sending you under separate cover some samples of peach twigs. These were sent us by a customer of ours in New York State. We think he planted these trees last spring, and he says that he has quite a few where the wood is black in the center and the foliage is turning yellow and the edges of the leaves have been looking bad since July i5th." An examination of both sets of specimens showed the fruiting stage of the Phoma fungus present. The twigs were partially or completely encircled by a depressed band of dead bark of varying width. This injury does not immediately kill the parts above, as the wood there often forms a greater growth than that below the cankers, giving rise to a slight swelling, though eventually the parts above are killed. The leaves turn yellow, and finally drop off. Cutting through the wood, we found a dark streak next the cambium, below the canker, but above it this was covered by the subsequent growth of the wood which formed the swelling. The stems were brittle and easily broken off at these areas. The fruiting pustules of the fungus show as small, more or less abundant, black specks. . From these there ooze out the hyaline, oblong to broadly oval spores, which are round at the ends, sometimes slightly curved, and 7-10 \i long by 3-3.5 /". wide. PINES, Finns sps. PINE- ? SOLIDAGO RUST, Peridermium delicatulum A. & K. Plate XVIII a-b. Late in June, 1912, while examining the leaves of Pinus rigida at Granby for Peridermium acicoluni, we not only found specimens of that rust, but also ran across specimens of another leaf rust on the same host, which was entirely dif- PLANT DISEASES OF CONNECTICUT. 353 ferent and had never been collected before in the state. This rust we determined to be Peridermium delicatulum, and Kern, to whom we sent specimens, verified our determination, and kindly sent specimens of the type for comparison. This rust was originally described in 1906 by Arthur and Kern (Bull. Torr. Bot. Club 33 : 412) from Florida on leaves of Pinus sp., and apparently had not been collected since. The illustration shows very well some of the macroscopic differences between this species and our more common Perider- mium acicolum. These differences are as follows: (i) The peridia of P. delicatulum are very inconspicuous, being deeply embedded in, and standing very slightly above, the leaf tissues, and open by a long slit; while those of P. acicolum stand up prominently, 1-3 mm. above the surface of the leaf, and fre- quently remain as white, tongue-shaped elevations after the spores are shed. (2) The fresh spore-masses of the first species are less dusty, and are crimson, as compared with the orange-colored sori of the other species. (3) Microscopically the spores are smaller (i 8-29/4 x 17-21^, subspherical or cuboidal to ovoid), and with minute verruculations, while the spores of P. acicolum are covered with coarse, scale-like tubercles. From observations made at the time, though not proved by inoculation experiments, it seems very probable that P. delicatu- lum has, like P. acicolum, its III stage as a Coleosporium on Solidago. Immediately under and close to the branch of Pinus rigida bearing the P. delicatulum was found a specimen of Solidago graminifolia var. Nuttallii containing the II stage of an undetermined Coleosporium. The spores of this were very similar in color and in fine verruculations to those of Perider- mium delicatulum on the pine, just as are those of the II stage of Coleosporium Solidaginis on Solidago rugosa similar in color and coarse tubercles to those of its peridial stage, P. acicolum. We have reported before that the spores of all the specimens on Solidago, etc., of the II stage of so-called Coleosporium Solidag- inis were not alike, and an examination of specimens on Solidago graminifolia var. Nuttallii already in the herbarium showed that these had the fine verruculations of this new species. It is hoped that we shall be able later by inoculation experiments to fully determine this species on the goldenrod and connect it with the suspected stage on pine. 354 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. PINE-SWEET FERN RUST, Peridermiwn pyriforme Pk. We have already reported this fungus (which has its II and III stages on sweet fern, known as Cronartium Comptoniae Arth.) on Pinus sylvestris, P. rigida, P. austriaca, and P. maritima, from the Station forestry plantation at Rainbow. In May, 1911, Forester Spring found it there on P. ponderosa, and in May, 1912, Forester Filley and the writer found it on this host and P. montana, both hosts new, at least to this state. This makes six different species of pine»on which we have now found this Peridermium. STEM CANKER, ? Phoma sp. Plate XIX a. Several times we have had young specimens of white pine brought to us by forest- ers showing the base encircled by a dead sunken area, as shown in the illustration. Occasionally we have found the Phoma fruit- ing slightly on these dead areas, and at least in one case, we obtained this fungus in cultures from the specimens. We are not sure as yet whether this fungus is responsible for the trouble or whether it merely follows winter and drought injury. Some of the specimens have the aspect of being quite parasitic. We have seen no notice of a Phoma canker of white pine in this country, but Tubeuf, in his Diseases of Plants, mentions two species of Phoma in Europe that attack the branches of various coniferous plants. One of these is Phoma pithya Sacc., and Saccardo, in his Host Index, gives the white pine as one of the hosts of this fungus. On the leaves of certain species of pine, including Pinus montana, we have seen Phoma acicola (Lev.) Sacc. It is a question with this species also whether it is parasitic or is merely following other injury where the leaves have been killed part way from the apex inward. QUINCE, Cydonia sps. FRUIT SPOT, Cylindrosporium Pomi Brooks. In our 1909-10 Report, page 723, we described the appearance of this fungus on the apple, and also reported finding it rarely on the common quince, Cydonia vulgaris. In October, 1912, the writer also found it on fruit of the Japan quince, Cydonia japonica. While the fruit of this was abundantly covered with small purplish discolorations, none of these showed the fruiting stage of the fungus. Cultures from the tissue, however, showed that they PLANT DISEASES OF CONNECTICUT. 355 were caused by this fungus. Of course the fruit of this orna- mental plant is of no economic importance. ROSE, Rosa sp. CROWN GALL, Bacterium tumefaciens Sm. & Towns. Plate XIX b. We have reported previously this bacterial disease on the following hosts: apple, bittersweet (Japanese), blackberry, peach, plum, and raspberry. Besides these, we have reported a somewhat similar trouble on the branches of oak trees, and a trouble of grapes which we have considered a winter injury, but which some others attribute to the crown gall organism. While the rose has been reported elsewhere as a host, it had not been found infected in Connecticut until Walden, in December, 1911, while inspecting Manetti stock recently imported from Eng- land by A. N. Pierson of Cromwell, discovered a few plants showing the galls conspicuously on the roots. Specimens of these have been planted in our greenhouse for over a year, and the disease does not seem to have as yet very seriously affected the plants, or to have spread to any extent to the new roots. TURNIP, SWEDE, Brassica campestris. PHOMA ROT, Phoma Napobrassica Rost. Plate XX c-d. In December, 1912, Mr. W. N. Durgy of Danbury noticed a rot trouble in his Swede turnips, and later sent specimens to the Sta- tion for information. Concerning this he wrote: "As I have a trouble with my Rock turnips this year that I never had before, I thought I would send you a sample. They were nice and solid when I put them in the cellar, and now nearly half of them are like the sample. Will you kindly report what is the cause of the trouble." Later, in answer to inquiries, he furnished the fol- lowing information: "The turnips did not show any spots when they were dug. The only thing we saw when we dug them was a decay on a very few around the top, so that when we pulled them, the top would come off, but I thought nothing of this. I have not heard of any similar trouble around here. I have made a specialty of raising turnips for a good many years, and have always stored them in the same place, i. e., the cellar bottom. My cellar is warm, but not very damp. I have had the farm for sixteen years, and never raised but one crop of turnips 356 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. before on the same ground, which was in 1911, but I manured it heavily with horse and cow manure, and used fertilizer besides." An examination of the turnips sent showed that they had a dry rot, appearing as sunken, subcircular areas scattered over the roots, especially above, as in illustration c. These areas usually had a darker border, but on the samples we received we did not notice that this was purplish or that the spots were finally cracked, as described for the trouble on Swedish turnips elsewhere. A microscopic examination showed the mycelium of the fungus abundant in these spots, and apparently the cause of the decay. No fruiting bodies showed, but after placing the turnip for a few days in a moist chamber, these became abundant, as shown in illustration d. Cultures of the fungus were easily obtained, and these produced a black growth in the medium with a scanty, superficial, whitish or slightly pinkish tinted growth above. The spores exuded more or less abundantly in rose- colored, viscid masses. Mr. Stoddard readily produced the dis- ease in healthy tubers, kept fairly moist and warm, on inoculation with spores from the cultures. The writer is indebted to Stewart of Geneva, N. Y., for several references to this disease in other countries, but neither Stewart, Selby, nor anyone else apparently, has reported a similar trouble in the United States. So far as the writer can judge from the meager description, our disease appears to be the same as that reported by Rostrup (5-6) from Denmark in 1893. He found it on Swede turnips, and describes as its cause a new fungus which he called Phoma Napobrassica. The trouble was next reported from the north of England, by Potter (4), who first noticed it in the winter of 1896-7. He also found it on the roots in the field. Potter merely identified the disease as caused by a species of Phoma, though he noted the possibility of its being the same species described by Rostrup. Carruthers (i) also reported this trouble from Lincolnshire, England, in 1903, and he had no doubt but that the disease reported by Potter and himself was the same as that described by Rostrup. In 1905, Kirk (3) reported the disease from New Zealand as new in that region. He gives the following description of the injury: "Below the crown,- and forming a kind of irregular ring around the upper third of the turnip, are numerous more or PLANT DISEASES OF CONNECTICUT. 357 less circular depressed areas of decaying tissue, varying consider- ably in size. They are light brown and corky, and are generally surrounded by a well-defined purple margin. As the disease advances, these patches crack and form deep fissures, which spread deeply into the interior of the turnip, ruining it. Numerous black dots (pycnidia) now appear on the diseased patches ; these dots are cone-shaped, and contain immense numbers of minute spores, which emerge from the apices of the fructification in small, globular, rose-colored masses. The spores then soon separate, and are disseminated by various agencies, especially wind." In 1912, Giissow (2) reported the disease from Prince Edward Island, Canada, and this seems to be the first report of the dis- ease from North America. While we have accepted Rostrup's name for the fungus, we are not sure whether it is distinct from a cabbage fungus (Phoma Brassiccz, or P. oleracea) that has caused more or less damage in Europe and was reported in 1911 by Manns (Ohio Agr. Exp. Stat. Bull. 228: 276-89) as causing serious injury in Ohio, especially through cankers on the stems. The cabbage and turnip both belong to the same genus, and so are closely related, and the Phoma fungi found on each cause cankers, and have spores about the same size. (Manns reports the spores of the cabbage Phoma as 4.5-5^ x 1.7-2/1,, while those of our turnip Phoma are chiefly 3. 6-4.5/11 x i.Sfi). But we do not know whether the spore masses of the cabbage Phoma are rose-colored, as are those of the turnip Phoma. Manns reports the fungus as occurring on the leaves somewhat, and McAlpine reports it on the leaves of cabbage, turnip and rape. Johnson has reported a Phoma disease on the leaves of Swede turnip in Ireland, and this may be the same as our Phoma. The other writers do not distinctly mention the Phoma as occurring on the leaves of turnips, though from the spraying treatment recommended, it is at least suggested that it may occur there. While the different investigators have suggested various pre- ventive treatments, it is not known yet whether all of these are practical, especially the spraying of the foliage in the field. Certainly, however, rotation should be practiced where the dis- ease has appeared in a field. It is also quite likely that the kind and amount of manure used in the field may have some influence. 35 8 CONNECTICUT EXPERIMENT STATION REPORT, This is especially true if diseased turnips have been fed to the stock. Storage in a dry, cool place, with piles not too large, may also help to keep down the trouble. No doubt the character of the season is a factor in the development of the disease. 1. Carruthers, W. Diseases of the turnip bulb. Journ. Roy. Agr. Soc. Eng. 64 : 297-300. 1903. [Illust.] 2. Giissow, H. T. Phoma rot of turnip. Exp. Farms Ottawa Rept. 1912 : 202-4. 1912. 3. Kirk, T. W. Diseases of Swede turnip. New Zealand Dept. Agr. Div. Biol. Hort. Bull. 14 : 1-4. 1905. [Illust.] 4. Potter, M. C. A new Phoma disease of the Swede. Journ. Bd. Agr. 6:(i-ii Reprint). [Illust.] 5. Rostrup, E. Oversigt over Sygdomme hos Kulturplanter. Tidsskr. Landokonom. 11:330. 1893. 6. Rostrup, E. Phoma-Angriff bei Wurzelgewachsen. Zeitschr. Pflanzenkr. 4 : 322-3. 1894. WISTAEIA, CHINESE, Wistaria chinensis. CROWN GALL, Bacterium tumefaciens Sm. & Towns. Although we do not find the above host among those mentioned by Smith as infected by the crown gall, yet so far as one can judge from macroscopic examination, it is occasionally infected in this state. Mr. Walden collected specimens in March, 1912, on plants imported from Japan in one of the nurseries, and Dr. Britton later brought us specimens from a plant grown in his yard. In the latter case the galls were associated with an elongated, sunken area of dead bark, and on this we found the fruiting pustules of a fungus that agrees fairly well with Phoma seposita Sacc. Whether the latter was present as a saprophyte or a parasite was not determined, but probably it was the former, since we have seen no references to it as causing injury. PLATE XVII I a. Ash Rust, p. 343. b. White Pine Rust, x 2, p. 347. c. White Pine Rust, nat. size, p. 347. SOME TREE RUSTS. PLATE XVIII ~a-b. Two species of Pine leaf Rusts, x 2-3, p. 352. c. Common Cedar Rust, p. 343. d. Japanese Juniper Rust, p. 350. SOME TREE RUSTS. PLATE XIX, a. Canker of White Pine, p. 354. b. Crown Gall on Roses, p. 355. DISEASES OF WHITE PINE AND ROSE, PLATE XX, a-b. Black Bacterial Rot of Cabbage, b. Showing blackened veins, p. 345. m. c-d. Phoma Rot of Swede Turnip, d, x 2, with fruiting pustules, p. 355. DISEASES OF CABBAGE AND TURNIP. CHESTNUT BARK DISEASE. 359 CHESTNUT BARK DISEASE, Endothia gyrosa var. parasitica (Murr.) Clint. HISTORICAL CONSIDERATION. Introduction. It is now over eight years since the chestnut blight was first found in New York, and nearly six years since it was reported to this Station as occurring in Connecticut. The writer became acquainted with the trouble in 1905 through Murrill's work and specimens sent by him, and has been actively engaged in a special study of it ever since its discovery in Connecticut. Articles (5-12) concerning these studies have appeared from time to time in the Station Reports and else- where. Since our views have been, in part, at variance with those held by certain other investigators, we propose to give here more in detail the information we have gained during these investigations, and our conclusions therefrom. We wish to acknowledge especial indebtedness to our assist- ant, Mr. Stoddard, who during the last three years has greatly aided in the work with artificial cultures, inoculation experi- ments, etc. Mr. Spring, the former, and Mr. Filley, the present, forester of this Station, have cooperated with the botanical department in determining the conditions in our for- ests and the possible remedial treatments. American and European botanists have aided with specimens and information ; and we are especially indebted to Professor Farlow, of Harvard, in our systematic study of the blight fungus and its allies. We are also indebted to numerous persons interested in forestry in Connecticut for much local information. Discovery of Disease. The chestnut blight was first noticed by H. W. Merkel, in charge of the trees of the New York Zoological Park, in the summer of 1904, as injuring scattered trees in that park. In 1905 it was so bad that he took active measures to bring it under control, and published (32) the first general description of the trouble in the Report of the New York Zoological Society for that year. The attention of Murrill, of the New York Botanical Garden, was called to the disease, which had now become quite conspicuous in the parks and woods in the vicinity of New York City, and he began a botanical study of it to determine the exact cause. 360 CONNECTICUT EXPERIMENT STATION REPORT, 1912. After a preliminary paper in the Journal of the New York Botanical Garden (45), published in June, 1906, he described in Torreya (47), in September of the same year, the specific fungus responsible for the trouble, a species new to science which he called Diaporthe parasitica. Previous to this outbreak there is no record, so far as the writer knows, of a disease of chestnuts in this country, or else- where, that can be surely attributed to the same cause, though there have been troubles of chestnuts in the Southern States that may or may not have been due to it. These will be discussed more fully later. Since the disease has been called to the attention of the public, however, there are a number of persons who have reported that they believe that they have seen this or a very similar trouble previous to 1904. For example, Metcalf and Collins (36, p. 45) say: "No earlier observation than this is recorded, but it is evident that the disease, which would of necessity have made slow advance at first, must have been in this general locality for a number of years in order to have gained such a foothold by 1904." And further on (p. 46) they add: "Observations by the junior writer indicate that this disease may have been present in an orchard in Bedford County, Va., as early as 1903, and that in Lancaster County, Pa., it was probably present as early as 1905." Dr. Britton of this Station informs the writer that as far back as 1889 he knew of a seedling chestnut tree on a farm near Keene, N. H., that suddenly, during the summer, developed a progressive canker trouble that now seems to him to have been the chestnut blight. Professor Davis, in the discussion at the Pennsylvania Chestnut Blight Conference at Harrisburg (54, p. 102), said: "I will say that I think I saw the blight on Long Island in 1897 or 1898. * * * That was in Cold Spring Harbor, in Huntington, especially back of Huntington, through the hills around there. So I think it was in 1898 well established in those localities." Mr. Child, of Putnam, Conn., at this same conference (54, p. 107) also said: "I know two men about sixty years of age who state that they are positive that they saw this blight twenty years ago, or something that looked the same as is shown in the blight to-day." CHESTNUT BARK DISEASE. 361 Early Investigations. We are indebted largely to Murrill (45-51) for our knowledge of the life history of the chestnut blight fungus. He not only gave a careful scientific descrip- tion of its different spore stages, but by inoculation experiments proved that it could produce the disease in healthy seedlings. He also tried various methods of control. The United States Department of Agriculture soon became interested in the disease, and through the efforts of Metcalf (33-39) and later of Collins (13-16) and others, facts concern- ing the distribution, hosts, and control of the fungus were made known. Metcalf (33) was the first to note the relative immunity of the Japanese varieties to the disease, and to sug- gest that the fungus was originally brought into this country from Japan. He is also, more than anyone else, to be credited for what good, if any, may arise from the attempted control of the fungus by the cutting-out quarantine method, since it is through his advocacy that this method has been undertaken in Pennsylvania and perhaps elsewhere. The writer apparently was the next after Murrill and Metcalf to take up the special study of the disease. He was the first to try to prove that weather had some connection with the trouble, and through his investigations, in connection with Farlow, to show the relationship of the fungus to two other species found in this country, all of which are now considered species of the genus Endothia. Recent Investigations. With the spread of the blight to new localities, and the appropriation of large sums of money by the National Government and the State of Pennsylvania for its special study and control, popular and scientific interest in this disease was greatly augmented. The more recent investigations have had to do largely with the detailed study of field conditions in the different states, especially in the State of Pennsylvania, where the force of scientific and general workers is larger than on any other special botanical investigation ever carried on in this country. This control work has been largely devised by Foresters Williams and Detwiler (19, p. 129), based on the cutting-out experiments of Metcalf at Washington (38). Recently Carleton, of the United States Department of Agriculture, has been given general control of all the work in 362 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. Pennsylvania, with Heald, formerly of Texas, in charge of the laboratory investigations. Collins (16) has contributed to our knowledge of the treat- ment of individual trees. Rankin (59, 60), of New York, has reported on results of inoculation tests as to time of year, water content of trees, etc. Fulton (24), of Pennsylvania, has made a variety of field observations as to distribution of spores, conditions of infection, etc. The Andersons (i, 2) have reported on the character of the fungus in cultures, inoculation tests, etc. Craighead (17) and others have studied its relation to insects. Miss Rumbold (62, 63) has experimented with chemicals to determine their effect on the trees as regards blight resistance, etc. Farlow (20, 21), Shear (64, 65), the Andersons (i, 2) and the writer (8-10) have studied the nomenclature and systematic relationships of the fungus. Stewart (70), Murrill (51, p. 194) and the writer have regarded unfavorably extensive control by cutting-out methods. Mickleborough (40, 41), Smith (67, 68) and others have contributed articles of interest to the general public. In Europe, von Hohnel (29), Rehm (61), and Pantanelli (52, 53) have published notes or papers on the subject. Identity. In the study of a disease it is always very desir- able to know exactly the fungus that causes it. While Murrill proved conclusively that his Diaporthe parasitica was the immediate cause of the chestnut blight, this did not necessarily prove, as he claimed, that it was a species new to science. The question naturally arises, has this fungus been previously known under some other name? As a vigorous parasite, killing off chestnut trees* there is certainly no record of any fungus that can be definitely identified with it. The writer from the first was skeptical about the fungus having entirely escaped previous observation by botanists, especially if it might under certain conditions exist as a weak parasite or a sapro- phyte. One of the first things we set about to learn, therefore, was whether or not this fungus had had a previous botanical record. Schweinitz, a Bavarian minister, who lived at Salem, N. C, and Bethlehem, Pa., and made his botanical studies from about 1812 to 1834, was one of the first and most extensive collectors of fungi in this country. He described many species CHESTNUT BARK DISEASE. 363 new to science. It was among the species described by him, since *the relationships of many of them are now somewhat obscure, that we made a search for some fungus that might throw additional light on Diaporthe parasitica. In this search we asked the aid of Professor Farlow, whose knowledge of American fungi is unsurpassed, and who has some of the Schweinitzian specimens in his herbarium, and from him we first learned of the close relationship of the chestnut blight to Endothia gyrosa (Schw.) Fr. This fungus was first described by Schweinitz as Sphaeria gyrosa, from North Carolina on Fagus and Juglans. He sent specimens to Fries, a famous authority on fungi in Europe, who later recognized it as a European species, and finally placed it under a new genus, Endothia. This possible relationship of the blight was brought out for the first time in the writer's Report (6) for 1908. Neither Farlow nor the writer had at that time examined the ascospore stage of the true Endothia gyrosa, so the exact relationship of our blight fungus to this species was not posi- tively determined, though the writer called attention to the fact that, so far as one could tell from the Cytospora stage, it was impossible to distinguish between Diaporthe parasitica collected on chestnut in America and Endothia gyrosa found on the same host in Italy. Previous to this, however, Rehm (61) had decided that Diaporthe was not the proper genus for our chestnut blight, and had placed it under the genus Valsonectria, but had not questioned its identity as a new species or its relationship to Endothia. Von Hohnel (29) seems to have been the first to definitely state that Diaporthe parasitica was not distinct morphologically from Endothia gyrosa, for in the latter part of 1909 he wrote: "Diese Pilz ist in Rehm Ascomyc., No. 1710, ausgegeben unter dem Nahmen Valsonectria parasitica (Murr.) Rehm. Es ist aber nicht anders als E. gyrosa mit schwach entwickelten Stroma." Since then Farlow (20), Shear (65), Saccardo, and Rehm, the last two in letters to the writer, have also decided that the chestnut blight fungus is not distinct morphologically from Endothia gyrosa (sometimes called E. radicalis) of Europe. 364 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. The Andersons (i) were among the last to study the rela- tionship of D lap or the parasitic a to the genus Endothia. Their studies having led them to believe that the blight fungus, though related, was entirely distinct from Endothia gyrosa, they have placed it under Endothia as E. parasitica (Murr.) Anders. Although the writer started out to prove the identity of the chestnut blight with the Endothia gyrosa of Europe, he has been forced to conclude from his microscopical, cultural and inoculation studies that it is ttot exactly identical with that species, as is held by von Hohnel and others. The relation- ship, however, is so close that he cannot, on the other hand, agree with the Andersons in considering it an entirely distinct species. Hence he (9) has placed it as a variety under that species, calling it Endothia gyrosa var. parasitica (Murr.) Clint. The preponderance of opinion of those who have made a critical study of the fungus, therefore, is that it is not an entirely new species, but that it is merely a strain, or at most, a variety of a previously described saprophytic or semi-parasitic species, that for certain reasons has now attained unusual viru- lence in the northeastern United States. CHARACTERISTICS OF THE DISEASE. As to the Host. It is easy enough to distinguish this disease on the smooth bark of sprouts or young trees, Plate XXIII a, since it forms definite cankers by killing the infected bark, and these usually increase in size until the entire stem or limb is girdled. These cankered spots are slightly sunken, and distinguished from the healthy bark by a chestnut-brown color, whereas the normal bark is more of a greenish-brown. Often the bark on these cankered spots is more or less cracked, and in time the fruiting pustules show as numerous minute cushions projecting through lenticel-like openings. On the rough bark of the older trees the cankers do not show very distinctly, though when cut out, as shown in Plate XXIII b, they give a cankered effect. Frequently with these the whole bark becomes infested, and the presence of the fungus is shown by the fruiting pustules breaking out from the deep cracks of the bark. Often when these do not develop, CHESTNUT BARK DISEASE. 365 the bark may look healthy, but when hit by a hammer, it gives a hollow sound and is easily separated from the wood, showing the cambium entirely dead. After the tissues are killed, one is apt to find the larvae of beetles, etc., at work between the bark and the wood, and their presence has led some to think that they were the real cause of the trouble. The first appearance of the disease on the smooth bark fre- quently seems to be due to the injuries caused by bark miners, Plate XXIV a. The most frequent starting points, however, are through cracks, wounds or where a branch has been pruned, XXIV b, or killed from some cause, as winter injury. Very frequently the fungus gets a start from a crack in the crotch of the limbs. In summer time the disease is recognized in the top of the trees, even at some distance, by the dead leaves on certain branches, which have been girdled, but whose girdled area is not easily seen from the ground, Plate XXII a. These dead leaves adhere for a long time to the branches. They first begin to show about the latter part of June or the first of July, when the previous year's canker has finally succeeded in girdling the branch. In the winter these dead branches some- times retain their dead foliage and burs long after those from healthy branches have fallen. This is true, however, of a branch killed prematurely from any cause. The cankers on the main trunk, as they become serious, cause the latent or adventitious buds in the healthy tissues beneath to develop, so that in time there are produced a number of slender sprouts, and one can detect the presence of a canker high up in the tree by these. The fungus, while it kills the bark and cambium, and thus eventually the tree, is not a true wood-destroying species. When the trunk of a living, but cankered, tree is cut and barked, the cankered spot, Plate XXIII d, is usually visible as a darker area in the wood corresponding to the cankered spot in the bark, the mycelium of the fungus having injured the woody tissues for a short distance inward. Such cankered spots can sometimes be seen on telephone poles used along the highway. This injury in itself, however, is negligible so far as it affects the value of the pole. 366 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. Often, after trees are cut, the stumps of those infected at the base develop a vigorous growth of the fruiting stage on the three or four outer rings of wood. This probably means that the mycelium can penetrate thus far into the wood from the canker, or possibly it may mean that fresh infection takes place from spores developing in the nutrient material furnished by the exposed sapwood. After an infected tree has been killed, or has been cut before death, there may be" a further development of the fruiting stage of the fungus. We doubt, however, if disease- free trees often develop prominent infection after cutting. In other words, the fungus is parasitic or semi-paraskic, but does not develop in its prime as a saprophyte. Even on trees killed suddenly and left standing, Plate XXII b, we have often failed to notice a general spread of the fungus through the bark. In the wood pile, too, while the fruiting stage no doubt shows some increase, a general subsequent infection of the disease-free bark does not seem to lake place. As to the Fungus. The mycelium of the fungus ramifies through the bark, beneath it, and often into the wood for a short distance. When the epidermis of a young, smooth, cankered branch is carefully peeled off, it often shows the mycelium as a whitish or yellowish coating just beneath, and below this is the reddish-brown diseased bark sharply marked off at its edges from the healthy white tissues.. In the older infected bark, the mycelium is sometimes seen as fan-shaped areas between the tissues or on the wood. The mycelium often gives a mottled effect to the bark as seen when cut through. In time, with the aid of insects, it produces soft, semi-dusty spots in the firmer, less affected tissues. The infected tissues do not show external signs of the fungus itself at first (with artificially inoculated cankers, not for two months or more after inoculation, Plate XXV b), but in the smooth bark in time numerous fruiting pustules are gradually protruded through small, lenticel-like openings. These at first are quite small, but in time show as subspherical to irregularly oblong cushions one-eighth of an inch or less in length and about that in height, XXIV c. In the rough bark they break out more irregularly from the crevices, and are more run together into compound groups, XXIV d. They vary in color CHESTNUT BARK DISEASE. 367 with age from light-orange through almost crimson- to dark chestnut-brown. The interior of the pustules is usually lighter colored, and more uniformly remains of a yellow tint. When fully matured, the fruiting pustules show small black dots on the surface or in cross-section, which are the ducts through which the matured spores escape. On the wood, the fruiting pustules are usually simple, smaller, conical in shape, and apparently do not produce the mature stage of the fungus. They have an appearance to the eye quite different from those on the bark, and for this reason Saccardo formed a distinct genus, Endothiella, for them. The pustules, within inconspicuous cavities, soon begin to form a summer, or conidial, stage. This, if it were the only stage produced, would place the fungus in the imperfect genus Cytospora, so this is sometimes known as the Cytospora stage of the fungus. The spores are produced apically in great numbers from slender fruiting threads. When filling the cavi- ties and swollen by moisture, they ooze out over the surface of the pustules as drops, or more frequently,, slender yellowish tendrils. These tendrils are most conspicuous in summer just after rainy weather. Soon, however, they become worn or washed away by rains, and, if carried to cracks in the bark, they cause new infection. As the spore masses are viscid and moist, they easily adhere to insects, especially when crawling over them in the larval stage, and to the feet and beaks of birds, and these are con- sidered means of spreading infection, not only in the neighbor- hood, but also to distant points. These spores, Plate XXVIII i, are very minute, in fact, so small that it would take two or three hundred million to cover an area an inch square. They are hyaline, oblong, unicellular with rounded ends, and about 2.5-4x0.75 p in size. In the same fruiting pustules that produce the Cytospora stage there appears, after some time, the mature spore stage, often called the winter stage, because it occurs most commonly from late fall to late spring. However, like the summer stage, this winter stage can be found more or less abundant at any time of the year, its appearance depending in part on the age of the fruiting pustules. With the beginning of this stage, the fruiting pustules have reached their maximum growth and the production 368 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. of the summer spores is practically over. It is quite unlike the Cytospora stage in that the spores are borne in sacs, or asci, situated in special receptacles called perithecia. The mature perithecia, Plate XXVIII k, are minute, light to dark-colored spherical bodies, situated within, but generally beneath and around, the edge of the pustules. By means of long black necks these perithecia open on the exposed surface of the fruiting pustules, where they show as minute black specks called ostioles. With trie later growth and wearing away of the fruiting pustules these ostioles sometimes project as short spines. Each perithecium contains numerous, hyaline, oblong, asci, Plate XXVIII f, tapering somewhat at their base, within which are eight ascospores arranged one above another in one or two rows. In size the asci usually vary from 40 to 45 /x in length by 7 to 9 /x wide, though some vary from 37 to 50 ^ in length. The ascospores, Plate XXVIII c, are hyaline, oblong to broadly oval, with a central septum, at which they are often slightly constricted. These spores are usually rounded at the ends, though sometimes somewhat pointed at one or both ends. They vary from 6 to 10 /* in length by 2.75 to 5 /*, in width. While the chief time of germination of the ascospores is undoubtedly in the spring, their production and germination seems to be more or less distributed throughout the year. After rainy weather they are shot through the ostioles of the perithecia with some little force, and no doubt may be carried much further by the wind. By this means their distribution is greatly facilitated, and, because of their greater vigor, some experi- menters believe they are more important in producing infection than the conidial spores. Progress of Disease. From our inoculation experiments it is evident that seedling trees one-half inch or less in diameter may be girdled, and in some cases their tops killed in one season, Plate XXV a. Sprouts an inch or more in diameter may likewise be entirely girdled for a distance of six or more inches, so that the death of the parts may be expected at least by the following spring. We have not inoculated the large limbs of trees, neither have we measured the rate of growth of cankers on the same, but we have had under general observation, for several seasons, marked trees at both Stamford and Middlebury. CHESTNUT BARK DISEASE. 369 From the results of these observations, it seems to take at least two, and more frequently three, four or more years, to entirely kill the larger trees. The trees at Stamford were on the farm of Mr. F. V. Stevens, and we are indebted to him and his son for aid in the experi- ments there. The trees were first marked by the writer and Mr. Filley in April, 1909. At that time many of them were in bad condition, as they were in the region where the blight first made its appearance in this state. All of the trees and sprouts in a certain area were numbered, and their condition as regards blight recorded. They varied in size from sprouts 2 to 8 inches in diameter to large trees two feet in diameter. The following table shows their condition when first examined, and after two growing seasons. They were not examined in 1911. In 1912, according to Mr. Stevens, Jr., all of the infected trees were dead ; some of the sprouts, especially those developed since the marking, however, were alive. In 1910 some of the dead sprouts did not show any, and others but little signs of the fungus, and their death may have been partly due to other causes, as drought and winter injury, though all are included in the following table. Sprouts, 2-8 in. diam. Trees, 10-24 'n- diam. Apr. 1909. Nov. 1910. Apr. 1909. Nov. 1910. No. % No. % No. % No. # Free 26 25.7 7 6.9 7 29.2 o o Little diseased 28 27.7 10 9.9 8 33.3 i 4.2 Moderately diseased ... 14 13.9 4 4.0 2 8.3 3 12.5 Badly diseased 24 23.8 15 14.8 2 8.3 10 41.7 Dead 9 8.9 65 64.4 5 20.8 10 41.7 Totals 101 101 24 24 The trees at Middlebury, all above six inches in diameter, were in a grove belonging to the Whittemore estate. For their experimental use the Station is indebted to the farm superintendent, Mr. W. M. Shepardson. The trees were on a hillside having a southern exposure, and had recently been thinned, by taking out those most diseased. They no doubt suffered from blight more severely because of winter and drought injury, due in part to their exposure and the thinning. The trees were first examined in February, 1910, and marked, but not numbered, with a sign indicating their condition as to 370 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. the disease at that time. They were examined again and re-marked at the end of that season, and examinations were made again at the end of the seasons in 1911 and 1912. In these later examinations data were not taken from all of the marked trees, but the condition of each tree examined was compared with its condition in the fall of 1910. The badly diseased and dead trees increased from 5.7 per cent, in the spring to 35 per cent, in the fall of 1910, to 58 per cent, in 1911, and to 69 per cent, in 1912. Th^ following table shows the conditions at the different times of examination : No. Not diseased 67 Little diseased 67 Medium diseased.. 14 Badly diseased.... 9 Dead o Totals 157 igio. Nov. 1910. Fall. 1910. Fall. I9II. Fall , 1910. Fall, 191 % No. % No. K No. f No. % No. Jf 42-7 0 0 24 20.5 O o 12 21.8 O 0 42.7 68 43.3 40 34.2 25 21.4 25 45-5 8 14 8.9 34 21.7 22 18.8 24 20.5 9 16.4 9 16 5.7 55 35-0 31 26.5 44 37.6 9 16.4 21 33 0 0 T CT 0 0 T T T 0 24 T TT 20.5 0 e e 0 17 e e 30 DISTRIBUTION AND HOSTS. In the United States. The blight, first noticed in the late summer of 1904 at Bronx Park, New York, was said by Merkel to have spread by the end of 1905 so that 98 per cent, of the trees in this borough were infected. Murrill (45), in June, 1906, reported the disease from New York, New Jersey, Mary- land and Virginia, and in September also from the District of Columbia. In February, 1908, he (48) gave Connecticut and Massachusetts as additional states. Metcalf and Collins (36) showed the distribution by August, 1909, to include Rhode Island, Pennsylvania and Delaware. Except in the vicinity of New York City, including adjacent parts of New York, Con- necticut, Long Island and New Jersey, the points of infection at this time, so far as known, were scattered rather than general. In May, 1910, Metcalf and Collins (37) included West Virginia among the infected states. The past year the disease has been reported also from New Hampshire and Vermont. At the present time the most damage caused by this disease in Massachusetts and Connecticut has been along and west of the Connecticut river. In New York it is conspicuous along the Hudson River up to Albany, and in western Long Island. CHESTNUT BARK DISEASE. 371 In New Jersey the chestnuts of the whole state have suffered. In Pennsylvania the trouble is serious in the eastern half, and quite bad in the southeastern part. The disease occurs gen- erally in Delaware, but is especially bad in the northern counties, where the chestnuts are most abundant. Maryland and Rhode Island have the disease scattered, and serious in certain localities. In Virginia and West Virginia the infections are apparently few and inconspicuous. In Connecticut. The first specimens from Connecticut were sent to the Experiment Station in November, 1907, by F. V. Stevens, Jr., of Stamford, who found the disease doing con- siderable damage in this region during the summer. He also mentioned that he thought he had seen it in one or two other towns in the state. Since that report others have stated to us that they had seen the disease earlier, but had not known its nature at the time. For example, Mr. G. H. Hollister, of Keney Park, Hartford, said that in the summer of 1905 he found a tree on the Edgewood Park estate at Greenwich that he is now sure had the blight. Forester Spring reported that a farmer in the town of Easton noticed the disease as early as 1905. These three towns are all in Fairfield County, near the first reported outbreak in New York. Hodson (28) reported the blight in New London County as early as 1908. Mr. N. J. Peck brought us a specimen from Woodbridge, New Haven County, in the winter of 1909, and reported that he had seen it in his woods for four or five years. The first fruiting specimen collected by the writer outside of Stamford was found at Morris Cove, New Haven County, in September, 1908, though immature specimens were seen that spring in Westville. By the end of 1908 the disease had been reported in all but one of the twenty-three towns of Fairfield County, in eight towns of New Haven County, and in one town of New London County. By March, 1911, the writer (7, p. 716) had reports of it in all of the twenty-three towns of Fairfield County, twenty-one in New Haven, fourteen in Litchfield, seven in Hart- ford, two in Middlesex, three in Tolland, and one each in Windham and New London counties. Out of these seventy- two towns all but seven were west of the Connecticut River. In November, 1911 (n), it was reported in 121 towns of the 37 2 CONNECTICUT EXPERIMENT STATION REPORT, 1912. state, and in February, 1912 (12), it had been found in 164 out of 168 towns of the state. Since that time it has been reported in the remaining four. We have no doubt that a careful examination would have revealed the blight's presence in many of these towns much earlier than it was first reported. There is no question, how- ever, that it was much more conspicuous in Fairfield and New Haven counties at first than elsewhere, and that to-day it is much more prevalent west than east of the Connecticut River. This is probably due to the fact that in the western part of the state chestnut is more abundant than in the eastern half, and also to the fact that the disease started earliest in the south- eastern part of the state. We doubt very much, however, if it has spread from a single infected locality in Fairfield County through all the rest of the state, but hold rather to the idea that it was present in a very inconspicuous way in a number of localities scattered over the state, and has spread from these. See Plate XXI. Manner of Distribution. Many persons believe that the chest- nut blight started at some one locality in the region of New York City and from there spread to all of the localities where it is now known to occur. Maps issued from time to time by Metcalf and Collins are based on this idea. Williams (54, p. 198) has rather positively stated this in the following quotation: "I would like to ask the gentlemen from around the neighborhood of New York City whether if they had been really active and alert and on the firing line when this thing was discovered in 1904, might they not have accomplished some real thing which would have redounded to the benefit of the other states, as Massachusetts has done in her gypsy moth fight? If instead of sitting down and nursing their hands in idleness, and allowing the scourge to go on, simply because they could not originate sufficient interest in their state, they had gone out and done what they could, this thing would probably not have come upon us." This view almost of necessity carries with it the additional belief that the chestnut blight is of foreign origin, since if of native origin there is little likelihood that the fungus would have been limited to one locality; whereas if imported, it could have spread from one center or even from a single tree. On CHESTNUT BARK DISEASE. 373 the other hand, the writer holds the view, at least tentatively, that the chestnut blight has not spread from a single central locality in New York City, but that at the time of its discovery there in 1904 it occurred in an inconspicuous way in widely scattered spots in several states, and that it has been in these localities for years. The reasons for this belief are as follows: (i) While origi- nally reported from the New York Zoological Park in 1904, sub- sequent information has shown that at about that time, or even earlier, in several cases already cited, the disease was present in such widely separated places as Woodbridge, Stamford and Greenwich, Conn. ; Huntington, L. I. ; Bronx Park, N. Y. ; Bergen County, N. J. ; Lancaster County, Pa., and Bedford County, Va. (2) Its sudden appearance and quick destruc- tion of the trees where first found (98 per cent, infected by end of 1905, as reported by Merkel) indicate that there was some other factor involved than the spread of a virulent para- sitic fungus, since such quick work is without parallel in the history of other fungous diseases of trees, or even with this one in its later history. (3) Recent investigations have shown that the fungus is more likely native than imported, and if native, there is no good reason why it should have been limited to the immediate vicinity of New York City. (4) Our investi- gations in Connecticut have shown it present in some localities in an inconspicuous way at the base of the trees, as if it were a native instead of an introduced fungus, just as its nearest relative is found to-day in the South. This latter fungus, Endothia gyrosa, is so generally distributed in the South that there is no doubt that it has occurred there since Schweinitz's time, and yet no one had, previous to our investigations, reported it on chestnut in that region. We believe that the chestnut blight fungus existed in the North previous to its outbreak in 1904 as a weak parasite in a number of scattered localities. From these centers it spread with greater or less rapidity according to local conditions. This belief does not in any way contradict the possibility of the disease being carried longer or shorter distances by such agencies as infected nursery stock, birds, etc. Perhaps the strongest evidence against this belief is the fact that the greatest damage has occurred in the vicinity of New York City, and 25 374 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. apparently has spread outward with the development of seem- ingly new infections. This apparent wave of progress, however, is in part due to a corresponding wave of interest on the part of the people to locate a disease so generally discussed. It is quite doubtful whether the disease was observed in most of the localities as soon as it made its appearance there, but rather our experience has been that it was usually discovered in a place when someone became interested enough to search for it. Hosts, Resistance, etc. While the blight was first found on our native chestnut, Castanea dentata, and most of the damage has been done to this species, it was soon determined that other species of Castanea were more or less susceptible to the disease. Murrill (48, p. 27) in 1908 called attention to these hosts, as follows: "It is now certain that the chestnut disease attacks all species of Castanea, both native and cultivated, that occur in this region, namely, Castanea dentata, the common native chestnut, C. crenata, the Japanese chestnut, and C. pumila, the chinquapin, found native from New Jersey to Florida." The European chestnut, Castanea sativa, though not mentioned by Murrill, is now known to be about as susceptible to the disease as our native species. At first certain varieties of this, as the Paragon, were thought to be more or less immune, but sub- sequent observation has not shown any that possessed marked resistance. Concerning the infection of the Japanese chestnut, Murrill said: "This discovery is especially timely because of the fact that the Japanese chestnut has been under observation else- where in the vicinity of affected native trees, and has been considered immune, so that it has been mentioned as a desirable substitute for the native tree in some of our parks." Metcalf also had noticed this apparent resistance of the Japanese chestnut, and published a short bulletin (33) in February, 1908, in which he says : "Observations made by the writer the past year indicate that all varieties and species of the genus Castanea are subject to the disease except the Japanese varieties (Castanea crenata Sieb. & Zucc.). All of the latter that have been observed in the field or tested by inoculation have been found immune. This fact can hardly fail to be of fundamental importance to the future of chestnut culture. Although the nuts are distinctly CHESTNUT BARK DISEASE. 375 inferior in flavor to the European varieties, such as Paragon, the Japanese is already grown on a large scale as a nut-pro- ducing tree. There are, however, many trade varieties of dubious origin. Some of these may prove later to be subject to the disease." So far as the writer has observed in Connecticut, the Japanese varieties seem to have more or less resistance to the disease, but our experience has not been very extended. We have seen two cases, one in a nursery and another in a private yard, where the Japanese species was directly attacked by the blight, but have examined it in nurseries several times with- out rinding any sign of the disease. We also failed to produce the disease in a Japanese variety in the Station yard, although the bark was inoculated in sixteen different places. In April, 1910, with the aid of the State Forester, we had set on the hillside, beside a badly diseased patch of chestnut timber on the Whittemore estate in Middlebury, six young trees each of the following varieties: Paragon, Reliance, Early Bon, Japan Mammoth, Late Tamba and Alpha, mostly Japanese varieties. These were planted to see if any would escape the blight. Unfortunately, many of them were killed back to the ground the first summer by drought. On the stems of some there appeared on the exposed southern side sun-scald cankers similar to those described by Powell, but no sign of the blight fungus showed that year. Since then a number of the trees have died from drought, but none have been killed or seriously injured by the blight fungus, though in 1911 a little of the fungus was found on two of the badly injured Japanese Mam- moth, and in 1912 on two of the languishing Paragon trees cankers had started. The Paragon, of all the varieties, stood the transplanting and drought conditions the best. Some years ago, through the work of the late Judge Coe of Meriden, Mr. Hale of Glastonbury, and Dr. Britton of this Station, considerable interest was aroused in the cultivation of chestnuts, especially the large fruiting varieties. While we know of no cultivated orchards that were set out, a number of men grafted these varieties onto the native sprouts and trees. Among these were W. O. Corning of Marbledale, and Mr. John Dickerman of Mount Carmel. Both these gentle- men say their grafted trees have been badly injured by the 376 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. blight Mr. Corning writes: "Of my Japanese trees a great many will have to be cut down. At the same ratio of progress, none will be left in three years." And in another letter he states further, in answer to our inquiry: "I bought in New Jersey cions for four kinds, namely, Japanese, Numbo, Ridgely and Paragon, all on chestnut sprouts. I bought at the same time trees from seedlings, but they all died before the blight struck us. I find the Japanese stand so far the best. The Paragon are the poorest, although the^ have made the best growth and produced the most chestnuts. I find the infection commences about at the juncture of the grafts on the sprouts, and runs up and down, faster up than down." Dr. Robert T. Morris, of Stamford, has experimented more with different varieties than anyone else in the state, so his statement, following a discussion of a paper by Collins (13, p. 43), is of special interest: "In my own orchards I have twenty-six kinds of chestnuts, and have followed them along for the purpose of determining which ones would resist the blight best. I cut out last year [1910] five thousand old American chestnut trees on my property. There is not a tree in all that part of Connecticut, the vicinity of Stamford, that is not blighted, and very few that are not dead. Now, in the midst of this disaster, what was the behavior of my experimental chestnuts of various kinds? It was this. I had about one thousand Coreans that lived up to five years of age, growing in the midst of blighted chestnuts, and none of these blighted. It occurred to me that it might be well to graft these on the stumps of American chestnuts, because these Coreans resisted the blight. But when I grafted them on the sprouts of American stumps, at least 50 per cent, of the Coreans blighted, showing that the pabulum wanted by the Diaporthe seemed to be fur- nished by the American chestnut. I had some chestnuts from North Japan that resisted the blight, and yet these grafted on sprouts from American chestnuts blighted. I had some Chinese chestnuts, and none of those have blighted as yet; and in grafting them, two or three have not been blighted. I have perhaps twenty-four chinquapins, both the Western form and the Eastern, and only one branch of one tree has blighted. Of the Southern Japanese chestnuts, very many are blighted. They are not as resistant as the Northern. I have a good many CHESTNUT BARK DISEASE. 377 chestnuts of European descent, and among these some resist the blight pretty well; and some of the American progeny, like the Hannum and Ridgely, seem to resist well enough, so that I am grafting these upon many different sprouts." As interest became aroused, inquiries have been frequently made if other trees than the chestnut, especially oaks, were not attacked by this fungus. For a long time its occurrence was not reported on any other host than Castanea. Even as late as April, 1912, Metcalf (35, p. 223) published the following: "So far as is now known, the bark disease is limited to the members of the genus Castanea. The American chestnut, the chinquapin, and the cultivated varieties of the European chest- nut, are all readily subject to the disease. Only the Japanese and some other East Asian varieties appear to have any resistance." Fulton seems to have been the first to report the chestnut blight on oak, having exhibited cultures in December, 1911, at the Washington meeting of the American Phytopathological Society. In his Harrisburg paper (24, p. 53) he reports finding a fungus on white and black oak in Pennsylvania, and says concerning it: "While it is desirable to carry on further cross inoculation experiments, it seems reasonable to suppose in the light of present evidence that Diaporthe parasitica may, under unusual circumstances, establish itself saprophytically on por- tions of trees outside the genus Castanea, if these portions are already dead. We have found no evidence that the fungus produces in any sense a disease of such trees as the oak." The writer and Mr. Filley first found the chestnut blight on oak in October, 1912, at Middlebury, Conn., in a badly diseased chestnut grove on the Whittemore estate. Previous search for several years had failed to show it on any of the various species of oak examined. At this place the fungus occurred rather inconspicuously, as follows : ( I ) On an exposed living root of Quercus alba that had been injured in some way; (2) On cut surface of wood of a live stump of Q. rubra from which young sprouts were growing; (3) On the dead bark and dead stub of a twig on a recently cut stump of Q. rubra. Also, in November of the same year, Mr. Walden, of the entomological department, brought to the writer specimens of white oak from Greenwich, Conn., that had been killed by drought, on which this fungus occurred. 378 CONNECTICUT EXPERIMENT STATION REPORT, Cultures have been made from all these specimens and from a specimen of black oak, Quercus velutina, sent by Detwiler from Pennsylvania, and all have shown the characteristic growth of the blight fungus as distinguished from Endothia gyrosa, which also grows on oak in the South. However, in none of the cases so far reported does the fungus seem to have been an aggressive parasite on oak. We doubt very much if it ever will produce any serious trouble, since the oaks are hardier than the chestnuts, and have not been deteriorated through sprout renewal. DAMAGE AND LOSS ALREADY CAUSED. Character of Damage. The injury caused by the blight fungus to the wood of the chestnut tree is not considered to be very important. Lumber, poles or ties cut from recently killed trees are not distinguished, as a rule, from those taken from perfectly healthy trees, and no data have yet been pro- duced to show that they are in any way inferior. This is because the fungus limits its attack to the bark, and the super- ficial layers of sapwood. After the death of the tree, the mycelium does not, apparently, form any progressive decay or deterioration of the wood. If the blight killed only the old trees ready for marketing the damage would not be very great. Loss arises in part from the irregularity of its attack. Each season some trees die, thereby making cutting and marketing inconvenient. The market is often glutted so that they cannot be disposed of to advantage. Further loss may arise in the deterioration of the dead trees if they are not cut soon after death, through decay started by other fungi and by insect depredations. The situation in Stamford, Conn., was shown in 1909 by Morris (42), as follows: "Millions of feet of fine chestnut timber, valuable for planking, piles, telegraph poles and cord- wood, will be lost within the next two years. Right now the blighted trees are still good for cutting purposes. I tried to dispose of about one thousand chestnut trees, but could not find a purchaser. All my neighbors are in the same predicament. 'No market/ is the regular reply to all my letters asking dealers if they handle wood of any sort. Forty or fifty cords of hard wood were rotting on the ground last autumn because I could CHESTNUT BARK DISEASE. 379 not find any one that wanted cordwood that had been split and stacked while clearing part of the property three years ago." The type of damage so far mentioned, however, is incon- spicuous in this state as compared with the loss that occurs through the death of trees which are not yet fit for commercial purposes and can be used only for cordwood. The market for the latter in certain districts is easily satisfied. This means low prices or long storage. The greatest loss is caused where future profits are entirely cut out by the death of half grown trees and sprout growth too small for present use. If the disease progresses in the future as actively as in the past, the prospects of our chestnut forests are very poor indeed. This means serious loss, for the chestnut is one of the most useful forest trees in all parts of the country where it occurs. Besides the loss from a commercial point of view, there is 'the damage caused to the shade and ornamental trees, and to groves kept on estates, parks, etc., for aesthetic rather than practical purposes. To estimate the damage here is impossible. In the United States. Certain writers have attempted to estimate in money value the loss caused by the blight. Just how this loss is estimated is not made very clear. To the writer it seems to be largely guess work. However, it is interesting to note these figures in order to compare them with losses given for other fungous diseases and insects. Murrill (49) in 1908 estimated the damage in and about New York City between five and ten million dollars. Mickleborough (40) about the same time estimated the damage through the country at not less than ten million dollars, while in 1909 he (41, p. 14) wrote: "The damage already done in the states of New York, Pennsylvania and New Jersey, would not be less than twelve million dollars." Metcalf and Collins (38) gave twenty-five million dollars as a conservative estimate of the financial loss to the country up to 1911. Detwiler (19, p. 130) estimates the loss in Pennsylvania alone as ten million dollars, allowing seven million for forest and three million for ornamental trees. The largest estimate that we have seen is that given by Marlatt (31, p. 345), who said in 1911: "It is estimated that the loss in and about the City of New York is now between five and ten million dollars, and the loss throughout the area now infested is fully one hundred million dollars." 380 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. In Connecticut. We shall not attempt to give any figures for the loss in Connecticut. To do this, one would have to determine the future value of sprout growth, and with more mature timber, to determine the difference between what one really got out of it and what he would have received if there had been no blight. Some idea of the loss, however, can be gained by an estimate of the chestnut in our forests and the percentage already injured by the blight. Hawes and Hawley, in their forest survey of Litchfield and New Haven counties, estimate the forest land in Litchfield as 55 per cent., and that in New Haven as 46 per cent., of their area. This gives a total of something over five hundred thousand acres of forest for these two counties. While considerable of this is in brush and some in white pine, by far the most of it is mixed hardwoods, with chestnut forming about 60 per cent, of these in Litchfield and 70 per cent, in New Haven County.- Counting in all the forest land, Litchfield probably would run over 45 per cent, chestnut and New Haven over 50 per cent., according to these authors. Probably no other county of the state has proportionately so large a part of its area in forest as Litchfield, according to State Forester Filley, but on the other hand, New London is probably the only one that has a less proportion than New Haven County. On the whole, it is perhaps safe to estimate 40 per cent, of all the forest land of the state as being chestnut. The census for 1910 gives the lumber cut of chestnut in this state for that year as 58,810,000 feet B. M., or nearly equal to that cut from all other trees. These statements show how extensive the tree is in our forests, and how useful. When we consider that from 5 to 90 per cent, of the chestnuts in different parts of the state have already been attacked by the blight, a clearer idea of the great loss already caused may be gained, especially in Fairfield County, where over large areas there is scarcely a chestnut tree to be found that is not either killed or infected by the blight. PRESENT SITUATION AND FUTURE PROSPECTS IN CONNECTICUT. In order to give some idea of the damage already done in different parts of the state, the botanical and forestry depart-- CHESTNUT BARK DISEASE. 381 ments of the Station, after consideration of all the data avail- able, have made approximate estimates of the percentage of chestnut trees attacked in each of the counties. To gain more immediate information as to the condition in the different counties, the writer recently sent the following letter to about seventy-five men scattered over the state who have been especi- ally interested in the blight and have had a chance to watch local conditions: "In 1911 the blight was more widely reported to us and was apparently more generally conspicuous than in any previous year. What we wish to learn from you is whether it was, where you observed it in 1912, more prominent, less prominent, or just about the same, as in 1911." Information gained by this and other means is given by counties as follows : Fairfield County. The blight was first found by Mr. Stevens, Jr., of Stamford in the summer of 1907, and reported soon afterward to the Station. From Mr. Hollister's observations at Greenwich, the disease no doubt occurred in the county at least as early as 1905. The injury has been greater here than in any other county, and is apparently now on the decline, since most of the trees have been attacked or killed. The Station estimates 75 to 85 per cent, of the trees already dead or infected. In answer to our letter, three report the blight worse, and four about the same or less conspicuous in 1912 than in 1911. Mr. F. A. Bartlett of Stamford writes: "The chestnut is practically extinct in Fairfield County." Mr. Joseph Cornwell of Norwalk says: "From my observations the chestnut blight was far more conspicuous in 1912 than in 1911. In 1912 I made a special trip into the woods for the purpose of exam- ining the undergrowth, and found it more affected by the disease than at any earlier period. My observations were made in Wilton, Norwalk, Westport, Ridgefield and Redding." Dr. R. T. Morris, who owns a farm near Stamford, says : "In the different years since the blight appeared some of my neighbors in the country have stated that they have observed more rapid progress than before, and others have expressed the opinion that we had less blight than before. As a matter of fact, so far as I can judge, there has been pretty steady progress of the blight from the first, and at the present time I do not know of a single unblighted tree in the vicinity of Stamford, Conn., although my men and I have taken long walks for the purpose 382 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. of finding a resistant tree in order to propagate this tree because of its individual characteristics. A great many thousand trees were examined." On the other hand, Mr. F. V. Stevens, Jr., of Stamford, writes: "I have found that in this section of the state the blight has been far less prominent than in any year since 1908 on the young sprouts, which are practically the only chestnuts we have." Mr. J. H. Treadwell of Danbury also says: "I would say that in this section dead trees caused by the attack of previous years were more in evidence in 1912 than in 1911. However, it does not appear to me that attacks on healthy trees are quite as prominent in 1912 as in 1911." New Haven County. This was the second county in the state in which the disease was reported. It was found by the writer in Westville in the spring of 1908. From the observations of Mr. Peck of Woodbridge, already alluded to, there is little doubt that it occurred in places here as early as 1905 or 1906. The damage has been second only to that in Fairfield County. Quite a little of the timber has been cut in recent years for use in brick kilns and brass foundries. This has resulted in con- siderable young growth, which is always likely to show the disease badly. In most of the forests many of the large trees have also been badly infected or entirely killed. We estimate that 55 to 65 per cent, of the chestnut has already been infected or killed. In answer to our letter, nine stated that they believed the blight was worse in 1912 than in 1911, while seven thought it about the same or even less conspicuous. Professor R. C. Hawley of the Yale Forest School, who has charge of the New Haven Water Company's forests, writes: "My observations have been principally confined to timber mer- chantable for cordwood or larger products. On such trees I think the chestnut blight has spread steadily in 1912 both in number of trees which it has attacked and, of course, in progress on trees already attacked. From a practical standpoint I antici- pate cutting out all the chestnut now merchantable in the vicinity of New Haven. My general impressions are that the disease is slowly spreading among the trees below cordwood size, although I have not devoted so much time to observing these trees." CHESTNUT BARK DISEASE. 383 Mr. W. M. Shepardson, of Middlebury, who has had con- siderable experience in cutting out diseased trees on the Whitte- more estate, says: "The blight was much worse in 1912 here than in any other year, and, as near as I can estimate, spread as much last year as in all previous years put together, so that in badly infested areas few or no trees are left without disease. In the home woods, round the fireplace and on the hill, where all trees were taken out last winter that we could discern, we found in September 845 trees over one foot in diameter that were much diseased and a great many smaller ones." Mr. G. H. Bartlett of North Guilf ord writes : "In the vicinity of North Guilford and North Madison the chestnut blight increased very rapidly in 1912. Young trees seemed to be less able to resist the attack than old and large ones. Present indications are that all chestnut sprouts will soon die. Some old trees seem likely to survive for a time." Mr. E. C. Warner, of North Haven, says, however: "In regard to the chestnut blight I would say it was very much more prominent in 1911 than in 1912. I think it spread very fast in 1910 and 1911, and not very much in 1912. In some places where we cut the diseased trees, blight did not increase very much, and one piece of sprouts I was through the other day did not seem any worse than last year." Mr. C. A. Metzger, of Mount Carmel, also writes: "As a whole, the blight seems about the same as last year. It does not seem to have advanced as fast as it has hitherto. On our Mount Carmel farm the number of trees infected this year seems less than the number last year." Litchfield County. Our first knowledge of the occurrence of the disease in this county was due to specimens sent by W. E. Frost from Bridgewater in January, 1909. The next August Mr. F. V. Stevens, Jr., sent specimens from Harwinton and also reported the disease from near Winsted; and Spaulding (69) found specimens at Bantam in September. In January, 1910, E. M. Stoddard collected specimens at Litchfield, and in March W. O. Corning sent others from Marbledale. So by the beginning of 1910 the disease was certainly well established throughout this county. So far the blight has not caused so much damage as in New Haven County, though in some places it has been very severe. Several of the best observers here seem 384 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. to have noticed an apparent halt in the progress of the disease the past year, which, if continued for another year, will give hope that the chestnuts may escape the severe injury caused in Fairfield County. We estimate the infected chestnuts to be from 40 to 50 per cent, in this county. Of the reports received, seven indicate an increase of the trouble over 1911, while six say the disease was about the same, or less con- spicuous. J. H. Putnam, of Litchfreld, writes: "I do not think that the chestnut blight has spread any worse the past season. Its ravages are more noticeable, as many trees previously attacked but not noticed, are now dead. The pieces where I cleaned it out two years ago do not show much spread since." In a later letter he adds this interesting statement: "We have no large trees killed, but have just cut a large tree seriously injured. The cankers on this showed that the disease had gained two to three inches in 1911, but only one-half to one inch in 1912, and in some places the new bark had held its own. Looking over a block of sprouts some ten years old, I found that where two years ago I had considered them doomed, they were making a splendid fight, and in some cases had apparently entirely over- come the disease." Donald J. Warner, of Salisbury, takes a similar favorable view, as follows: "I do not think that there were as many trees attacked by the blight in 1912 as in 1911 in this vicinity. On our own property in 1911 we cut several infected patches, and around these patches there were quite a number of trees which died in 1912. Of course it is quite possible that these trees had the disease in 1911 and were missed by the choppers. I did not notice nearly as many new cases as in the previous year." C. L. Gold, of West Cornwall, expresses the same view: "I have been cutting quite a lot of chestnut timber this last fall and winter, and find considerable evidence of the disease, which did not show much or at all before the tree was cut. However, the general appearance of our forests as we look at them from a distance showed but little signs of it the past season, nothing near as much as in the summer of 1911. It would seem as if the trees already infected would surely die, but from the results of the past season I am not so sure of it." CHESTNUT BARK DISEASE. 385 W. O. Corning, of Marbledale, however, reports a worse condition, as follows: "I sent two men this morning to cut out my next winter's wood, and I found a very bad condition, nine out of ten young trees about thirteen years old infected. I was on the same ground last winter, but I found only half as many diseased as to-day. Of my Japanese trees, a great many of them will have to be cut down, and with the same ratio of progress none will be left in three years." Ellicott D. Curtis, of Bantam, likewise sees no improvement, as he writes: "In our own woods the blight is much more conspicuous than last year, and is doing much greater damage. Some of the infested woods were thinned last winter, and the diseased wood taken out. This winter the disease is very prominent in these, and it looks as if the chestnut would have to be cut clean. It looks to me as if our chestnuts were com- pletely doomed, although I have not so far been able to find the disease in a small stand of trees about sixty years old." F. V. Stevens also takes a similar view: "At Torrington the outlook is about as bad as it was here [Stamford] three years ago, i. e., it promises to cause a total loss of all the chestnuts in that vicinity." Middlesex County. Forester Moss found a single infected tree in the state forest at Portland in March, 1910, and this is the earliest date we have for the disease in this county. Later examination, however, showed this infection to have occurred probably as early as 1906. The disease was seen by the writer at Middlefield and Middletown in March, and at Chatham and East Haddam in July, 1911. The blight as a whole is probably somewhat worse here than in Hartford County, but not so bad as in Litchfield. We estimate 30 to 40 per cent, of the chestnuts infected. Three persons report the disease worse, and three no worse, in 1912 than in 1911. Mr. J. E. Doane, of Centerbrook, writes: "I find plenty of blight in the chestnuts, more in the young than in the older growth. I find about one-half of the twenty-year-old trees in a tract that I have are either dead or diseased. I do not believe that there is any chestnut about here that has escaped from the blight, and think it has spread more in the last year than any time before." D. Herdman, of the Wadsworth estate of Middle- town, also thinks the trouble on the increase, as he says : "There 386 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. is no doubt in my mind but what the blight is more prominent on this estate in 1912 than it was in 1911." W. S. Hungerford, of East Haddam, reports an improvement : "I noticed the chestnut blight as being more conspicuous in 1911 with a slight decrease in 1912." Mr. J. C. Reeves, of Portland, says: "I think it showed up more prominently in 1912 in some localities, and not so much in others. On my land it was decidedly worse. Not so much new disease, but the trees showed it more. I think there is a change on the state land where we have cut it out. In some places where we would get a load last year, we did not find a tree with the disease." Hartford County. The first reports we had of the disease in this county were in the fall of 1910, Forester Filley having col- lected specimens at Hartland in September, and Spaulding (69) at Windsor, and L. H. Goodrich at Hartford, in October. In March, 1911, the writer found the disease at Granby. At present the disease is perhaps not as bad as in Middlesex County, though in some regions considerable damage has been caused. We estimate 25 to 35 per cent, of the chestnuts infected. Of the letters received from this county, three writers think the disease worse in 1912 than in 1911, and three think it was no worse. Mr. G. H. Hollister, superintendent of Keney Park, Hart- ford, writes: "As we made a pretty thorough cutting of the diseased chestnut trees last winter, I have not found the tops of the larger trees so badly infected as last year. I have found a great many trees with one or more branches infected, and more young trees than ever before. Probably many of the older trees have the blight, but it is not easily seen at present. On the whole, I consider the disease more prominent in 1912 than in 1911." S. W. Eddy, of Avon, says : "I looked over the woods yester- day, and would state that there is much more chestnut blight than last year. It showed up more in the young growth and small trees in the open. In fact, the woods and trees there show many leaves still holding on, and on looking them over, one can find the yellow or orange fruiting pustules." R. S. Tryon, of Glastonbury, writes : "The blight is generally prevalent here, I should say more prominent in 1912 than in 1911, but growth and spread appears not to have been so rapid. CHESTNUT BARK DISEASE. 387 Have noticed two or three instances where healthy growth appears to be overcoming diseased portions." F. H. Stadtmueller, of Newington, says: "We have as yet escaped any perceptible invasion of the chestnut blight in this immediate vicinity, consequently can make no comparative statements. Lumbermen of this neighborhood have reported it less prevalent in 1912 than in 1911." New London County. Hodson (28) in 1908 reported the blight along the Connecticut coast to New London, and about that time or a year later Hazard, a Yale forestry student, reported it present in North Stonington. The first specimens we received from this county were sent from Gales' Ferry by Dr. C. B. Graves in May, and from Lebanon by T. E. Clark, in October, 1911. The disease does not seem so bad in this county as in the preceding, and yet is worse than in the two following counties. We estimate the number of infected trees as between 15 and 25 per cent. Only three answers to our letters were received, of which two said the disease was worse in 1912 than in 1911, and one reported it about the same. Dr. C. B. Graves, of New London, writes: "I should say the blight was just about the same as to general prevalence, but it is my impression that the proportion of badly infected and dead trees may be somewhat greater." Walter C. Tanner, of Voluntown, says: "Where 1 noticed this blight in 1912, it was much more conspicuous than in 1911." Tolland County. The writer saw specimens of the blight at Mansfield in July, 1910; Filley collected specimens at Bolton in November of the same year; and H. Wood sent specimens from Tolland in April, 1911. As yet the blight has done com- paratively little harm in this county, less than in any other except perhaps Windham. We estimate the percentage of infected trees to be between 10 and 15 per cent. Of the replies received to our letter four place the disease as more, and three as the same, or less conspicuous in 1912 than in 1911. E. G. Walker, of Union, writes : "There is very little chest- nut blight in Union, and I do not think there was any increase over 1911." George Towne, also of Union, says, however: "More cases of the chestnut blight were observed by me in 1912 than in 1911. There is little doubt that it is spreading in this locality." Harry Wood, of Rockville, also thinks it on the 388 CONNECTICUT EXPERIMENT STATION REPORT, 1912. increase: "In answer to your question it is my opinion that the disease around here has steadily increased in the past two years." George V. Smith, of Willington, says : "The blight is increas- ing quite rapidly in this town. In 1911 I did not observe more than a few cases. In 1912 I found it in colonies of infection. Some men tell me they are finding it everywhere in chestnut cuttings. Two years ago I did not find a tree on my farms. Now there are many." Professor C. D. Jarvis, of Storrs, writes, however: "Replying. to your letter, I would say that in my opinion the chestnut bark disease has not been so con- spicuous during the past year. Fewer new infections were discovered, and the spread of the disease seems to have been much slower in the sections where it was present." Windham County. Former Forester Spring collected the first specimens we had from this county at Windham in September, 1910, while Filley and Stoddard reported it from several towns in the fall of 1911. The last two towns in the state in which we found the blight were in this county. The situation here is about the same as in Tolland County, or perhaps somewhat better, as we estimate only 5 to 10 per cent, of the trees infected. Two reported the disease worse, and four as the same or better in 1912 than in 1911. Mr. W. H. Hammond, of Hampton, writes: "So far as my observation went on my own farm, I was of the opinion that the blight did not spread last year as much as I expected, but there were many reports of it in new sections of the surround- ing towns." C. S. Hyde, of Canterbury, says: "I should say the blight was about the same as in 1911, but if anything not quite so prominent in this section." C. E. Child, of Putnam, says: "Less prominent in 1912." On the other hand, C. A. Tillinghast, of Danielson, writes: "I have found the chestnut blight spreading quite rapidly in this section, much more in 1912 than in 1911." Future Outlook in the State. If we judge from what the blight has already accomplished in Fairfield and New Haven counties, and what it is now doing in certain parts of Litchfield, Middlesex and Hartford counties, there does not seem to be much hope for those regions where the blight has become firmly established. There are those who believe that the blight is bound to go on in the future just as it has in the past, which CHESTNUT BARK DISEASE. 389 means the death of all the chestnuts in the infected regions. On the other hand, there are others, like the writer, who believe that there have been unusual conditions that have favored the rise and spread of the disease so far, and that the crest of this wave of infection is bound to be reached, and a gradual decrease to follow when these conditions are changed. The blight has become far too prevalent and widespread to show sudden improvement in a single year, yet we believe that a let-up in its destructive spread was shown in the year 1912. In 1911, according to all our information, blight was by far more conspicuous and became more widely distributed than in any previous year. This was a year of serious drought, follow- ing several dry years. In the winter and spring of 1912 numerous rains replenished very largely the depleted supply of water in the soil, so that even trees in general that had not suffered seriously from any particular trouble showed decided improvement in foliage and growth. This was especially true of the peach, which is a very good indicator of weather con- ditions. True, there was a drought period in midsummer in 1912, but this did not affect trees so much as it did the super- ficially rooted crops. Now, if weather conditions have had nothing whatever to do with the spread of blight, so far as increased or decreased vigor of the chestnut trees is concerned, then the blight in 1912 should have been far more prominent, destructive, and widespread than in any previous year. Yet, thirty-one out of sixty-four persons answering our letter stated that the blight was no worse, or even apparently better, in 1912 than in 1911. If our observations and those of the persons who corroborate them are true, then there is certainly some hope for the future of the chestnut in Connecticut. Just what percentage of the trees will survive the blight. we do not aim to predict, but we certainly do not believe they are all to be exterminated. RELATION TO CONDITION OF HOST. General Statement. Some writers believe that the condition of the host has had no influence whatever on the rise and spread of this disease. For instance, Metcalf and Collins (37) in 1910 said: "A debilitated tree is no more subject to attack than a 39° CONNECTICUT EXPERIMENT STATION REPORT, 1912. healthy one. * * * Dry weather checks the disease by sup- pressing spore production. * * * Winter injury is not common over the whole range of the bark disease, but may be locally important in producing lesions through which the parasite enters. Winter injury bears no other relation to the bark disease." Metcalf (35, p. 225) in 1912 said again: "No definite evidence, experimental or otherwise, has been adduced to show that a tree with reduced vitality is more susceptible to infec- tion, or that the disease spreads more rapidly in such a tree than in a perfectly healthy and well nourished tree of either seedling or coppice growth, provided that such reduced vitality does not result in or is not accompanied by bark injury by which spores may gain entrance." Now, if the condition of the host bears no relation to the rise and spread of the disease, the writer knows of no satis- factory explanation for its sudden and destructive appearance in this country except its importation from some foreign country. The evidence to date, however, is very strongly against the idea that it is an imported pest, as we shall show later. Among the farmers in Connecticut who have been able to watch this disease rather closely there are many who believe that the weakened vitality of the chestnuts has had considerable to do with its development and spread in this state. The writer more than anyone else has advocated this view, and we propose to give here the reasons we have for holding it. Briefly expressed, they are as follows: The chestnut blight was brought to sudden prominence just after the severe winter of 1903-04, which injured and killed fruit and forest trees in general along the coast and water- courses, of which New York City was the central point. The resulting enfeebled condition of the chestnut enabled the blight, a previously inconspicuous parasite, to spring into sudden prominence on these trees and to gain credit for the death of others which had been largely or entirely due to winter injury. Since then we have had one or two severe winters, and more especially several dry summers, that have injured not only the chestnut, but other forest trees over an extended area. Due to its successful attack on the weakened trees, the blight fungus has perhaps acquired an added virulence that has enabled it to attack apparently healthy trees, especially those of sprout CHESTNUT BARK DISEASE. 391 renewal. The enfeebled condition of the chestnut trees and their consequent susceptibility to the blight may possibly be related to some lessened chemical activity in the bark and newly- formed wood, such as the production of tannic acid, for instance. If so, then when this has returned to its normal production through favorable weather conditions, the blight should gradu- ally become correspondingly less aggressive. Under the follow- ing heads we shall take up more in detail our ideas of the relationship between weakened vitality of the chestnut and consequent susceptibility to the blight. Winter Injury. We have in a previous Station Report (6) called attention to the results of winter injury on fruit and other trees in Connecticut. We shall attempt here to show also that these conditions were not confined to this state. In Decem- ber, 1902, following a very open fall, the temperature suddenly fell below zero, with the result that many trees, especially young fruit trees which had not properly matured their wood, were severely injured or killed outright. The following winter of 1903-04 was so unusually severe that thousands of fruit trees in Connecticut, especially those situated in the valleys and on the lower slopes, were killed, and others so severely injured as to develop physiological troubles for some time afterward. The injuries caused by these two winters were most noticeable in the region along the Sound, in the valleys or on the lower hill slopes, and along the river courses, regions in which the chestnut blight afterward first appeared, and in which it has caused the most damage. The winters of 1906-07 and 1907-08 also caused considerable winter injury. Although we did not at the time directly study the effect on the forest trees of these winters, especially that of 1903-04, which was the most severe, we do know from subsequent observations that many trees were injured. In the summer of 1904 we examined a young fruit orchard, at Stamford, whose wood had been largely killed by winter injury; and two or three years later in examining chestnuts from this region, where the blight has been the most severe, we could see indi- cations of winter injury to the wood of the chestnut sprouts dating back to the winter of 1903-04. In the winter of 1910, in examining chestnut at Middlebury, where the blight was just coming into prominence, we found quite a number of 392 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. injured and dead trees with no sign of the blight on them. There were others with the bark killed on the south or south- west exposures, and sound on the northern, as shown in Plate XXIII c by the dark and white wood ; and on many of these there were no signs of the blight fungus as yet. There is no doubt that these trees had been injured by an attack of sun- scorch winter-injury, complicated probably by summer droughts. That we are not alone in believing that these winters did not confine their injurious effects to Connecticut or to fruit trees, that they may have had some connection with the chestnut blight, and that some persons have attributed their effects to fungous and bacterial troubles in certain cases, we shall attempt to show by the following quotations. Concerning the injury to fruit trees caused by the severe winter of 1903-04, Waite, of the United States Bureau of Plant Industry (Bull. 51), writes: "The severe cold weather of the past winter, especially the intense cold of January 4th and 5th, resulted in very severe damage by freezing to orchards in New York and New England, especially in the Hudson and Con- necticut valleys. The damage was found to be mainly to peach, Japanese plums and pear trees, and the most serious harm was largely confined to the lower levels and pockets." Eustace, of the Geneva, N. Y., Station (Bull. 269), in his discussion of this winter injury, says: "The winter of 1903-04 was an unusually severe one throughout New York state. In many places the temperature was the lowest on record, and the periods of extreme cold were protracted. As a result the end of the winter found many of the orchards, especially those of peaches and pears, extensively and seriously injured. * * * The damage was greatest in the Hudson River valley, where the cold was most severe, more than forty degrees below zero being reported. * * * At the end of the winter the external appearance of the trees was entirely normal, the bark of the trunk was smooth and of normal color, and the twigs on all parts of the tree were plump and bright. Nothing about the trees looked unusual or wrong, but upon cutting into the trunk anywhere above the snow line, it was found that both bark and wood were discolored for some depth into the trunk. * * * Altitude, air drainage, and con- dition of the soil had a very important bearing upon the severity of the injury. The advantages of a high altitude were best CHESTNUT BARK DISEASE. 393 shown in some of the peach orchards in the Hudson Valley. * * * The dying of the trees (afterwards) at such unusual and irregular times gave rise to much alarm among the fruit growers in some localities. It was feared that a virulent attack of the yellows had broken out, or some new and serious disease had become prevalent." Whetzel, of the Cornell, N. Y., Station (Bull. 236, p. 133), says concerning a supposed outbreak of the bacterial blight of apple in that state: "Anything that reduces the general vitality of the tree tends to render it more susceptible to attack of the bacteria. I have already referred to the apparent effect of low temperature in relation to this disease in the Hudson River region. A long growing season during 1902, with exces- sive rain, followed by a sudden and extreme fall of temperature early in December, is referred to by growers in that section as the beginning of the injury to their orchards. The winter that followed was a severe one, with sudden and severe changes of temperature during the early days of the spring of 1903. Many trees failed to leaf out, and large cankers were now observed on limbs and bodies of dead and dying trees. The general conclusion at once prevailed that these dead spots were the direct results of these weather conditions. * * * I am there- fore of the opinion that many of the trees in the Hudson River Valley and about Kirkville were cankered prior to the winter of 1902-03. The severe weather no doubt weakened the trees yet free from the disease, thus rendering them more susceptible to attack during the summer of 1903. * * * The winter of 1903-04 was also a severe one, and no doubt added to the sum of the injury already produced. To just what extent the winter injury in this section is responsible for the death of the trees is a question. In certain cases it was very evident that the trees had died from this cause." This statement shows that Whetzel recognized the importance of these winter injuries, though apparently he made a mistake in considering blight the major cause of the trouble. Stone, of the Massachusetts Station (Report 20, p. 123), also says: "In previous reports attention has been called to some of these troubles, more particularly to the extensive winter killing which caused so much injury during the winter of 1903-04, at which time thousands of trees and shrubs were 394 CONNECTICUT EXPERIMENT STATION REPORT, severely affected, many having been dying slowly ever since. Besides the trees which are dying, there are many others which are in a very much weakened condition. Numerous oaks which were injured four years ago have died during the past three years, and some of these not yet dead are gradually becoming weaker. * * * Mention has previously been made in our reports of the condition of the red maples, many of which are now gradually dying, and the white and rock maples are suf- fering to a limited extent from the same cause." And in a later Report (23, p. 66) he adds : "The severe winter of 1903-04 was not confined to our state, as its work may be seen through- out the whole northeastern section of the United States, and in many instances large orchards were wiped out entirely." The so-called pine blight was a trouble very prominent in New England a few years ago, culminating in its damage in 1907. At first some investigators, as well as growers, tried to show that this was a fungous trouble, but the investigations of Stone of Massachusetts, Morse of Maine, and of the writer, proved that it was entirely due to unusual seasonal conditions, prominent among which was winter injury. Concerning this trouble, Stone (Report 22, p. 65) writes: "The present pine blight dates back to the winter of 1902-03, when the conditions were such as to cause much injury to vegetation in general. The following winter, 1903-04, was even more severe in its effects on vegetation, and caused extensive root killing of many trees and shrubs. Pine, as well as other trees, in many cases was killed outright, but the injury to the pine was largely con- fined to the small roots or those less than three-sixteenths of an inch in diameter." Morse (Forester's Seventh Rept, Me., p. 24) also says: "Practically all of the so-called pine blight in Maine appeared in 1907 and 1908, and was coincident with tl|e most destructive winter injury to fruit trees known in the state in the last hundred years." In the spring of 1907 a late frost killed the immature leaves of the sycamore over a considerable area, as shown by von Schrenk and the writer. It is at this time of the year that the anthracnose fungus begins to be prominent, and the action of the frost was so similar to that of the fungus that several investigators, who apparently were not acquainted with the result of this frost, later laid the trouble entirely to the fungus. CHESTNUT BARK DISEASE. 395 And this has been the case with a number of investigators who have laid winter-injury troubles largely or entirely to the fungi which later became prominent on the winter-injured tissues. One of the first problems the writer had in Connecticut was to connect, as the cause, a Cytospora fungus found on cankered bark of apple trees. We did not know as much about winter injury then as now, and were using the agent that was most evident at the time of the investigation, which occurred some time after the winter-injured cankers were produced. As to the relationship of winter injury to the chestnuts themselves, we have this statement by Murrill (45, p. 153), when he first began his investigations: "It is possible that the con- spicuous ravages of the disease about New York City are largely due to the severe and prolonged winter of 1903-04, in which many trees of various kinds were killed or injured." Later, Murrill seemed to have given up this idea. Stone (Report 23» P- 57) a^so writes on this point: "The writer has been informed by one who has had some opportunity to observe this disease, that it appears to be less prevalent on high eleva- tions than in the valleys. * * * It is, however, quite significant that the Connecticut Valley region should possess such a large amount of infection as compared with other sections. We have noticed for some time that there is a difference in the degree of winter killing occurring in valleys and high elevations in this state. By far a greater amount of winter killing of trees occurred in river valleys and on the lower elevations, the Con- necticut Valley being especially notable in this respect. It is, moreover, a significant coincidence that the chestnut disease should make its appearance at about the same time that vegeta- tion was so severely injured by the severe cold which occurred during the winter of 1903-04 all over the northeastern part of the United States." From the preceding discussion we have made it evident that there was a general and severe injury of trees of various kinds, resulting especially from the winters of 1902-03 and 1903-04 in New England and New York. We believe that the same conditions would have been found true for at least New Jersey and eastern Pennsylvania, had observations been made there at that time. This winter injury took severest effect along the 39^ CONNECTICUT EXPERIMENT STATION REPORT, IQI2. Sound* and its contributory rivers, and was soon followed in all these regions by the outbreak of chestnut blight. Merkel (32), just about a year after the blight was first noticed by him, states that 98 per cent, of the trees were then affected, and adds: "The disease was noticed with equal frequency upon young specimens in the nursery, upon sprouts that had sprung from stumps of trees cut down the previous year, on young vigorous trees thirty to forty feet high standing in deep, rich soil, and also upon the • few survivors of the primeval forest with trunks twelve to fourteen feet in circumference." Such a destructive and indiscriminate attack in a single year is not the history of the blight in the later infected regions. To the writer it leads to but one conclusion, namely, that in those regions where the blight first appeared and was most severe the trees had suffered severely from winter injury, as this is the only agent we know of that acts in such a quick and thorough manner. Drought Injury. There are a number of observers, like Met- calf and Collins, who claim that lack of moisture as affecting the vigor of the chestnut has nothing whatever to do with the spread of the blight, but that, on the other hand, it should show greater progress in moist seasons, since these favor spore development and infection. This idea is also expressed in the following statement by Murrill (46) : "Dry summers and otherwise unfavorable conditions may delay the progress of the disease a few years, but not very long." If the fungus were a strictly parasitic species, the condition of whose host made no difference in its virulence, this would be true. The writer, however, holds that the reverse is really the truth, namely, that drought, by weakening the trees, has greatly increased the spread of the disease, and that moist years, while favoring spore production, increase the resistance of the trees, and thereby really lessen infection. From 1907 to 1911 Connecticut, at4 least, had an unusual series of summers, with drought periods that caused serious damage to cultivated crops and forest trees in general. For trees alone, that of 1911 caused the most injury, since it was not only severe * Hodson (28) wrote in 1908 :— "A favorable feature in the situation is that so far the disease has done most damage in the vicinity of the sea." CHESTNUT BARK DISEASE. 397 in itself, but was a culmination of a period of dry summers. During this dry period blight has been most conspicuous in its development and spread in Connecticut, culminating in 1911 with by far the most frequent complaints of damage and spread to new localities. Its unusual prominence in 1911 was not con- fined to Connecticut, for according to Rane (57, p. 49), Met- calf wrote him: "During the past summer the disease has spread more than in all its previous history." As we have already stated, the winter and spring of 1912 were so wet that much of the depleted moisture was restored to the soil. As the result, the general aspect of fruit and forest trees, including chestnut, showed great improvement over 1911, and along with this came a more or less apparent let-up in the spread and severity of the blight. The particular situation of the trees, according to our observa- tions, often makes a big difference in the development of this disease. Those on the edge of the forest, specially on the southern exposure, have often showed the disease first and most severely. Isolated clumps of sprouts in the open are very susceptible. Forests that have been opened up by removal of trees, especially if on hillsides with southern exposure, are where we find the blight most prominent. Also we have sometimes found it bad in the lowlands. All these represent conditions where the trees suffer most from lack of moisture under con- tinued severe drought. We have especially in mind a forest in Middlebury on a hill- side with southern exposure where the blight became very prevalent. There the trees unquestionably suffered severely from lack of moisture due to the droughts and the opening up of the forest by the removal of diseased trees. Many of those left finally showed sun-scald cankers with accompanying development of blight, at their base on the southern exposure, while the protected northern sides did not. Young nursery trees on this hillside also developed similar sun-scald cankers the first summer they were set out. While this part of the forest was being severely injured, trees on the northern exposure showed very little of the blight. This observation agrees with the statement of Ashe (Tenn. Geol. Surv., 10 B, p. n), who writes: "For many years the chestnut on the lower mountains in the southeastern portion of CONNECTICUT EXPERIMENT STATION REPORT, IQI2. the state has been dying out a few trees at a time. * * * Trees in the hollows and on cool north slopes and on land where a moderately dense shade and soil cover exist have not been affected. * * * The dying off of the trees is certainly not due to the chestnut bark disease." Local conditions such as outcrop of rocks, depth and character of soil, water table, presence of streams, exposure, etc., are all factors in the regula- tion of soil moisture,* and are not always easily determined by superficial examination. We *do know that the blight often acts quite differently with these conditions varying in the same vicinity. It is often hard to distinguish drought injury from winter injury, as trees that have suffered from severe droughts with- out much outward evidence of the trouble often succumb dur- ing the following winter, and winter injury is given the entire blame. This was well illustrated after the drought of 1911, by a number of fine large chestnut trees on the Experiment Station grounds. The drought of 1911, following the pre- ceding dry years, was very hard on certain of these trees, as the rock in spots comes very close to the surface. The result was that, following the winter of 1911-12 they were seen to be very badly injured at their base, the dead bark in some cases almost entirely encircling the trees. On one tree this dead bark ran up the side for a considerable distance. A little of the blight fungus showed on these injured areas shortly afterward, but it was entirely a secondary factor. There can be no question whatever that these droughts have injured various trees; and there is no getting around the fact that the blight has been more prevalent because of these droughts, and seems to have gotten the credit for injury to the chestnuts that is in part due to the droughts. Most persons admit that drought has injured and killed many trees other than the chestnut, yet are reluctant to concede that anything but the blight is responsible for the death of the latter. The injury by drought is well illustrated by the death of trees in * We understand that, due to the installation of a large water reservoir in the southwestern part of Long Island, the water table of the surround- ing region has been lowered considerably. This in turn has severely affected the forest trees, among which are many chestnuts. The blight is quite bad in this region. CHESTNUT BARK DISEASE. 399 East Rock Park, New Haven. This rock rises to a considerable height above the surrounding country, and the soil in many places is quite shallow, so that the trees have suffered severely from lack of moisture during the dry years. The chestnut has suffered with the other trees, and the blight has developed con- spicuously, killing many of them. Superintendent Amrhyn furnishes us with the following list of dead and dying trees that were found in this park in 1910. "I herewith enclose a list of dead trees found in the East Rock Park forests in an inspection made during the month of August, 1910. You will find the largest percentage of them to be chestnut and hemlock. The first were not all dead, but were severely affected by the blight. The hemlocks are all dead, but a few of them have been in that state for two or three years, while all affected or dead chestnuts were cut down last winter. Chestnut 1,362 Hickory 75 Beech 15 Hemlock 494 Maples 48 Elm 10 Oaks 271 Walnut 44 Linden 7 Birch 101 Wild cherry ... 24 Locust 4 Cedar 101 Ash 23 Sassafras 3 Carpinus 84 Pines 17 Apple 2 "I think that a very large percentage of these trees, 2,685, have died on account of the great dryness which has existed for about three years, changing conditions ever so much for the root systems of the trees." Other investigators have admitted the connection between drought injury and blight infection, or at least the possibility of such connection, as shown by the following quotations: Stone (Rept. 23, p. 57) says: "Our observations on the effects of meteorological conditions on vegetation, and the unusual opportunities we have had to study shade tree conditions for some years, have brought to our attention the unusually large amount of dead wood found on chestnut trees the past four or five years. From what we have seen of the chestnut during this period, we are of the opinion that it has not been in the best condition during late years, and that the chestnut, like the native white and black oaks, elms, red and rock maples, ash, etc., has been more or less affected by the severe cold and droughts of late years." A year later he writes further (Rept. 400 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. 24, p. 78) : "Like the preceding one, the past summer [1911] has been exceptionally dry, and the heat has been intense at times. This drought, coming as it did after three or four previous dry seasons, has affected vegetation to a considerable extent, and will result in later injury, especially to trees." Rane (54, p. 152) said: "The disease was worse where thinnings had been made and a few trees allowed to stand because they were not large enough to cut into ties. These forests were unbalanced, and the air and sun allowed to get in. The blight was on the southern side; the cankers showed up largely there, but in the stands where we had normal condi- tions we found only a diseased tree once in a while." Rankin (60, p. 47), in speaking of the relation of chestnut blight to drought, says: "Preliminary investigations carried on by the speaker seem to point to the fact that the susceptibility of the chestnut tree to this fungus depends upon drought con- ditions; that is, a low water content in the tree. * * * If the results of Doctor Moench on the cause of susceptibility and immunity of forest trees to disease should prove true in the case of this disease also, we may hope to be able to control the bark disease in shade, lawn and park trees by keeping up the water content of the tree." Dr. Caroline Rumbold (63, p. 57) states: "As for water, there is the question, as to whether or not droughts of recent years are partially responsible for the spread of the disease in the chestnut tree. I am now conducting experiments in which chestnut trees are being exposed to infection under vary- ing conditions, from dryness to excessive moisture, both atmos- pheric and soil. These experiments may also throw some light on the report that the blight spreads rapidly where trees are in a crowded coppice, while trees growing on the ridge of a hill are unaffected." Fire Injury. Not only the writer, but other members of the Station staff, have repeatedly noticed the blight on trees injured by forest fires. Examination of the region has usually shown that the blight was much worse on the trees within the fire area than on those beyond it. This fungus, in the writer's opinion, has not developed merely because of mechanical injury to the tissues, but rather because of lowered vitality of the inner bark and cambium. S. W. Eddy of Avon, in March, CHESTNUT BARK DISEASE. 401 1912, sent us specimens of the blight, and wrote: "We are enclosing you sample of what we think is the chestnut blight. As about 50 per cent, of the trees that were burned by forest fires last spring are covered with this growth, we desire very much to learn whether or not this is the blight." Mr. Eddy, in Feb- ruary of the following year, reported that he found the fungus abundant on the cut wood and fire-injured trees, but scarce on the perfectly healthy ones. Others have noticed this relationship of blight to fire injury, as shown by the following quotations. Rane (54, p. 152) says: "There is an unbalanced condition again where forest fires have run through the state year after year, and the trees are abnormal, and only half alive anyway. There you find the disease seems to travel more rapidly than it does where the trees are under normal conditions, and have a forest floor where there is plenty of moisture and the conditions are more favor- able." Buttrick, in a paper on the effects of forest fires on the trees (Forestry Quarterly, Vol. 10, No. 2), also remarks: "Diaporthe parasitica, chestnut bark fungus, seems to be more abundant and severe on fire-injured trees." Sprouts versus Seedlings. Much of the chestnut of Con- necticut has been cut over two or three times, being renewed by sprout growth. This repeated cutting has occurred not only in Connecticut, and in the greater part of New England, but in the chestnut forests of New Jersey, Delaware, and the eastern parts of New York, Pennsylvania and Maryland. It is generally admitted that this treatment has reduced the vitality of the coppice growth, as shown by the following quotation from R. Zon on the chestnut in southern Maryland (U. S. Dept. Agr. Bur. For. Bull. 53, p. 29) : "It must not be forgotten, however, that a chestnut stump cannot go on coppicing forever. With each new generation of sprouts, the stump becomes more and more weakened, and hence gradually loses its capacity to pro- duce healthy and vigorous sprouts. Although it is impossible to state with certainty how many generations of chestnut can be raised from the same stock without impairing the vitality of the sprouts, the effects of repeated and bad coppicing mani- fest themselves in the increasing number of dying chestnuts all over Maryland. The immediate cause of their death can nearly always be traced to attacks of either insects or fungi, yet the 402 CONNECTICUT EXPERIMENT STATION REPORT, 1912. prime reason is their decreased vitality, which makes them easy prey to their natural enemies." If the chestnut blight has no relation to the age or vigor of the tree, it is certainly a curious coincidence that the blight makes its first appearance and causes its greatest damage in the regions where the chestnut has suffered most from repeated cutting over. This is indicated by the two following statements. Nellis, of the United States Forest Service, in an unpublished working plan on "Utilization of Blight-killed Chestnut," writes : "It is expected that this study will show that the present range of the chestnut bark disease is in a region of entirely second- growth chestnut, which has been culled of its most valuable timber, where only rough products are now being produced." Barrus, of New York (54, p. 160), says: "In those sections of New York state where the chestnut disease is present most of the marketable timber has been cut out. Fire has gone through the remainder, and as a result, there is a great majority of the chestnut which is sprout growth of small dimensions. I should estimate that one-fifth of the chestnut is of merchant- able size, and perhaps in the districts where the disease is, more than four-fifths is under merchantable size." It has been our experience that young, especially isolated coppice growth, has suffered first and most severely in Con- necticut. We believe that these sprouts are naturally weak and easily killed by drought, etc. On the other hand, very large seedling trees have been the last to go with the blight. We noticed also, in our inoculation work, that it was somewhat easier to infect sprout growth than young seedling trees, and that the cankers on sprouts developed more rapidly. In June, 1912, we examined a field where the Ansonia Water Company had planted about seven bushels of chestnuts in 1908, in 1909 had set out 6,900 one-year seedlings, and in 1910, 9,875 two-year seedlings. While many of these seedlings had been killed by drought soon after they were set out, as shown by the vacant places, we were able to find only two seedlings that showed any signs of the blight fungus. Yet the woods surrounding these trees were quite badly infected with the blight. At one of the Connecticut nurseries, however, in September, 1911, we inspected about three hundred five-year-old American CHESTNUT BARK DISEASE. 403 seedling chestnuts which had been transplanted when one year old, and found 46 per cent, infected with the blight, which had been present there at least two years, and probably started at the time of transplanting. The roots of these plants, when examined, were in good condition. We had the superintendent cut off all the diseased trees in one row (sixty-nine), and in February, 1913, the sprouts that had come from these showed only one that was plainly infected with blight, although they were exposed to the blight from infected seedlings that had not been removed. The first-year sprouts from old stumps also rarely show infection. According to our infection experiments, it usually takes only a month for the canker to show after inoculation, so these one-year-old sprouts had time to show the disease if they were infected. We believe the old, well-estab- lished roots produced unusually vigorous sprouts, which for the time being, at least, escaped infection. Vitality versus Chemical Activity. We believe that favorable or unfavorable climatic conditions for a plant are recorded through chemical activities concerned with its growth and vigor, and that a lessening of this chemical activity might with some plants be shown by lessened resistance to fungous attack. The following few references show the relationship of environ- ment on chemical activities of certain plants. Hasselbring (Bot. Gaz. 53, p. 120) says: "It is true, of course, that plants are modified in their fluctuating characteristics by changes in the environment, but so far as experimental evidence shows, such modifications persist only as long as the environment inducing them persists. LeClerc and Leavitt, in their work with wheat, showed that this influence of the environ- ment is exerted also on the chemical composition of plants. When wheat of one variety from one locality was grown in other localities with a widely different environment, the chemical composition of the grain was different in each locality. These differences persisted as long as the wheat was grown in the particular locality, but if at any time seed from one locality was grown in any of the others, the grain took on the composi- tion of the wheat constantly grown in those localities. Vasey (U. S. Dept. Agr. Rept. 1872, p. 171) mentions a case where the alkaloids of cinchona bark were decreased by unfavor- able climatic conditions in the case of plants grown in England 404 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. as compared with plants grown in Peru. Yet when plants from England were sent to India, their vigor was restored, and an increase of the alkaloids was shown by chemical analysis, especially in the descendants of plants sent there. McKenney (Science 31, p. 750) writes concerning the blight of Central American bananas: "The juice of diseased plants contains much less tannin than that of the normal plants. * * * It has been proved that the disease is not due to local conditions, such as too wet or too dr> soil, etc. Yet some of these con- ditions may predispose the plants to the disease." He does not say whether the lessened tannic acid is the result of the disease or vice versa. Tannic Acid and its Relationship to Chestnut Blight. The chestnut as a source of tannin is one of our most important trees. However, it seems that most of this tannin is made from the chestnuts in the South, although they are utilized as far north as Pennsylvania. The reason for this is that the chestnuts in the South furnish a greater percentage of tannin than those in the North. At least one cause for this seems to be that the older the trees the greater the percentage of tannic acid, since the tannin is made from the ground wood and apparently comes largely from the older wood. As a rule, the chestnuts of the South are much older than those of the North, and are more likely to be seedlings. As yet the chestnut blight has not caused much harm in the South. Whether or not the present of more tannic acid in the trees there has any rela- tionship to the absence of the blight is as yet uncertain, but there is a possibility of its having a direct bearing. In answer to a question regarding variation of tannic acid in chestnut trees, Mr. F. Veitch, of the Leather and Paper Laboratory of the United States Department of Agriculture, writes me as follows: "I have your letter of the nth inst. asking for the tannin content of chestnut wood. This differs all the way from 2 per cent, to as high as 10 or 12 per cent, in very old, dry chestnut. The chestnut wood used by extract makers probably averages around 6 per cent, of tannin. I can make no more definite statement regarding the tannin content of any particular chestnut than to say that young chestnut as a rule contains the least, while the old chestnut contains the highest percentage of tannin. Only the body and large limbs CHESTNUT BARK DISEASE. 405 of the tree without the bark are used in the making of tannin extracts." W. M. Benson (54, p. 229) makes a statement regarding chestnut trees grown on different soils which, if true, possibly explains why, in very dry years, the trees suffer more from the blight than in wet ones, since there may be some relation between the amount of moisture and lime taken in by the roots and tannin produced in the tree. He says: "The chestnut wood received at the extract factories was at first supposed to be all alike in tannin strength, but costly experience proved that wood from good strong lime shale or limestone lands is far richer in tannin than wood from soils that are rocky, sterile, and contain little lime. The difference is so marked that even the workmen in the leach house at extract plants can tell when wood from a lime shale or limestone region is being leached simply by the unusual increase in the strength of the liquid obtained from such wood. Chemical analyses proved the same thing beyond all question, that in order for chestnut timber to attain its full tannin strength it must grow on lime- stone or lime shale soil." The part that tannin plays in the economy of plants is not very definitely known. It has generally been supposed to be largely a waste product, which serves more or less as a pro- tective agent against animal and fungus attack. Some few writers have raised the question whether or not it might serve some use in the physiological activities of the plant, possibly in the way of food. For instance, Pfeffer (Physiol. of Plants, i, p. 491-3) says: "Fungi can assimilate many aromatic bodies such as tannin, resorcin, hydroquinone, phloroglucin, etc., but except in the case of quinic acid most of these afford very poor food materials. * * * Tannins, phloroglucin, and apparently all aromatic substances which accumulate to any extent, are con- tained in solution in the cell sap, so that their presence does not injuriously affect the protoplast. * * * Tannins and glucosides are undoubtedly produced for definite purposes, and are not mere by-products produced under all circumstances. * * * In spite of numerous recent researches, but little is known as to the function of tannin." 26 406 CONNECTICUT EXPERIMENT STATION REPORT, Barnes (Textbook of Botany, i, p. 414) says concerning this subject: "Some substances, including the loose term tannin, are glucosides, and such as can be made to yield glucose by digestion may be considered as plastic substances rather than wastes." Stevens (Plant Anat, p. 205) also states: "Tannins seem to be by-products, set aside in the tannin cells from the general circulation. It is uncertain whether the tannins are ever used to an appreciable extent in nutrition. They seem to be of service, however, in warding off parasites by their aseptic qualities and astringent taste." Cook (Delaware Agr. Exp. Sta. Bull. 91, p. 59), who studied the effect of tannic acid on different species of fungi in artificial cultures, says in his general summary: "It appears that tannin is an important factor, and that its importance varies in accordance with the other substances with which it is associated in the cells of the host plant. While tannin no doubt serves as a protective agent, its efficiency in this direction will vary somewhat with the character of the other substances within the cell. This may account for the variation in power of resistance between species, varieties, and individual plants. The fact that plants which produce large quantities of tannin are subject to disease is no argument against the preceding. The organism may live in tissues which bear little or no tannin, or which contain other substances that in a measure counteract the influence of the tannin. Furthermore, some species of fungi are much more resistant to tannin than are others, and the species which attack these high tannin-bearing plants no doubt possess this quality." To the writer it has occurred that possibly tannin may serve as an unusual source of food for certain trees rich in this product under unfavorable conditions for active formation of their normal food supply, such as drought years, and that such a use would lessen the supply of tannin laid down in the annual growth of wood formed in these years. Or possibly if not used for food, these unusual conditions do not favor its normal production. In any case, if tannin content bears a relation to the blight disease, it is not the tannin of the whole tree that counts so much as the tannin of the bark and wood of that year's growth. If it bears any relation to the chemical activity of the tree, we can readily see that it could easily vary from CHESTNUT BARK DISEASE. 407 year to year according to external conditions more or less favorable for its production. In our tannic acid culture work with the true chestnut blight and its close ally, Endothia gyrosa, reported in detail later on, we found: (i) Both fungi can use tannic acid, at least in small amounts, as food, — shown by the blackening of media through oxidation, loss of acidity, more luxuriant growth, with a low per cent, of the acid added, than without it, and a slight growth on agar-agar with tannic acid as the available source of food. (2) Higher percentages of tannic acid (four per cent, and above) are detrimental to a vigorous growth of either of these fungi, and finally (10 to 14 per cent.) entirely inhibit their growth. But with the true blight the tolerance is apparently greater by 2 to 4 per cent, than that of the saprophytic E. gyrosa. (3) Long-continued cultivation of the parasitic variety in artificial cultures without tannic acid prob- ably lowers its tolerance to the higher percentages of tannic acid. (4) Gradually passing these fungi in cultures from the lower to the higher percentages of tannic acid apparently raises their tolerance to it. From the results of these cultural experiments and what we have been able to learn about tannic acid in the chestnut, we reason that the true chestnut blight is better able to become an active parasite on chestnut trees than the Endothia gyrosa. Any cause that would lower the tannic acid, etc., content of the trees would allow it to develop into a more vigorous para- site, and its gradual tolerance to this higher percentage of tannic acid would give it an added virulence up to a certain extent. With the return of the tannic acid, etc., content of the tree above this limit of tolerance, the fungus would gradu- ally revert to a less virulent and finally to even an inconspicuous parasite. PREVIOUS CHESTNUT TROUBLES. Nature of the Troubles. It is well known that in times past the chestnut trees in this country have suffered severely in cer- tain districts, particularly in the South, in some cases being practically exterminated, so that their range is now consider- ably lessened from what it was originally. Strangely enough, no one has surely accounted for any of these devastations. 408 CONNECTICUT EXPERIMENT STATION REPORT, 1912. Personally we believe that this tree is extremely susceptible to changes in the natural environment, and that such changes, with water playing an important part, have been the chief factors back of the gradual decline of this important forest tree. Other factors, such as forest fires, deterioration through repeated cuttings, insect and fungus attacks, are contributing causes varying in different localities. The question naturally arises, has the blight fungus had anything to do with these previous troubles of the chestnut? As no one ever made a careful study of them at the time, it is impossible to state whether or not the blight was connected with them. One thing is certain, and that is that the sapro- phytic Endothia gyrosa is so generally scattered over the South to-day that there is no doubt it occurred in the regions where these chestnut troubles existed. It seems almost equally certain that the real chestnut blight does not to-day occur in those regions, or if it does, it is very inconspicuous. This would seem to indicate that if the blight had anything to do with these troubles in the past it was not able afterwards to exist there, but gradu- ally extended northward. When one reads the accounts of the outbreaks, he can easily imagine that the trouble might be due to the blight fungus. We give here, arranged according to the time of their occurrence, some references to these troubles. 1825-45. We quote the following from an article by Mr. Jones of Georgia, which appeared in the American Journal of Science, Vol. i, p. 450, in 1846: "The present remarks are particularly directed to the death and disappearance of some of our trees and shrubs. The first that I will mention is the Castanea pumila, which is a -tree from ten to thirty feet in height. In the year 1825, during the months from June to September, I observed this tree dying when in full leaf, and with fruit half matured. I examined numerous individuals, and could find no internal cause for their dying. I at first attributed it to the great fall of rain which took place in the year 1823. During the month of July of that year a consider- able quantity of land not subject to overflow was covered with water for some time, and the highest lands were completely saturated. The latter part of 1824 was also very rainy. Know- ing that this tree belongs in our highest and dryest soils, I con- cluded it was owing to a too moist state of the ground, but CHESTNUT BARK DISEASE. 409 since that time I am convinced that there must be some other cause, for the tree continues still to die up to the year 1845, and if the disease is not arrested, in a few years I fear it will be entirely exterminated." 1856. Following is a letter from Professor G. W. Hilgard, received October 25, 1909 (similar observations by him have been recorded by Dr. Rumbold in Science, Vol. 34, p. 917) : "Your paper on the chestnut disease in New England reminds me of some old observations of mine made in the state of Mississippi in 1856. Traveling in the pine hills of northeastern Mississippi, I noted that of the small percentage of chestnut trees among the pines only a few were living, the great majority, mostly very large, tall trees, dead and decaying. On inquiry of the inhabitants, I found that this deadening had occurred lately, and they were at a loss to account for it. To my question why so many were charred at the base, the reply was that when the boys wanted to make a fire for nooning, they made it against these trees because they burned easily. The trees had not been killed in that way, but had died 'of their own account/ No other kind of trees seemed to be diseased. It was distinctly a dying off of the chestnut alone, and it extended far into Alabama. It would be interesting to know whether the results of that epidemic have been permanent, or whether a new growth has come since the time I saw it. If the Diaporthe disease existed in Mississippi, the presumption is that it extends or extended all along the western Alleghany slopes, and has perhaps reached the Atlantic Coast only recently." 1856. This note was found in The Horticulturist, 1856, p. 97 : "All the chestnut trees throughout Rockingham County, North Carolina, and the surrounding counties have died this season." 1^55-75. The following references are taken from an article on Statistics of Forestry in the U. S. Dept. Agr., 1875, p. 262, and are concerning chestnuts in the southern belt: "In several localities chestnut for some undiscovered reason appears to be dying out." Under notes on forestry conditions in Henry County, Va., is the following statement: "Chestnut has been dying out for years, and there are fears that it will become extinct." Concerning Elbert County, Ga., is the following: "The forests are a mixture of almost all kinds, but chestnut during the last twenty years has nearly died out." Under 410 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. Carroll County, the same state, is the statement: "The forests contained a large quantity of chestnut, which began to die about ten years ago, and now scarcely a tree is left. Even the bushes are nearly all dead, though no insect or worm or other cause affecting them has been discovered." From Hall County also it is said: "Until within a few years chestnut abounded, but now nearly every tree is dead or dying." And from Walton County : "The chestnut has all died." 1847-77. Under Diseases oT Chestnut, p. 116, A. S. Fuller, in The Nut Culturist, published in 1896, writes: "I have never noticed any special disease among chestnuts, neither do I find any mentioned in European books on forestry. The nearest approach to any such malady being recorded as having appeared in this country, is found in a paragraph in Hough's Report on Forestry, 1877, page 470, where the author copies from Pro- fessor W. C. Kerr, state geologist of North Carolina, as follows : 'The chestnut was formerly abundant in the Piedmont region down to the country between the Catawba and Yadkin rivers, but within the last thirty years they have mostly perished. They are now found east of the Blue Ridge only, on higher ridges and spurs of the mountains. They have suffered injury here, and are dying out both here and beyond the Blue Ridge. They are much less fruitful than they were a generation ago, and the crop is much more uncertain.' While there is nothing said about chestnut disease in the paragraph quoted, we only infer that the author intended to convey the idea that the trees were suffering from some endemic malady, although it may have been due to long droughts, insect depredators, or other causes. A few years later Mr. Hough, in his Elements of Forestry, refers to the subject again, and admits that 'the cause of the malady is unknown.' But as the chestnuts continue to come to our market in vast quantities from the Piedmont regions, there must be' a goodly number of healthy trees remaining." 1889. On this date, P. H. Mell, in the Ala. Exp. Stat. Bull. 3, p. 16, says: "The trees [chestnut] of this state seem to be subject to a blight, or some destructive disease that is rapidly destroying them. This is particularly true when other trees are cut around them. This subject is worthy of careful investi- gation, and will be a problem for the experiment station to CHESTNUT BARK DISEASE. 411 solve in the future." Recently writing to Professor Mell regarding this trouble, he replied: "In reference to Bulletin 3 of the Alabama Experiment Station in regard to the disease which attacked the chestnut trees in Alabama during 1889, I do not think investigation was ever carefully carried out." Atkinson, former, and Wolf, present botanist, at the Auburn Station are unable to throw any additional light on this trouble. 1894. G. McCarthy, in N. Car. Exp. Stat. Bull. 105, p. 267, says concerning chestnut in this state: "The woodman's axe, casual fires, and the ravages of the root disease, have wrought much havoc with these grand forests." —1896. W. P. Corsa, in Nut Culture in the United States, a special report of the U. S. Dept. Agr., Div. Pom., published in 1896, p. 78, writes: "From causes not well understood, there is a marked decline in the vigor of the chestnut throughout the broad area of territory in the Southern States where the white man found this tree among the most thrifty of the original forests. Down to the first quarter of the present century there seems to have been no mention of a trouble in the chestnuts of that section. Within the memory of residents of the Gulf States the chestnut flourished in all their higher lands. In point of time the trouble seems to have begun in the most southern limit of chestnut growth, and there the destruction has been most complete. It has pushed its encroachments throughout Mississippi, Alabama, Georgia, and South Carolina, and is now reported in the strongholds of chestnut growth in North Carolina, Tennessee and Virginia. Observation of the native chestnut growth of Maryland and Virginia discloses the fact that many trees are dying without apparent cause. In some sections this is attributed to the ravages of insects. In others, to an unknown disease resembling blight. There is need for a more thorough investigation of this subject than has yet been made. No injury to the Japanese or European chestnut planted in this country is yet reported." — ipoi. Dr. Mohr, in Plant Life of Alabama, published by the U. S. Dept. of Agr., Div. Bot, in 1901, page 61, states: "The chestnut, usually one of the most frequent trees of these forests, is at present rarely found in perfection. The older trees mostly show signs of decay, and the seedlings, as well as the coppice growth proceeding from the stumps, are more or less 412 CONNECTICUT EXPERIMENT STATION REPORT, 1912. stunted. It is asserted by the old settlers that this tree is dying out all over the mountainous regions, where at the beginning of the second half of the century it was still abundant and in per- fection." — jp/i. W. W. Ashe, in Chestnut in Tennessee, Tenn. Geol. Surv. Bull. 10 B, p. n, remarks: "For many years the chestnut in lower mountains in the southeastern portion of the state has been dying out a few trees at a time. * * * The dying off of the trees is certainly not due to the chestnut bark disease, a very destructive malady from Virginia to southern New England, no evidence of which was seen in Tennessee." — 1912. Dr. Hopkins (54, p. 180), of the United States Dept. of Agriculture, who has recently been making a study of the relationship of insects to the death of chestnut trees in the South, states: "When we review the history of the extensive dying of chestnut during the past half century in Mississippi, Tennessee, Georgia, South Carolina, North Carolina, and Vir- ginia, it is surprising that there are any living trees left. In fact, there are not many left in some sections of these states, where the tree was abundant and healthy fifty years ago. It appears that there are a number of agencies of destruction other than the new chestnut blight disease, and that these agencies have been in operation in the area affected by the disease as well as in areas where this disease is not known to occur. Therefore, they must be taken into consideration and investigated before the problem of protecting the chestnuts can be solved. There appear to be other diseases, and we know that there are insects which have been directly or indirectly the cause of the death of a large percentage of the chestnuts over extensive areas." — 1913. Professor H. R. Fulton, of the Agricultural Experi- ment Station, West Raleigh, N. C, under date of January 29, 1913? writes: "Throughout the whole Piedmont section of this state, just as in the corresponding section of Virginia and further south, the chestnut trees are in an unthrifty condition. This is probably due to a combination of factors. Changes in soil conditions due to a clearing up of extensive areas probably play a part. Trees are evidently attacked to a considerable extent by borers and other insects. Fire injury has in many instances had something to do with the situation. Our preliminary survey CHESTNUT BARK DISEASE. 413 of the field has not disclosed any fungous disease that seems to be importantly connected with the condition of the trees." NATIVE HOME OF THE FUNGUS. General Considerations. Previous to the work of Merkel and Murrill, no one had ever, so far as known, collected or described the true chestnut blight fungus. Its sudden and destructive appearance naturally leads to the question, — Where did it come from? Murrill has not tried to solve this problem, although we understand he at first believed it to be a native species. The writer is the only one who, claiming it a native species, has attempted to give definite reasons for the belief, and an explanation of its sudden and aggressive development. Others have come forward with the suggestion that it is an introduced parasite, brought in accidentally, either from Japan or Europe. They have been led to their belief apparently largely because the blight was reported at first from a restricted region around New York City, and has apparently since then spread from this center into the regions in which it is now known. We shall consider in the following paragraphs each of these possible habitats for this fungus. Japan. Metcalf has suggested most definitely that the fungus originally came from Japan, and Marlatt (31), following this suggestion, gives the blight as one of the most striking examples of "why we need a national law to prevent the importation of insect-infested and diseased plants." Metcalf 's (33*, p. 4) first statement concerning the native home of this fungus is as follows: "The immunity of the Japanese chestnut, together with the fact that it was first introduced and cultivated on Long Island and in the very locality from which the disease appears to have spread, suggests the interesting hypothesis that the disease was introduced from Japan. So far, however, no facts have been adduced to substantiate this view." Later, Metcalf and Collins (36, p. 46) say: "Investigations are in progress to determine the origin of the bark disease in America, and the details regarding its spread. The theory advanced in the previous publication of this Bureau that the Japanese chest- nuts were the original source of infection has been strengthened by many facts. It lacks much of demonstration, however, and 414 CONNECTICUT EXPERIMENT STATION REPORT, 1912. is still advanced only tentatively. * * * Chester's Cytospora on a Japanese chestnut noted at Newark, Del., in 1902, may have been the bark disease." Recently Metcalf (35, p. 222) remarks: "Its origin is unknown, but there is some evidence that it was imported from the Orient." Later, in answer to a direct question as to its origin, he adds (p. 227) : "That is exactly what we would like to know more about. The fa£t that the disease has obviously spread from a center leads me to believe that it is an importation rather than a disease which has developed here. The fact that the locality from which it has spread is the same locality into which the Japanese chestnut was first extensively intro- duced, that the Japanese and Corean chestnuts are highly resistant, and are the only varieties that are at all resistant, all suggest the hypothesis that the fungus parasite may have come from the Orient. However, the origin of the parasite is not a matter of practical importance, unless it could be shown that the fungus parasite is developing spontaneously in many locali- ties from some native saprophytic form, in which case the difficulties of control would be greatly increased." In the preceding, Metcalf brings out four points in favor of the Japanese origin of the fungus, as follows: (i) Immunity of Japanese and Corean chestnuts; (2) Outbreak of disease originally in Long Island, where Japanese chestnuts were first imported; (3) Spread of the disease from a single center: (4) Possibility of Chester's Cytospora on Japanese chestnut being the blight fungus. Let us take up these four points for further consideration. (i) The immunity of Japanese chestnut does not necessarily mean that this fungus occurred on it in Japan, and when brought to America spread to the American chestnut, and, finding it a more favorable host, caused the serious outbreak here, as Metcalf suggests. It may merely mean that the Japanese is a more hardy species. From the statements of Morris (13, p. 43) we take it that this is the case, since it is only the Japanese or Corean varieties from the more northern regions that show this resist- ance. Recently it has been found that the Japanese chestnut is highly resistant to the black canker, a serious chestnut disease now causing trouble in France. Arguing along Metcalf 's theory, one could say that this French fungus was of probable Japanese CHESTNUT BARK DISEASE. 415 origin, which no one claims, so far as we know. Again, neither the chestnut blight fungus nor the closely related Endothia gyrosa has ever been reported from Japan, so far as the writer has been able to learn. In order to look into this matter a little more thoroughly, we wrote to three of the leading Japanese mycologists on this point. None of them could give us any information of the occurrence of these fungi there, or of any serious chestnut trouble that could be attributed to them.* One of them naively answered: "Some botanists in your country seem to entertain the opinion that this chestnut blight fungus is of Japanese origin, — an apparently plausible opinion in accord- ance with a popular belief in certain quarters of your country that things obnoxious come from the other side of the Pacific. Let us see whether the words of these chestnut prophets prove to be the fact or not." (2, 3) We have attempted, under the head "Manner of Dis- tribution," to show that this disease did not originate in one locality, where first reported, and that its spread has not been from a single, but from many centers. (4) Regarding Chester's Cytospora on Japanese chestnut, we can say definitely that this was not the blight fungus. We are indebted to the Delaware Experiment Station for the opportunity of examining the herbarium specimen of this, and we find that it is an entirely different fungus, being similar to a Phoma-like fungus not uncommon on dead and dying chestnut sprouts. Europe. While Farlow (20, p. 70) was one of the first to call attention to the very close relationship, if not exact identity, of our chestnut blight with Endothia gyrosa as found in Europe, he has made no claim that the disease was introduced into this country from Europe. He merely asks, "Is Diaporthe para- sitic a, as at first supposed, really a species new to science? If so, is it a native species which has hitherto escaped the notice of all mycologists, or has it been introduced from some other country?" One can infer from his article, however, that if the fungus was proved to be an imported one he would favor Europe rather than Japan as being its native home. Shear (65, p. 212), however, comes out with a more definite statement as regards the European origin of the fungus, as follows: "As a result of our studies to date, we are of the opinion that Diaporthe parasitica Murr. is the same as Endothia 41 6 CONNECTICUT EXPERIMENT STATION REPORT, 1912. radicalis of European authors, but not of Schweinitz, and that it was probably introduced into this country from Europe, and has gradually spread from the original points of introduction, its spread being facilitated chiefly by borers or other animal agencies which produced wounds favorable for infection by the fungus." Shear's reason for supposing that the chestnut blight was imported from Europe was th^.t Endothia gyrosa occurred on chestnut there, and he could not distinguish the American chest- nut blight from this fungus. He, however, apparently did not know that E. gyrosa (E. radicalis of some European authors) also occurred on chestnut in this country. Further, he (66) was misled by an incorrectly named culture received from Pantanelli (supposed to be of European origin but later turning out to be the real blight from America) with which he produced the disease in chestnuts. Pantanelli (53) of Italy, who has recently made a study of the European Endothia gyrosa and the American chestnut blight, finds ( i ) that they are different in many small microscopic char- acters; (2) that, while E. gyrosa varies somewhat in character in Europe, there are no variations that correspond to the chestnut blight type; (3) that the native E. gyrosa causes no serious disease in Europe; (4) that the American chestnut blight, when inoculated into chestnut in Italy, produces the disease. Natur- ally he concludes that our chestnut blight cannot be of European origin. To the above we might add the fact that European chestnut grown in this country is quite susceptible to the blight, and it would be rather difficult to explain its susceptibility in this coun- try and its immunity to the native fungus there, unless environ- ment really did bear some relationship to susceptibility and immunity of the host, which is denied by Metcalf. United States. The writer's reasons for believing the chestnut blight is native to this country may be summarized as follows : (i) It has never been found in any other country. (2) It is very closely related to Endothia gyrosa, apparently developing from it as a distinct variety, and this species is a native fungus in this country as well as in Europe. (3) The limits of distribu- tion of E. gyrosa and the chestnut blight overlap at least in the region covered by Washington, D. C, to southern Pennsylvania, CHESTNUT BARK DISEASE. 417 while E. gyrosa occurs south of this common area and the chest- nut blight north of it. (4) We have previously had serious troubles of chestnut trees in this country, and there seems to have been a continued northward movement of these, culminating in the recent trouble in the northern limit. While the chestnut blight has been definitely connected only with this last trouble, the pre- vious ones have never been really explained. (5) The sudden- ness, etc., of the recent blight outbreak has been adequately explained by the writer through the unusual environmental con- ditions that have weakened the chestnuts in the general regions where the outbreak has occurred. (6) The fact that the chestnut blight fungus was never reported before this outbreak is no more difficult to explain than the fact that E. gyrosa had never been reported on chestnut in this country until by the writer a year ago, and yet this is a native fungus widely distributed on chestnut in the South, and has been known there on other hosts since 1822, when described by Schweinitz. They both were, in fact, merely overlooked on the chestnut. (7) Our cultures of E. gyrosa vary more from their normal type than do those of the variety parasitica, and some of these have varied somewhat toward the variety parasitica type. This, however, may have been due in part to bacterial contamination, etc. AMERICAN SPECIES OF ENDOTHIA. Various Species. It has been agreed among those who have recently studied the blight fungus from a systematic standpoint that it belongs under the genus Endothia rather than under Diaporthe, and is at least very closely related to the American- European species Endothia gyrosa. So far there have been described under the genus Endothia comparatively few species. Fries, who founded this genus, apparently considered Sphaeria gyrosa as the type, but did not give a very complete generic description. As understood to-day, however, Endothia has quite distinct generic characters. Of the species other than Endothia gyrosa and the chestnut blight, there have been found in North America Endothia Parryi (Farl.) Cke., on Agave sp., Endothia longirostrata Earle, on the bark of fallen trees from Porto Rico, and Endothia radicalis (Schw.) Farl., on Quercus, etc., chiefly from the Southern states. 418 CONNECTICUT EXPERIMENT STATION REPORT, 1912. Besides these, there is a somewhat similar appearing fungus recently described, by H. & P. Sydow (Ann. Myc. 10, p. 82) on Quercus from Colorado, as Calopactis singularis. It is a semi-parasitic species, apparently, whose generic position is some- what doubtful, as the asco-stage has not been found. It has been known in this country for some time, and by some botanists has been placed under Endothia gyrosa, since the fruiting pus- tules and the Cytospora spores of the two are very similar. However, the fruiting pustules are larger, deeper crimson in color, and in maturity more powdery. We have it in culture from a specimen recently sent by Bethel from Colorado, and while it grows something like E. gyrosa, it does not form any distinct conidial fruiting pustules on media tried so far, and in manner of growth and color of mycelium resembles more nearly the cultures of E. radicalis. Of the species mentioned, we need to consider in connection with the blight fungus only Endothia gyrosa, already discussed somewhat, and Endothia radicalis, since these three in their Cytospora stage are so similar in appearance that they cannot be distinguished by the naked eye, and all have at least the oak as a common host. As E. radicalis is most sharply set off from the other two, we will discuss it first. Endothia radicalis. While the fruiting pustules of this species are not different from the other two, when we examine the asco- stage under the microscope it is very easily distinguished by the much narrower spores. These ascospores vary from linear to linear-oblong, are occasionally slightly curved, are apparently single-celled, though possibly they may in some cases develop an indistinct septum, and are 6-10 /M, rarely 12 /*, . long by 1-2 /A wide. We have never seen spores which grade into those of the other two species described here, so it is apparently quite a distinct species. See Plate XXVIII a, d. It seems to be largely southern, having been found in its asco-stage in Louisiana, Mississippi, Georgia, Alabama, Florida and North and South Carolina. However, there are specimens in various herbaria from much further north, xshowing only the conidial stage, that apparently belong to this species. One speci- men found in Connecticut has been under observation on roots of an oak tree for over a year, and though in a vigorous grow- ing condition, has made no attempt to form the asco-stage. CHESTNUT BARK DISEASE. 419 Artificial cultures, however, show that it is this species. This means, apparently, that the species does not form its asco-stage readily in the North. It has not been reported as yet from Europe or elsewhere. While it seems to be largely saprophytic, we recently received from Wolf, of Auburn, Ala., an elegant specimen on the live trunk of water oak, that shows it possesses parasitic tendencies. Plate XXIV e. So far this fungus has been reported on several species of Quercus and on Liquidambar Styraciflua. Earle and Under- wood collected what may be this species on Vitis. Schweinitz described his Sphaeria radicalis as rare on roots of Fagus, though on the envelope containing the original specimen he states it is on the roots of Quercus, which seems more likely. However, we have recently received ample specimens collected by Hall, at Clemson College, S. C, on the roots and bark of Fagus, which proves that this is to-day a host of the fungus further south, and so it may have been at Salem, N. C., as stated by Schweinitz. In cultures it forms a rather abundant aerial mycelium, something like Endothia gyrosa, but differs in that this is much more fluffy in character, and does not usually form fruit- ing pustules on the surface of the agar, Plate XXVI 7596. The conidial spores are produced in rather indefinite spots on the mycelium, and are very similar in appearance to those of the other two species, Plate XXVIII g-i. The mycelium lacks the bright orange color that is characteristic of Endothia gyrosa on most media. At first it is white, and often remains partly uncolored, but finally has considerable brownish orange color, especially next the glass on the surface of the agar. In Petrie dishes the mycelium often forms a somewhat annulated develop- ment by the newer growth being less elevated than the older. We have cultures of it from Liquidambar Stryraciflua and Quercus nigra, from Alabama; Fagus ferruginea, Quercus coccinea, and Quercus sp., from South Carolina ; Quercus falcata, from North Carolina; and Quercus rubra, from Connecticut. There is considerable doubt as to who first described this species, since it has usually been confused with the next. Shear (64) speaks of it as Endothia radicalis (Schw.), thus identifying it with Sphaeria radicalis of Schweinitz; and the Andersons seem to think that Shear definitely proved it to be identical 420 CONNECTICUT EXPERIMENT STATION REPORT, 1912. with that species. No Schweinitzian specimens of Sphaeria radicalis in this country, however, have yet been found which have ascospores, though there is no doubt from the specimen in the conidial stage in the Schweinitzian collection in the Philadelphia Academy of Science that 5\ radicalis refers either to this species or to E. gyrosa. As Shear had opportunity to see certain specimens of 5". radicalis and 5\ gyrosa sent by Schweinitz to European botanists, the writer thought he had found the ascospores of 5\ radicalis to be linear. Recently writing Shear on this point, we received the following letter: "The specimens on oak roots collected by Hall in South Carolina which I identified as the typical S. radicalis of Schweinitz were, according to my recollection, compared with authentic specimens of Schweinitz from either Schweinitz's herbarium or Curtis' herbarium at Harvard. This identification was made last winter before my trip to Europe. I have been going over carefully all our slides and specimens to locate the material on which this identification was based. I regret to say that thus far I have been unable to find it. In this same connection I have examined very carefully the material from the Kew herbarium, which consists of an autograph specimen collected by Schweinitz, presumably at Salem, N. C, and sent by him to Hooker. I am surprised to find, on examination, that this specimen, though it shows considerable variation in ascospore measurements, does not appear to agree with the long, slender form of ascospores found in the specimen on oak roots which I sent you from Hall's collection at Clemson College, S. C. The measurements, as they have just been made from a slide from the Kew specimen, range mostly from 6.3-8.6 by 2.8-3.6 ^. I think it is still possible that all sorts of inter- mediate forms and sizes of spores will be found in the South connecting the long and short-spored specimens." Writing to the Kew herbarium for information concerning the specimen mentioned by Shear, which seems to be the only Schweinitzian ascospore specimen of Sphaeria radicalis yet reported, we received a letter from Assistant Director Hill, with the following notes made by E. M. Wakefield: "The specimen referred to by Shear appears to be one which bears simply a pasted-on rough paper label with the name 'Sphaeria radicalis' in ink. On the authority of Mr. C. G. Lloyd, who is working CHESTNUT BARK DISEASE. 42! here at present, the handwriting is that of Schwaegrichen, and the specimen is an authentic Schweinitzian one. It is probably one of a set sent to Hooker, though there is nothing on the label to indicate that this was the case. There is a pencil refer- ence in another handwriting (apparently Berkeley's) to 'Fr EL 2 P- 73- Versatiles.' Some ascospores have been found in this specimen from which the accompanying drawing has been made. They measure 5-7.5x2-3 /A (average size about 7x2 /«). The spores are usually one-septate. The septa are indistinct unless stained." From Shear's and Wakefield's measurements of the spores, one can readily see that the specimen in the Kew herbarium labeled Sphaeria radicalis is not the species we are considering here under that name, but really the next species, Endothia gyrosa. In a previous publication (9) we stated our belief that Schweinitz's S. radicalis and 5\ gyrosa represented either the two distinct species of Endothia that we now find in the south- ern United States or else the conidial and the asco-stage of only one of them, most likely S. gyrosa. This Kew specimen points to the latter of these two conclusions. It has also been the opinion of certain European botanists that these two species of Schweinitz were merely synonyms, and identical with the form found in Europe, which we call Endothia gyrosa. Ellis (N. Am. Pyren. p. 552) in his description included both of these species (his spore measurements relating to one and his drawings to the other), though most of the specimens he referred to are those with linear spores. Farlow (20) was the first to really point out the two as distinct species, and because of this we (9) previously referred to the linear-spored form as Endothia radicalis (Schw.) Farl., though Farlow never definitely used this combination for the fungus. While at present it seems somewhat doubtful if Schweinitz's Sphaeria radicalis really relates to this fungus, we shall retain this com- bination, hoping for further light on the subject through future investigation. On the other hand, there is little if any doubt that Schweinitz's Peziza cinnabarina does relate to its conidial stage, since it is identical, and has Liquidambar for a host, a host upon which E. gyrosa has not yet been reported. The nomenclature already used for this fungus by different writers is as follows : 422 CONNECTICUT EXPERIMENT STATION REPORT, 1912. Endothia radicalis (Schw.?) Farl. Peziza flammea Schw. (not Alb. & Schw.) in Fung. Car. Sup. n. 1193. 182-2. Peziza cinnabarina Schw. N. A. Fung. n. 840. 1831. ? Sphaeria radicalis Schw. N. A. Fung. n. 1269. 1831. Sphaeria gyrosa Schw., Ravenel in Fung. Car. n. 49. 1852. Lachnella cinnabarina Sacc. Syll. Fung. 8 : 399. 1889. Endothia gyrosa (Schw.), Ell. & Ev. in N. A. Pyren. : 552. 1892. p.p. Endothia radicalis (Schw.), Shear in Phytop. 2:88. Ap. 1912. Endothia radicalis (Schw.) Fr., Andersons in Phytop. 2:210. O. 1912. Endothia radicalis (Schw.) Farl., Clinton in Science 36:910. D. 1912. Endothia gyrosa. We have examined ascospore specimens of this species on Castanea dentata from several southern states; on Castanea sativa from two sources in Italy; on Quercus alba, O. velutina, Quercus sps. from several localities in America; on Quercus sp. from Italy; on Carpinus Betulus from Tiflis, Russia ; on Carpinus sp. from Italy. So far as we can tell from a microscopic examination, these all belong to the same species, though there is some slight variation of the ascospores in the different specimens. These ascospores vary from elliptical oblong to narrowly oval, often tapering to one or both ends, have an evident septum, and are chiefly 6-9 /x long x 2-3.5 P wide. They are therefore quite distinct from those of the preceding species (see Plate XXVIII b, e). Saccardo gives Aesculus, Alnus, Corylus, Fagus, Juglans and Ulmus as reported hosts for this species, with a distribution including North America, Europe, Ceylon, and New Zealand. But a careful comparative examination would be necessary to state positively that these all relate to the same fungus. We have made cultures of this fungus from many different sources on chestnut and oak from the South, and on chestnut from Italy. See Plate XXVI 7590, 7584. While these show some slight variations, they have a general agreement, but differ decidedly from all cultures of the true chestnut blight. We have made inoculation tests, and have found the fungus CHESTNUT BARK DISEASE. 423 to be a saprophyte, but with weak parasitic tendencies. Both the cultures and the inoculations we will discuss later in connection with those of the true chestnut blight. From the name usually applied, Endothia gyrosa (Schw.) Fr., it is seen that Schweinitz's Sphaeria gyrosa is considered the original type of the species. Schweinitz, in his Fung. Car. Sup., 1822, described this from Salem, N. C, on decaying bark of knots and also living bark of Fagus and Juglans. There is to-day some doubt about his correct determination of these hosts. He sent specimens to Fries, who also described it in his Syst. Myc. 2, p. 419, in 1823; and in his Elench. Fung. 2, p. 84, in 1828, he compares it with specimens received from Southern Europe. In 1845, Fries, in Summ. Veg. Scand., created a new genus, Endothia, citing v$\ gyrosa of Schwei- nitz as the type, and ever since then European botanists have considered Endothia gyrosa of Europe to be the same fungus as Sphaeria gyrosa, described by Schweinitz from America. Some few have given Fuckel as a second author- ity for the name, E. gyrosa (Schw.) Fckl., since that author in his Sym. Myc. p. 226, in 1869, indicated that he was the first to place this species under this genus, evidently con- sidering that Fries had not properly placed it there, since he did not really write the combination Endothia gyrosa. From the descriptions of both Schweinitz and Fries, it looks as if Schweinitz collected only the Cytospora stage of this fungus. This is further borne out by the fact that Schweinitzian specimens examined by Farlow and Shear in this country and Europe show only that stage. The original specimen of Schweinitz at the Philadelphia Academy of Science has been lost or misplaced, and in the original envelope is an entirely different fungus, a Nectria sent by Torrey from New England, which Schweinitz years afterwards apparently mistook to be this species. The writer (10) found a misplaced specimen (in another collection made by Schweinitz, now at the Philadelphia Academy of Science), which probably is his original type, but this also shows only the conidial stage. In the Curtis collection at Harvard, however, there is a Schweinitzian specimen of 5". gyrosa which, while in the conidial stage, has a drawing on the envelope by Curtis of ascospores which are like those of this 424 CONNECTICUT EXPERIMENT STATION REPORT, 1912. species rather than linear, like those of E. radicalis, already discussed. Both Schweinitz and Fries always considered Sphaeria gyrosa and S. radicalis as distinct species, but of very similar appear- ance, and Fries, when he formed the genus Endothia, did not include the latter under it. Botanists in their day, however, did not make very careful microscopic examinations. De Notaris, in Sfer. Ital. i1, p. 91, in 1863, seems to have been the first to place 5. radicalis under the genus Endothia, and Tulasne, in Sel. Fung. Carp. 2, p. 87 and p. 298, the same year, was apparently the first to consider the S. gyrosa and S. radicalis as one species, which he called Melogramma gyrosa. Fuckel also, in 1869, treated them as one species, and since that time European botanists have generally considered them as a single species, using sometimes E. gyrosa and sometimes E. radicalis as a specific name. In view of the information already given in Shear's letter, we are inclined to believe that this interpretation is correct, and that 5". gyrosa is merely the conidial stage, as first suggested by Winter in Rab. Krypt. Fl. i2, p. 804. A considerable number of names have been applied in Europe to Endothia gyrosa, but it is rather difficult to determine whether all of these apply to the fungus under discussion. For instance, Streinz, in Nom. Fung., p. 545, in 1862, under ,S. gyrosa, gives 5\ fluens Sow. as a synonym, and under S. radicalis, p. 559, gives S. tuberculariae Rud. as another. Shear has examined the Sowerby specimen, and he says: "There is little doubt that Sphaeria fluens Sow., described and figured by Sowerby in the supplement of his English Fungi, 1814, Plate 420, published as part of Plate 438, from a collection by Charles Lyall, in the New Forest of southern England, is the pycnidial condition of Endothia radicalis De Not." If this is true, then it must be an extremely rare fungus in England, since in answer to a letter to the Kew herbarium we received the reply that " Endothia gyrosa is very rare in Britain, if it really occurs." From Sowerby's description, one cannot be sure if it relates to this or some other fungus. Mr. Wakefield of Kew writes concern- ing our inquiry as to the host: "It is not possible to say with certainty what is the host of Sowerby's Sphaeria fluens. The specimen is very small, and no note is attached to it." We do not believe that this English specimen has as yet been definitely CHESTNUT BARK DISEASE. 425 identified as the same thing as Endothia gyrosa. We give below the nomenclature which probably applies to the fungus in question. Endothia gyrosa (Schw.) Fr. f Sphaeria fluens Sow. Eng. Fung. t. 438 (with t. 420). 1809? Sphaeria gyrosa Schw.* Fung. Car. Sup. n. 24. 1822. Sphaeria Tuberculariae, Rudolphi in Linnaea 4:393. 1829. f Sphaeria radicalis Schw.f N. A. Fung. n. 1269. 1831. Endothia gyrosa Fr. Summ. Veg. Scand. : 385. 1845. Diatrype radicalis Mont. Ann. Sci. Nat. Bot. 3 : 123. 1855. Falsa radicalis Ces. & De Not. «$chem. Sfer. Ital. : 33. 1863. Endothia radicalis De Not. Sfer. Ital. i1 : 9. 1863. Melo gramma gyrosum Tul. Sel. Fung. Carp. 2 : 87. 1863. Nectria gyrosa B. & Br.J Journ. Linn. Soc. Bot. 15 : 86. 1877. Chry phone ctria gyrosa Sacc.J Syll. Fung. 17:784. 1905. Endothiella gyrosa Sacc. Ann. Myc. 4 : 273. 1906. Endothia mrginiana Anders. Phytop. 2:261. D. 1912. Endothia gyrosa var. parasitica. We have previously spoken of the very close connection of Endothia gyrosa to the chestnut blight, and have shown that Farlow and Shear in this country, and von Hohnel, Saccardo and Rehm in Europe recognize them morphologically as a single species. Recently we sent ascospore specimens of the two on chestnuts from this country to these European botanists for further comparison, and their opinion as to the relationship. They still maintained that the American chestnut blight was not different specifically from E. gyrosa as found in Europe and America, but was merely a more luxuriant strain that had so developed through its parasitic habit. It is to be remembered, however, that all of the above investigators, except Shear, have based their conclusions merely on micro- scopic examination, since they have not had opportunity to study the situation in the field, and have not made cultures or inoculation experiments. On the other hand, it is to be taken * The conidial stage of the fungus described. fThe asco-stage of the fungus described. Fries apparently published his description before Schweinitz. $This fungus, according to von Hohnel (29). 426 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. into consideration that they are all botanists with a very extended experience in the systematic study of fungi. The Andersons have taken the other extreme, namely, that the chestnut blight, which they call Endothia parasitica, is entirely a distinct species from E. gyrosa, which they call E. virginiana. Their conclusion is evidently based on the para- sitic habit of the former as compared with the saprophytic habit of the latter, the difference between the two in artificial cultures, and the slight morphological differences in their ascospores. Pantanelli (53) in his recent article might be considered as agreeing with the Andersons in considering the two as distinct species, since in his conclusions he says: "The D lap or the parasitica Murrill is an Endothia, closely related to, but not like, the E. radicalis (Schw.) Fr. Hence it is oppor- tune to distinguish it as E. parasitica (Murr.) Anderson." However, Pantanelli was trying to show that these two were not entirely identical, and was not really concerned in their exact relationship, since he stated earlier in a footnote: "Recently, November 28, 1912, Professor P. A. Saecardo has communicated to me that he regards E. parasitica as a race of E. radicalis modified by parasitism. One may then consider whether it is a species or a distinct variety, but from the view- point of the pathologist it makes no difference." The writer, after a careful study of the blight fungus and of Endothia gyrosa, microscopically, in cultures, and in inocula- tion experiments, with an opportunity to examine both in the field, and also specimens of E. gyrosa on several hosts from Europe, has come to the conclusion that these two forms are too closely related to be considered distinct species. On the other hand, they are certainly distinguished through slight mor- phological differences in their ascospores, marked and constant cultural differences, and the apparently great difference in their parasitic tendencies. These differences lead us to consider the blight fungus as a distinct variety of E. gyrosa, which is evi- dently the older form from which the blight fungus has been derived. As previously stated, neither Endothia radicalis nor E. gyrosa and its variety parasitica differ enough in their fruiting pustules or conidial spores to present any very special distin- guishing characters. The ascospores of E. radicalis, however, CHESTNUT BARK DISEASE. 427 differ from both the latter by being decidedly narrower (see Plate XXVIII a-c). The ascospores of E. gyrosa are much nearer to the type of the true blight fungus than to E. radicalis, although they are somewhat intermediate. In general we can describe the ascospores of E. radicalis as linear, those of E. gyrosa as narrowly oval, and those of E. gyrosa var. parasitica as broadly oval. Usually one finds some spores of E. gyrosa and the variety parasitica that cannot be distinguished in size or shape. However, upon examining many from a specimen, one can tell which it is, as E. gyrosa has some spores that are narrower, and variety parasitica some that are broader, than any found in the other form. Measurements were made of one hundred aseospores of Endothia gyrosa var. parasitica from ten different chestnut trees from various localities, and these varied from 6 to 10 tt long x 275 to 5 n wide, while the average was 7.45 ^ long x 3.2 /* wide. Similarly, one hundred ascospores of E. gyrosa from ten dif- ferent chestnut trees from various localities, including one from Europe, varied from 6 to 9 /u, long x 2 to 3.5 /x wide, the average being 7.205 /A long x 2.695 it wide. To have maintained the same proportion in width as in length to var. parasitica, these spores should have been 3.095 /A wide. Likewise, sixty ascospores of E. gyrosa on six oak trees from different localities, one from Europe, showed a variation of 6-9 /x x 2-3.25 p, averaging 7.099 ^ x 2-733 P» Also forty ascospores of E. gyrosa on Carpinus from two sources in Europe varied from 5 to 10 p x 2.25-3.5 /<*, averag- ing 7.58 /* x 2.8 p. These .measurements show that there is a rather constant dif- ference in the width of the ascospores of Endothia gyrosa and E. gyrosa var. parasitica, no matter what the host or the locality from which they came, and if we also take into consideration the differences in artificial cultures and in the parasitic habits of the two, there seems no reason for not considering the blight fungus at least a distinct variety. The nomenclature of this variety is as follows: Endothia gyrosa var. parasitica (Murr.) Clint. Diaporthe parasitica Murr. Torreya 6 : 189. 1906. Valsonectria parasitica Rehm, Ann. Myc. 5:210. 1907. Endothia parasitica Anders. Phytop. 2 : 262. D. 1912. Endothia gyrosa var. parasitica Clint. Science 34:913. 27 D. 1912. 428 CONNECTICUT EXPERIMENT STATION REPORT, 1912. ARTIFICIAL CULTURES. Source of Cultures, etc. We have had cultures of Endothia gyrosa under observation for more than a year, and of the variety parasitica for more than four years. These have been obtained from many different localities, and from both chest- nut and oak in each case. For example, we now have eighteen different cultures of the chestnut blight obtained from localities in Massachusetts, Connecticut^ New York, Pennsylvania, and the District of Columbia ; and besides these we have had others from time to time. We have five cultures of the blight originally obtained from three different species of oak, from two regions in Connecticut and one in Pennsylvania. Of E. gyrosa on chest- nut we have fifteen cultures from eight different regions in Pennsylvania, Virginia, Tennessee, and North Carolina, and one from Europe; and ten cultures from three species of oak from five* different regions in the District of Columbia, Virginia, and North Carolina. We have grown many hundreds of these cultures on a variety of media in test tubes and Petrie dishes, though for most pur- poses tubes of potato- or oat- juice agar have proved the most satisfactory. From this extended experience we have been able to judge accurately as to purity of the cultures, constancy of their cultural characteristics, and differences that distinguish the variety from the species. Ordinarily the conidial spores of each have regularly appeared in these cultures, but in varying degree. In no case has the asco-stage of either been produced. Its production has seemed more likely to occur in the case of Endothia gyrosa, since in some cultures the conidial fruiting stage appeared as rather large, distinct, elevated pustules; but these have never shown any signs of ascospore formation. We have made some attempts, by special media or treatment, to induce the asco-stage to appear in these pustules, but without success. Endothia gyrosa versus var. parasitica. The following characteristic differences were noted in special test tube cultures made at the same time on potato-, Lima bean-, and oat- juice agar, from twenty-five sources of Endothia gyrosa and ten sources of var. parasitica. In general, it may be stated that the potato- juice agar favors spore production for both, while the CHESTNUT BARK DISEASE. 429 oat- juice agar favors a vigorous aerial mycelial development, especially for E. gyrosa. The bean-juice agar is somewhat intermediate in both respects. On any of these media, E. gyrosa is much less likely to exude spore masses in abundance than the variety parasitica. Perhaps this accounts for the ease with which the variety propagates itself in nature. The chief cultural differences of the two are as follows : (i) Var. parasitica fruits more abundantly, and exudes the sticky spore masses much more conspicuously, than does Endothia gyrosa. (2) The variety fruits earlier than the species, as determined by the exuding spore drops. (3) The variety has less evident, smaller, or more embedded fruiting bodies than the species, in which they are often elevated, distinct pustules, rarely hidden by the exuding spore mass. (4) The species develops a much more luxuriant aerial mycelium (except pos- sibly on potato agar) than does the variety. (5) The species has its aerial mycelium more generally and more highly orange col- ored, especially on oat- juice agar, than does the variety. The more minute and variable differences of the two on the three media are as follows: On the potato-juice agar var. parasitica forms chiefly an embedded growth, which, while white at first, soon becomes rather deeply colored, and produces numer- ous obscure or embedded fruiting bodies, which exude small, colored, sticky spore drops rather thickly over the surface of the agar. Finally, a slight surface growth of a flavus mycelium sometimes develops. The species differs in having at first a slightly more evident growth of mycelium, and finally having usually fewer, but larger, spore masses. The color of the em- bedded growth is variable, usually darker than in the variety, sometimes blackish, as if from bacterial contamination, but possibly due to variation in the composition of the medium. On the Lima bean- juice agar var. parasitica produces fewer, but larger, fruiting bodies and spore drops than on the potato- juice agar, while its aerial mycelium is more evident, and varies from albus to sulphureus in color. The species makes a much more evident aerial growth than the variety, while its fruiting pustules are decidedly fewer, larger, more elevated and distinct, and exude spores less abundantly. The color is much more evi- dent than in the variety, though variable even in the same tube, running from albus through sulphureus and flavus to even 43° CONNECTICUT EXPERIMENT STATION REPORT, IQI2. aurantiacus-miniatus on the edges where it is in contact with glass or medium. On oat- juice agar the variety parasitica forms a somewhat more evident aerial mycelium, but has fewer pustules and less evident spore drops even than on the Lima bean- juice agar. It usually has a deeper color, which varies from albus to luteus. The species on oat-juice agar forms a very luxuriant growth, even more so than on Lima, bean- juice agar, and though its fruiting bodies are not so numerous, they are often evident exposed pustules, only partially hidden by the spores mass, which exudes with difficulty. The color assumes its maximum develop- ment and is in strong contrast to that of the variety on the same medium. It is usually more uniform and intense in color than on the bean-juice agar, finally varying from luteus through aurantiacus to miniatus and even badius when in contact with the glass or medium. Part of the growth, especially on the upper edge, however, often remains albus. The color of the spore masses of both forms varies in dif- ferent cultures from sulphureus to nearly purpureus, depending apparently on age, variation of the medium, bacterial contamina- tion, or other unknown factors. Likewise, a culture when renewed on the same medium sometimes acts somewhat differ- ently for some unknown reason, as to luxuriance in mycelial growth or spore development, or color characters. Tannic Acid in Cultures. Since tannin is found in such large quantities in the wood of chestnut, and since this varies accord- ing to the age of the tree, etc., it has been suggested previously in this paper that this variation may have some bearing upon the development of the chestnut blight. It was thought desir- able, therefore, to study both the saprophytic Endothia gyrosa and the variety parasitica in artificial cultures containing dif- ferent percentages of tannic acid (M. C. W. brand, U. S. P.) to determine how this affected their vigor, growth and spore production. These cultures have all been made by Mr. Stoddard under the writer's direction, and the data here given should be credited to both investigators. We have used mainly for this work two rather recent cultures of E. gyrosa on two species of oak from Washington, D. C., and four cultures of E. gyrosa var. parasitica on chestnut, two from Washington and two from CHESTNUT BARK DISEASE. 431 Per cent, of Tannin. Result. Endothia gyrosa Quercus sp. Endothia gyrosa Quercus velutina. E. gyrosa var. parasitica Castanea dentata. E. gyrosa var. parasitica Castanea dentata. i E. gyrosa var. parasitica Castanea dentata. E. gyrosa var. parasitica Castanea dentata. 4# Grew... Failed.. 5 3 8 0 8 0 8 o 7 i 5 3 4- 8$ Grew . . . Failed.. 6 2 6 2 7 i 8 o 7 i 7 i v Grew. . . Failed . . 7 i 5 3 5 3 7 i 8 0 7 i 8* Grew... Failed.. 4 4 4 4 Q 2 4 4 4 4 4 4 ,0, Grew. . . Failed.. 0 8 2 6 3 5 3 5 4 4 6 2 10.5$ Grew. . . Failed.. i 7 o 8 6 2 4 4 5 3 5 3 II* Grew. . . Failed.. 2 6 i 7 8 o 4 4 5 3 3 5 ii. 5* Grew. . . Failed.. i 7 i 7 5 3 5 3 4 4 5 3 12$ Grew . . . Failed.. 2 6 2 6 5 3 6 2 5 3 5 3 14$ Grew. . . Failed.. o 8 o 8 i 7 O 8 o 8 o 8 Total No. Grew. . . Failed.. 28 52 29 51 56 24 49 31 49 31 48 32 Total Grew... Failed.. 35$ 64$ 30$ 39$ 61$ 39$ 40$ Connecticut. Of these four, three had been in culture only a few months, while one had been in culture over three years. In each test we made three cultures of each of the above for duplication. We grew these on plain potato- juice agar, as checks for comparison, and also on this medium to which had been added the following percentages of tannic acid: 0.2, 0.4, 0.8, 1.2, 1.6, 2.4, 3.2, 4.0, 4.8, 6.0, 8.0, 10.0, 10.5, n.o, 11.5, 12.0, 14.0 ; see Plate XXVII. These cultures were first made in 1912, and repeated in 1913 for confirmation, this time using five cul- tures of each in each test. The table shows the results of all these cultures in the tubes containing 4% or more of tannic acid. Those containing lower per cents, all grew, and so are omitted in the table. From the results of these investigations we obtained the following information: % (i) The growth of either fungus causes no darkening of the plain potato- juice agar, but when tannic acid is added, even as 432 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. low as 0.2 per cent, in case of var. parasitica, the growth of the fungus causes a darkening of the medium. This indicates an oxidation of the tannic acid by the fungus, since these tubes without the introduction of the fungus remain undarkened except with the higher percentages, when they color as soon as made, upon cooling. With E. gyrosa, this darkening scarcely takes place, and with var. parasitica is less evident in those tubes containing only 0.2 anc| 0.4 per cent, of tannic acid, but shows on all strengths above these with both fungi about the same, though appearing sooner with var. parasitica. (2) The medium in the tannic acid tubes remains liquefied when 0.8 per cent, or more tannic acid is added. The acidity of potato- juice agar and, in the lower percentages, of tannic acid potato- juice agar, where darkening of the medium does not interfere, can be tested before and after growth of these fungi AT by titrating with — Na O H, using phenolphthalein as an indi- cator. These tests show that after E. gyrosa or var. parasitica has fully developed in plain potato- juice agar the acidity is practically unchanged; but in tannic acid potato- juice agar both of these fungi cause a lowering in the acidity of the medium, and the higher the acidity usually the greater the loss, though not proportionately greater, as shown by the following tests : Tannic Acid Acid Test Acid Test Loss in added (per cent.). before inoculation. after growth. Acidity. N N o.o 0.15 cc. — Na O H 0.15 cc. — Na O H o.o 20 20 0.2 •9 0.4 1.2 < « tt < < i « < « 0.8 1.8 <« « « « «< 1.2 2.1 « « < < < < i < 1.6 2.7 «« « « « « 0.4 0.5 0.85 " " " " " 0.35 1.4 " " " " " 0.7 1.8 " " " " " 0.9 (3) Cultures of E. gyrosa var. parasitica containing 0.2, 0.4, 0.8 per cent, tannic acid show a more vigorous spore develop- ment than the check cultures of potato- juice agar without tannic acid. The same was true of E. gyrosa regarding mycelial development, but to a less extent, and possibly also as to spore development, though with this fungus the spores do not exude very abundantly in any case. (4) At about 4 per cent, the loss in color, especially with E. gyrosa, becomes quite evident. In the liquefied tubes up to CHESTNUT BARK DISEASE. 433 4 per cent, tannic acid, the growth of the fungi tends to form a more or less firm coating over the surface, after the manner of growth on the solid medium. Above 4 per cent, the growth becomes gradually less evident, generally showing in floating patches, embedded masses, or lateral growths around the side of the glass. Finally, at the highest percentages, 10 to 14, growth entirely ceases, only one having been successful at the latter strength in any of the tubes. (5) In the higher percentages of tannic acid E. gyrosa shows an enfeebled growth sooner than does var. parasitica, since at 6 to 8 per cent, it makes comparatively little growth, correspond- ing to that made by the variety at about 10 per cent. It gen- erally fails entirely to make any growth at above 10 per cent., or only a poor growth above 8 per cent, in most of the tubes; while the variety in only one case made any growth above 12 per cent, and rarely any but a poor growth above 10 per cent. (6) At the higher percentages the difference in the appear- ance of the two fungi is less marked than at the lower, so that from 4 per cent, up, where spore production of the variety is largely cut out, they are scarcely to be distinguished. (7) There was some variation in development with the dif- ferent cultures of the same fungus in the higher percentages of the tannic acid, as shown by one of the cultures of var. par- asitica from Connecticut which had been in artificial culture for over three years failing to grow quite as well as the more recent cultures. These variations are perhaps not constant. (8) All the preceding notes relate to cultures that were inoc- ulated from plain potato- juice agar directly onto those contain- ing various percentages of tannic acid. Another set of cultures was made in which each was brought up gradually through all the lower percentages of tannic acid. In these it was found that this gradual acclimatization to the tannic acid gave a somewhat more luxuriant growth of both fungi at the higher percentages than when transferred directly from the potato- juice agar to these. Later experiments based on the preceding results were made with all our cultures of E. gyrosa (26 in number) and those of var. parasitica (22 in number), using two cultures of each and the following percentages of tannic acid: 4.0, 6.0, 8.0, 10.0. These cultures showed, as in the previous tests, that the variety 434 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. parasitica will grow in higher per cents, of tannic acid and give a more evident development of mycelium than E. gyrosa. The details of this experiment are given in the appended table. Per cent, of i Tannin. Name. Grew. Total. Failed. iS I 29 1 15 23 10 2 je. j=* V. si >i/5 o fc fe g SH 0 o £ £<= 4* Endothia gyrosa. ... 0 o 2 0 0 O ~4~ 0 31 43 59-6 97.6 21 I 40.4 2.4 E. gyrosa var. parasitica 6£ Endothia gvrosa 15 13 9 3 31 44 59-6 100. 0 21 O 40.4 0.0 E. gyrosa var. parasitica 8# Endothia gyrosa 0 15 0 ! 2 o 14 0 15 9 _5_ 0 8 13 3 20 13 7 0 ~6~ o 29 37 '55-7 84.1 23 7 44-3 15-9 E gyrosa var parasitica 10% Endothia gyrosa. 26 38 50.0 86.3 26 Q 50.0 13-7 Endothia gyrosa var. parasitica INOCULATION EXPERIMENTS. General Conditions, etc. These experiments were undertaken primarily to determine the parasitic tendency of Endothia gyrosa as compared with that of the variety parasitica. That the latter could produce cankers when inoculated into chestnuts had been abundantly proved by the work of Murrill and others. With most of our inoculations both the species and the variety were used at the same time, and checks were also included. Nearly all these inoculations were made from artificial cultures, and usually only with conidial spores. Ordinarily a small slit in the bark was made with a sharp scalpel, spores from the cultures were introduced on a needle, the wound covered with moist cotton, and then bound with paraffine paper or bicycle tape. After several weeks the covering was removed. The checks were treated in the same way, except that no spores were intro- duced into the wound. In this way there were inoculated two- to three-year-old seedling chestnuts, four- or five-year-old chestnut sprouts, and two-year seedling oak at the Station Farm at Mount Carmel; six- to eight-year-old slow-growing chestnut seedlings at the Station forestry plantation at Rainbow; and two- to four-year- old oak sprouts in a waste lot at Highwood. The tables which follow give the data for all inoculations, since there are factors CHESTNUT BARK DISEASE. 435 that apparently enter into their success that we had not in mind when the experiments were undertaken, namely: — length of time the fungus has been in artificial cultivation, age of the particular spores used, and time of year of the inoculation. This makes it difficult to judge of the results of certain of these inoculations, since two or more of these factors may have been involved. The final results of our inoculations were determined about the second week in October. Of course this gave some of the earlier inoculations made in May a much longer time to develop than those made in July, although these latter had plenty of time to show whether or not they were successful. We will consider the results briefly under the following headings. Endothia gyrosa versus var. parasitica. Ordinarily it takes about a month to determine whether or not an inoculation has taken, and even then it is sometimes doubtful, since the tissues around the wound often die back for a short distance as the result of the mechanical injury. The sum total of our experi- ments brings out quite clearly the difference in the parasitic nature of these two fungi. For instance, 151 out of all of our 324 inoculations with var. parasitica, from all sources on all hosts, produced more or less evident cankers, that is, 47 per cent, were successful; while of the 148 similar inoculations with E. gyrosa only 2 took, or about I per cent. Of these two, one showed only a comparatively small dead area, with fruiting pustules, around the point of inoculation, but did not seem to continue its growth, while the other was on a dead seedling whose roots had been cut off by mice, which no doubt weakened it, allowing the fungus to make an excellent growth, and even to produce its ascospores. If we take into consideration only our inoculations of var. parasitica originally obtained from chestnut and inoculated into chestnut sprouts and seedlings, we find that out of 232 inoculations 132, or 57 per cent., took, as compared with entire failure of E. gyrosa under the same con- ditions. None of the 228 check trees in all our experiments showed any signs of infection, thus proving that the wounding alone was not harmful when protected from infection. With the check trees the cutting usually killed a little bark on either side, especially if the knife was run under between the bark and the wood. This never grew larger, and the callus of new tissue formed in the wound was always healthy. With 436 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. the wounds inoculated with E. gyrosa, sometimes this injured bark was a little more extensive than with the checks, which indicated a slight but futile attempt at parasitism. Occasionally, on this dead bark and exposed wood, a slight fruiting growth of the fungus as a saprophyte was formed. With var. parasitica, however, the bark was gradually killed in an increasing area surrounding the point of inoculation, and this had a more or less irregular outline, spreading faster in some directions than in otners. Eventually the whole stem or limb was encircled, if the inoculation was made early in the season (see Plate XXV a). At the inoculation point a callus of young tissue often developed, and the vitality of this was greater than that of the older tissues, since it often remained healthy, until, being entirely surrounded by dead tissues, it died as much from adverse nutritive conditions as from the direct action of the fungus (Plate XXV b). After the cankers attained some size, their reddish dead bark often became cracked, and the Cytospora fruiting stage appeared in more or less abundance. An examination of the inoculations as late as the last of December, however, failed to show that the asco-stage had developed on any of them. Whether this means that ordinarily the mature fruiting stage does not appear until the second season, we do not know, but it shows that sometimes this is the case. The inoculations made early in May on the chestnut sprouts one to two inches in diameter entirely girdled these for six to eight inches, forming very evident cankers, but not always with a conspicuous develop- ment of conidial spores. Hosts Inoculated. In the inoculation tests we used seedlings and sprouts of both chestnuts and oaks. Considering first only the chestnut hosts, we found that, as a rule, the variety para- sitica could be more easily inoculated into the sprouts than into the seedlings, and that on the sprouts the blight made a larger growth in the same length of time. This greater development might in part be due to the larger size of the sprouts, which varied from about one-half to one and one-half inches in diameter, while the seedlings were only about one-quarter to three-quarters of an inch in diameter. Out of a total of 177 inoculations with cultures originally from chestnut made on chestnut seedlings, 91, or 51 per cent., took, as compared with CHESTNUT BARK DISEASE. 437 41 successful out of a total of 55, or 75 per cent., on the sprouts. An attempt to inoculate a young Japanese chestnut six inches in diameter failed entirely, although sixteen inoculations were made at two different periods. This seems to show that the tree had great resistance, if not immunity, to the disease. As regards inoculation of chestnut, versus oaks, it was found that the former were much more readily infected than the latter, which showed only 12 successful infections out of 51, or 23 per cent. All of these were confined to the sprouts, and did not make nearly so vigorous growth as did the inoculations on chestnut sprouts. The oak seedlings used were rather small, and the inoculations were made comparatively late, using cultures obtained originally from both oak and chestnut. Source of Cultures. Most of our inoculations were made with cultures obtained from chestnut, as at the time we had only one culture of var. parasitica from oak, namely Quercus velutina from Woodmont, Pa. This was inoculated into both chestnut and oak seedlings and sprouts. The inoculations into chestnut seedlings showed 4 successful out of 25, or about 15 per cent., while the 16 made on the chestnut sprouts all apparently failed, for some not very evident reason, possibly because made in July with old spores. Of the 20 inoculations on oak seedlings, all failed, while of the 12 on oak sprouts, 5, or 42 per cent., took more or less vigorously. From the results of the inoculations with this single culture, it would seem that the strain from oak at least was not quite so active a parasite as that from the chestnut itself. Whether or not cultures from chestnuts from different regions, or from living as compared with dead trees, show any difference in virulence, we are not certain. In our experiments we did not get any conclusive results along this line. To determine these points accurately, however, one would need cultures that id only recently been obtained from their hosts, and whose spores when used were comparatively young and of the same ige. Age of Cultures. It seems quite probable that the longer the variety parasitica is kept in culture the mere likely it is to lose, it least in part, its virulence. While no direct experiments were lade to determine this point, it is possibly shown by the cul- tures obtained originally from a Japanese chestnut in Westville 27 438 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. OOIOMOWOO O O O O 0 0 O O O co O O NMOOMOOOOOOOO •jnjjqnop jqnop •^J3A OOOO«OOOOOO O O O O O O "-"OOOOOOOMOOOO O O"> O M XT) O Mcoxnor-OO oooooo OOOOOO Thu^QTOO OOOOOOOOOOOOO NOO OOcoooOOr^OOC>OOOOO O O 6 OCOCOCOCOOO m o O m m O mOmOOOOOOOmOO a. ex ex a rt ri rt rt OH d. OH CU Is. 0) 0) 0) (t) O^ oo . oo . 1! \n \n vn xn N O 22^8^! a, c, <« en co co CO N rt rt MM M CXCX " I P V *** 75g6. E.radicalis. 7590,7584. E. gyrosa. 7582,7581. E. gyrosa var. parasitica. PETRIE DISH CULTURES OF THREE AMERICAN ENDOTHIAS. PLATE XXVII a-l. E. gyrosa first in each case, on following per cents.: a, o; b, .2; c, .4; d, .8; e, 1.2; f, 1.6; g, 2.4; h, 3.2; i, 4.; j, 4.8; k, 6.; 1, 10. TANNIC ACID CULTURES OF ENDOTHIA GYROSA AND VAR. PARASITICA, p. 430. PLATE XXVIII. a, d, g. E. radicalis. b, e, h, j. E. gyrosa. c, f, i, k. E, gyrosa var. parasitica, p. 367. a-c. ascospores ; d-f. spores in ascus ; g-i. conidial spores ; j-k. isolated perithecia, k. showing mycelium from germinating ascospores within. SPORE STAGES OF THREE AMERICAN ENDOTHIAS. FEBRUARY, 1916 BULLETIN 371 CORNELL UNIVERSITY AGRICULTURAL EXPERIMENT STATION OF THE NEW YORK STATE COLLEGE OF AGRICULTURE BEVERLY T. GALLOWAY, Director Department of Plant Pathology THE LEAF BLOTCH OF HORSE-CHESTNUT V. B. STEWART FORESTRY COLLEGE or A AGniCULTUKC UNIVCKStTY OF CALIFORNIA PUBLISHED BY THE UNIVERSITY ITHACA. NEW YORK CORNELL UNIVERSITY AGRICULTURAL EXPERIMENT STATION EXPERIMENTING STAFF • BEVERLY T. GALLOWAY, B.Agr.Sc., LL.D., Director. HENRY H. WING, M.S. in Agr., Animal Husbandry. T. LYTTLETON LYON, Ph.D., Soil Technology. JOHN L. STONE, B.Agr., Farm Practice. JAMES E. RICE, B.S.A., Poultry Husbandry. GEORGE W. CAVANAUGH, B.S., Agricultural Chemistry. HERBERT H. WHETZEL, M.A., Plant Pathology. ELMER O. FIPPIN, B.S.A., Soil Technology. G. F. WARREN, Ph.D., Farm Management. WILLIAM A. STOCKING, JR., M.S.A., Dairy Industry. WILFORD M. WILSON, M.D., Meteorology. RALPH S. HOSMER, B.A.S., M.F., Forestry-. JAMES G. NEEDHAM, Ph.D., Entomology and Limnology. ROLLINS A. EMERSON, D.Sc., Plant Breeding. HARRY H. LOVE, Ph.D., Plant Breeding. ARTHUR W. GILBERT, Ph.D., Plant Breeding. DONALD REDDICK, Ph.D., Plant Pathology. EDWARD G. MONTGOMERY, M.A., Farm Crops. WILLIAM A. RILEY, Ph.D., Entomology. MERRITT W. HARPER, M.S., Animal Husbandry. JAMES A. BIZZELL, Ph.D., Soil Technology. GLENN W. HERRICK, B.S.A., Economic Entomology. HOWARD W. RILEY, M.E., Farm Mechanics. CYRUS R. CROSBY, A.B., Entomology. HAROLD E. ROSS, M.S.A., Dairy Industry. KARL McK. WIEGAND, Ph.D., 'Botany. ' EDWARD A. WHITE, B.S., Floriculture. WILLIAM H. CHANDLER, Ph.D., Pomology. ELMER S. SAVAGE, M.S.A., Ph.D., Animal Husbandry. LEWIS KNUDSON, Ph.D., Plant Physiology. KENNETH C. LIVERMORE, Ph.D., Farm Management. ALVIN C. BEAL, Ph.D., Floriculture. MORTIER F. BARRUS, Ph.D., Plant Pathology. CLYDE H. MYERS, M.S., Ph.D., Plant Breeding. GEORGE W. TAILBY, JR., B.S.A., Superintendent of Livestock EDWARD S. GUTHRIE, M.S. in Agr., Ph.D., Dairy Industry. JAMES C. BRADLEY, Ph.D., Entomology. PAUL WORK, B.S., A.B., Vegetable Gardening. JOHN BENTLEY, JR., B.S., M.F., Forestry. EARL W. BENJAMIN, Ph.D., Poultry Husbandry. EMMONS W. LELAND, B.S.A., Soil Technology. CHARLES T. GREGORY, Ph.D., Plant Pathology. WALTER W. FISK, M.S. in Agr., Dairy Industry. ARTHUR L. THOMPSON, Ph.D., Farm Management. ROBERT MATHESON, Ph.D., Entomology. HORACE M. PICKERILL, B.S. in Agr.. Dairy Industry. MORTIMER D. LEONARD, B.S., Entomology. FRANK E. RICE, Ph.D., Agricultural Chemistry. VERN B. STEWART, Ph.D., Plant Pathology. IVAN C. JAGGER, M.S. in Agr., Plant Pathology (In cooperation with Rochester University). CHARLES H. HADLEY, B.S., Entomology. DANIEL S. FOX, B.S., Farm Management. WILLIAM I. MYERS, B.S., Farm Management. LEW E. HARVEY, B.S., Farm Management. BRISTOW ADAMS, B.A., Editor. LELA G. GROSS, Assistant Editor. The regular bulletins of the Station are sent free on request to residents of New York State. 410 BULLETIN 371 FORESTRY COLLEGt OF 1 AGRICULTURE UNIVERSITY OF CAUFO«NIA PLATE X LEAF BLOTCH OF HORSE-CHESTNUT THE LEAF BLOTCH DISEASE OF HORSE-CHESTNUT V. B. STEWART The horse-chestnut (/Esculus hippocastanum) is common throughout the State of New York. In public parks and private plantings the large, magnificent trees, with their deep green foliage, are particularly attrac- tive. Ordinarily they are not considered desirable for street trees, how- ever, owing to the excessive water supply that they demand; but in certain localities they have, been used extensively for street planting, and in many cities the species is very prevalent. There is some objection to the horse-chestnut because of the frequent yellowing and dying of the foliage during the summer. On trees that have received but little attention, the foliage is in many cases so dense that the inner leaves die and fall to the ground for lack of sunshine. It is believed, however, that a large proportion of the yellowing and sub- sequent death of the foliage may be attributed to leaf blotch, which is the most important disease affecting the horse-chestnut (ALsculus hippo- castanum) and the Ohio buckeye (AL. glabra). Leaf blotch is known in America and in Europe, apparently occurring, to some extent at least, wherever the horse-chestnut or allied species are found. It is not observed so commonly in northern Europe as in southern Europe, and apparently is never so destructive in these regions as in America. In the eastern part of the United States, where the horse- chestnut has a wide distribution, the disease is frequently observed, and in many cases a large proportion of the foliage on mature trees is affected. In nursery plantings leaf blotch is particularly destructive. In many cases the seedlings are completely defoliated by midsummer, and as a consequence their growth is greatly retarded. When the disease has once become established in a block of young nursery trees it usually causes considerable damage each year. The affected trees develop more slowly than they would normally, and a longer period of time is therefore required for them to attain a marketable size. Several plantings from seed have been observed which had made practically no increase in size for three seasons, due to the abundant occurrence of the leaf blotch disease each year. Not only does premature defoliation check the growth of the young trees, but apparently the trees affected are less able to withstand the adverse conditions of the subsequent winter months. An injury and dying back of the twigs and branches has been observed on trees that were badly diseased the preceding summer. 411 412 BULLETIN 371 The plantings of horse-chestnut in the nurseries of the State are relatively large, owing to the persistent annual demand for this stock. As a rule, however, nurserymen have not been successful in propagating the trees from seed because of the severe injury to the foliage caused by leaf blotch. This failure has resulted in annual importations of horse- chestnut trees from foreign countries. The trees obtained from Europe are three or four years old. They are planted in the nurseries of this country, where they are allowed to grow for one or two years longer before they are placed on the market. This method naturally involves considerable expense, requiring the nurserymen to charge a higher price for their stock than for trees successfully grown from seed in this country. Without question horse-chestnut trees protected from the leaf blotch disease can be propagated from seed at a much lower cost than that paid for imported stock. SYMPTOMS The leaves, and occasionally the petioles, are affected. The writer has observed lesions also on immature fruits, which were undoubtedly another type of the leaf blotch disease. The first indication of the disease on the foliage is a slight discoloration. As the lesion increases in size it becomes more or less irregular in outline and the newly invaded tissues appear water-soaked. Gradually the central part of the lesion becomes from dark red to brown in color, while the margin shows a yellowish discoloration blending into the green of the healthy tissue. The discolored area finally becomes dried and dies. The spots may be small, or they may involve a large part of the leaf surface and thus cause the dead area to curl (see frontispiece). Minute black specks may generally be seen, scattered separately over the lesion, and in some cases these appear before the tissue is completely dried out. In many cases these specks are crowded together in a definite area, which may be slightly lighter in color than the remainder of the affected tissue. The lesions on the petioles appear in the form of small reddish brown spots, which are usually somewhat longer than wide and extend up and down the petiole. The effects of the disease on the petiole are never very serious. The spots on the fruit are similar to those on the petioles, but there is no decay of the fruit tissue. • The striking symptom of the leaf blotch disease, however, is the dark red or brown color of the lesions, which often involve large areas or even the entire leaf. When the disease is very prevalent, especially in nursery plantings, the foliage appears as if it had been burned over by fire. THE LEAF BLOTCH DISEASE OF HORSE-CHESTNUT 413 CAUSE OF THE DISEASE Leaf blotch is caused by a fungous pathogene, Guignardia ALsculi (Peck) Stewart. This parasite obtains its food and nourishment by means of minute vegetative, root-like strands, called mycelium, which penetrate the leaves of the horse-chestnut and kill the tissues invaded. LIFE HISTORY With the presence of the fungus in the leaf, the mycelium extends in all directions and kills the surrounding tissues, producing the character- istic leaf blotch lesions. Soon gnarls of the mycelial threads appear at various points near the upper surface of the leaf, and these result in the forma- tion of fruiting bodies of the fungus. These fruiting bodies are known as pycnidia (Fig. 85), and are the character- istic minute specks already mentioned as appearing on the upper surface of the affected area. Within the pycnidium are borne a large number of spores, which are extruded from the opening in the top of the pycnidium. The spores, being very minute, are easily carried to other leaves by wind and rain, and are thus dis- seminated to a con- siderable distance. Falling on a leaf, the spore germinates, if moisture is present, by sending out a slender germ tube (Fig. 86, A), which grows into the tissue of the leaf and develops a mycelium with many branches, causing a disorganiza- tion and killing of the tissue in the affected area. When a number of spores infect the same leaf, a large part or all of the tissue becomes affected and the leaf is no longer able to function in the manufacture of food for the tree. FlG. 85. CROSS SECTION OF A HORSE-CHESTNUT LEAF THROUGH A PYCNIDIUM OF THE FUNGUS (MUCH MAGNIFIED) The spores are shown inside the pycnidium. They escape through the opening in the top FlG. 86. SPORE FORMS OF THE LEAF BLOTCH FUNGUS A, pycnospores, some of which have germinated; B, ascus, containing eight ascospores; C, ascospores, some of which have germinated 414 BULLETIN 371 As the season advances the disease becomes more prevalent with each period of wet weather, and, on nursery trees especially, a large part of the foliage may be killed by midsummer. The fungus lives over winter in the old diseased leaves that fall to the ground. During the winter there are formed on these fallen leaves special fruiting bodies, known as perithecia (Fig. 87), which become mature about the time when the trees develop the first new leaves in the spring. Within the perithecium are numerous sac-like bodies, known as asci (Fig. 86, B), containing spores which escape through the opening in the top of the perithecium. These ascospores (Fig. 86, c), being very minute, are carried by the wind or by spattering drops of rain to the new foliage, where they produce the first infections of the year. From ten to fifteen days later the characteristic leaf blotch le- sions begin to appear, and soon pycnidia are formed which are a source of further distribution of the fungus. vSmall trees in the nursery, on which the foliage is near the ground, often show numer- ous spots early in the spring. This is due to the fact that Proportion of the of the winter Stage (perithecia) are able to reach the newlv developed leaVCS and produce infections during periods of damp, cloudy weather. In mature trees the chances that the spores may reach the newly developed foliage from the perithecia in old leaves on the ground are usually limited, but at least a few leaves generally become infected in this manner, and the pycnidia with spores, which develop in the lesions, are the source of new infections whenever conditions are favorable. When there is but little rainfall throughout the summer, very few spores find suitable conditions for germination and thus but little of the foliage is attacked. For this reason the disease may be more prevalent in certain years than in others. CONTROL In determining control methods for a fungous disease it is necessary to consider the relation existing between the host and the parasite that causes the disease. In general, in the case of leaf blotch of horse-chestnut, weather conditions that influence the trees affect also, to some extent, FIG. 87. CROSS SECTION OF A HORSE-CHESTNUT LEAF THROUGH A PERITHECIUM (MUCH MAG- SpOrCS shows the sac-uke bod.es (asci) with ascosporcs. In early spring the spores escape through the opening in the top of the perithecium THE LEAF BLOTCH DISEASE OF HORSE-CHESTNUT 4i5 the activities of the fungus. Rainy periods throughout the summer favor the growth of the trees, since sufficient moisture is supplied for their development. On the other hand, wet weather also affords the necessary conditions for the pathogene. With the presence of moisture the fungus spores are able to germinate and produce infections when they fall on the leaves of the trees. For the control of the leaf blotch disease, therefore, it is necessary to check the attack before suitable conditions FlG. 88. A HAND DUSTING MACHINE This duster is suitable for dusting small trees are afforded for the germination of the spores on healthy foliage. It is impossible to check the activities of the parasite in the affected leaf after the spores have germinated and the germ tubes have gained an entrance into the leaf tissue. As previously stated, the first infections in the spring are produced by spores from the perithecia in old dead leaves on the ground. Un- doubtedly much damage can be prevented by plowing under or burning the old leaves before the new foliage is developed. A large proportion 416 BULLETIN 371 of the perithecia are thus destroyed and the source of early infections is to a considerable extent eliminated. On the other hand, this treatment is not sufficient to completely control the disease, for usually enough old leaves remain scattered about to enable the fungus to gain a foot- hold on the new leaves. In order to forestall these attacks of the fungus and subsequent in- fections by spores from the pycnidia, the leaf surface must be covered with a fungicide that is poisonous to the parasite. When the spore germinates, the germ tube comes in contact with the fungicide and is FlG. 89. A POWER DUSTING OUTFIT This machine is suitable for dusting large trees killed, and thus its entrance into the tissues of the leaf is prevented. The fungicide does not penetrate the leaf and kill the mycelium, and since the spores are very minute- — being about y*W of an inch in diameter — the fungicide must be applied so that it completely covers all parts of the leaves. The applications must be made at such intervals as will afford the greatest amount of protection throughout the summer. The proper time for the first application, especially for nursery stock, is soon after the buds open in the spring. This should be followed by at least two other treatments, made at intervals of from two to three weeks. In rainy seasons it is advisable in many cases to make one or THE LEAF BLOTCH DISEASE OF HORSE-CHESTNUT 417 two additional applications in order that the foliage will be thoroughly covered with the fungicide at all times. Lime-sulfur solution (one gallon to fifty gallons of water) or bordeaux mixture may be used for controlling the disease. Considerable difficulty has been experienced, however, in the use of these spraying mixtures owing to the dense foliage of horse-chestnut trees. In the attempt to cover thoroughly all parts of the foliage, the trees are often drenched with the spray solution, and when lime-sulfur solution is used severe burning of the leaves may result. In the summer of 1915 an experiment was made on nursery trees for the control of leaf blotch by dusting. The dust mixture used contained ninety parts of finely ground sulfur L and ten parts of powdered arsenate of lead.2 This mixture proved as effective as lime-sulfur solution in controlling the disease. On trees that were not treated, practically fifty-nine per cent of the leaves were diseased; while only three per cent of the leaves on the trees that were dusted showed in- fections, and the trees sprayed with lime-sulfur solution 1-50 had ten per cent of the foliage diseased In comparing the results on the sprayed and the dusted trees, it is believed the lime-sulfur spray was the less effective mainly because of the density of the foliage. The spray was applied with a hand sprayer which lacked sufficient power to furnish the driving spray necessary to thoroughly cover all parts of the foliage, while, on the other hand, the cloud of finely ground dust mixture floated through the trees and settled on the leaves, completely covering them and thus affording better protection. The dust mixture was applied with a hand machine, illustrated in figure 88. This duster is very satisfactory for treating small shade DUSTING SHADE TREES 1 The sulfur was so finely ground that at least 95 per cent would pass through a 20O-mesh sieve. The method of testing sulfur is described by F. M. Btodgett in Bulletin 328 of this experiment station. 2 The lead arsenate was added primarily for its adhesive properties. On being moistened there is a tendency for it to become somewhat gelatinous and sticky, and this increases the adhesiveness of the mixture. Lead arsenate is effective also in controlling insects that chew the foliage. In the case of horse-chestnuts, however, which are seldom attacked by insects, finely ground gypsum, a much less ex- pensive substance, may be substituted for lead arsenate. BULLETIN 371 trees or for use in small plantings of nursery stock. For dusting on a more extensive scale a power machine, such as is illustrated in figures HOTOGRAPH BY F. M. BLODGETT FlG. 91. A TRACTION DUSTING MACHINE This duster is suitable for treating nursery stock 89 and 90, is preferable. The outfit shown has been used successfully for dusting orchard trees. The machine is operated by a gasoline engine, and the cloud of dust mixture, which is discharged from the long pipe, PHOTOGRAPH BY F. M. BLODGETT FlG. 92. TRACTION DUSTING MACHINE IN OPERATION floats through the trees and completely covers all the foliage. The machine is suitable also for dusting shade or park trees. THE LEAF BLOTCH DISEASE OF HORSE-CHESTNUT 419 For treating large plantings of horse-chestnut trees in the nursery, a traction duster such as is illustrated in figures 91 and 92 is desirable. The machine is especially light in weight and runs between the rows, the dust being discharged from the two pipes in the rear. One man and a horse are all that is required to operate this machine. Although spraying is effective in controlling leaf blotch, the dust method is preferable, as there is less danger of injuring the foliage by burning; further, the dust mixture can be applied more thoroughly and with greater facility than the spraying solution. The dust mixture is somewhat more expensive than the spraying solution, but ;ts greater cost is offset by the consequent saving in time and labor. UNITED STATES DEPARTMENT OF AGRICULTURE BULLETIN No. 275 Contribution from the Bureau of Plant Industry WM. A. TAYLOR, Chief Washington, D. C. PROFESSIONAL PAPER. AprU 7, 1916 FOREST PATHOLOGY IN FOREST REGULATION. By E. P. MEINECKE, Forest Pathologist, Office of Investigations in Forest Pathology. CONTENTS. Introduction Page. 1 Metho Regulation of yield 2 Lc Working plans 2 Ta Rotation 6 Co Cutting cvcle 8 In1 Cumulative risk 9 Conclu Period of transition 15 De Condition of timber stock 16 Fo Total loss 16 Inferior species 19 Methods of investigation 22 Choice of species and site 22 Field methods . . 23 Pathology of white fir 27 Description of areas 33 On Page. Methods of investigation— Continued. Local pathology of white fir 35 Tabulation of data Condensation of data Interpretation elusions and outlook Decay in relation to wounds Forest regulation Care of virgin forests Forest regulation through timber sales Marking Pathological rotation and cutting cycles INTRODUCTION. At the time of the creation of the national forests in the United States the Government very suddenly found itself confronted with the problem of organizing an enormous acreage of practically virgin timber. It was natural that American forestry turned to the expe- rience of the Old World for guidance in this huge task; it was quite as natural that the present state of European forestry should have served as the ideal to be reached in the shortest time possible. In organizing the administrative machinery, European precedent could be followed more or less closely, but not so in almost all other phases of forestry. Except for certain economic factors and the develop- ment of modern machinery, conditions influencing the lumber industry in the United States are very dissimilar to those in the typical forest countries of central Europe. Our virgin forests them- NOTE.— This bulletin discusses the bearing of modern forest pathology on forest regulation. 98035°— Bull. 275—16 1 2 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. selves, and consequently the timber for sale, are more or less in the condition of European forests of several hundred years ago. The administration found itself then in the position of a man forced to take over not only an obsolete factory producing at random arti- cles of daily necessity in enormous quantities without having any control whatever over the quality turned out, but also a huge stock of products of all kinds and all values. Modern sales methods alone can not make the product any better, and the sudden adoption of modern methods of efficiency in the manufacturing end of the business would soon disorganize tl^e entire factory. It is clear that in the most important branch of forestry, silvi- culture, the blind adoption of European methods must encounter serious difficulties. Perhaps we are too prone to look upon Euro- pean forestry as a science worked out in all its details, the results of which are universally accepted as definitely settled. Critical perusal of modern European forestry literature shows an entirely different state of affairs. Even in Germany many of the funda- mental problems of forest organization are steadily discussed and are far from being considered as settled. Furthermore, what Gaskill 1 said 11 years ago is true to-day, namely, that " European foresters have not developed a true system or science of silviculture capable of being applied to virgin conditions or to all conditions." The lessons taught us by earlier forest history in Europe, the adaptation rather than adoption of European principles to American conditions, and the development of new principles to suit our own special needs are therefore the means by which forestry in the United States will finally solve the silvicultural problems before it at the present day. REGULATION OF YIELD. WORKING PLANS. One fundamental problem has occupied the administration of the national forests ever since their creation, that of working plans as the expression of forest organization leading to sustained yield. Any speculation with regard to the adoption of a system of regula- tion must necessarily refer to the normal stand, whether this is clearly understood and stated or not. Now, there is no such thing as. the 100 per cent normal stand. Consciously or subconsciously the normal stand is taken as the ideal, and from this allowances are made accord- ing to the degree in which the stand deviates from the normal. It is a remarkable fact that even in European forestry no working system has developed of expressing with accuracy the value of allowances^ to be made. This is partly due to the fact that the managed Euro-, pean forests are relatively closer to the normal. Frequent thinnings, and improvement fellings eliminate most of the undesirable indi- i Gaskill, Alfred. Silviculture applied to virgin forest conditions. In Proq, SQQ, Amer. Forest., v, 1, BO, 2, pp. 62-69, 1905, (See p, 67.) FOREST PATHOLOGY IN FOREST REGULATION. 3 viduals from the stand, which is kept as fully stocked as possible. The problem is further simplified by the prevalence of pure stands or of stands composed of two, rarely more, well-matched species. The management of even-aged stands or stands of all ages also permits a relatively close approximation to the normal. All these factors are comparatively rare in our practically virgin for- ests, which are about as far from the normal as possible. As forests they are with few exceptions rather 100 per cent abnormal, and this applies equally well to all unmanaged practically and genuinely virgin forests of the world. The farther the forests are removed from the normal the less can European results from relatively normal stands be applied, and particularly if the abnormality is complicated by the presence of a greater number of commercial species on the same stand, as is so often the case in our forests. It is not to be expected that at the very beginning of its career the Forest Service should have possessed all the facts upon which to base a rational system of sus- tained yield. Intensive work of decades is necessary to secure even the very foundations. It is clear that this lack of fundamental facts must be reflected in any attempt to establish some system of sustained yield and, there- fore, in any policy of regulation of cut. While Kirkland 1 emphat- ically demands a policy of cutting national-forest timber on the Pacific coast on the basis of a sustained annual yield, Greeley,2 on the other hand, points to the difficulties confronting the establishment of a sustained annual yield in the forests of the United States. In his opinion even, " modern conditions governing the distribution and sale of lumber make the sustained yield from the standpoint of a permanent supply for consumers of wood very much of a fiction." We have at the present time no more authoritative statement con- cerning the policy of the administration of the national forests. With regard to the regulation of sustained yield, Chapman 3 arrives at a similar result in discussing the regulation of cut on national forests. Until recently the annual cut permitted upon national forests has been determined by Von Mantel's method, based solely on the present nature of the merchantable stand and a somewhat arbitrary rotation. A few attempts have been made lately to base the cut upon the increment of the forest by use of the Austrian formula. At the same time there has come a general awakening to the fact that our knowledge of the actual increment of virgin forests is conspicuously lacking. Without this knowledge systematic regulation of yield must remain on crude and wholly unsatisfactory founda- tions. The question can not be dodged by quoting the generality that in virgin forests growth equals decay. 1 Kirkland, B. P. The need of a vigorous policy of encouraging cutting on the national forests of the Pacific coast. In Forestry Quart., v. 9, no. 3, pp. 375-390, 1911. 2 Greeley, W. B. National forest sales on the Pacific coast. In Proc. Soc. Amer. Forest., v. 7, no. 1, pp. 42-50, 1912. 3 Chapman, H. H. Coordination of growth studies, reconnaissance and regulation of yield on national forests. In Proc. Soc. Amer. Forest., v. 8, no. 3, pp. 317-326, 1913. 4 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. This "generality," in which almost every word is open to criticism, seems to have become one of the stand-bys of American forestry. 11 finds its chief support in the assumption that our forests to-day, having been untouched by man and exposed to the same factors o\ their surroundings since times immemorial, must represent more 01 less exactly the same character they had 100 or 1,000 years ago. Bui we have practically no genuinely virgin forests; in the great majority of commercial accessible stands — and here we are interested only in these — man has for centuries practiced some kind of primitive for- estry by setting fires. This "Pmte forestry" has changed the aspect of many stands so completely that the term " virgin forests" is fai from being correctly applied. At best, can one speak of scattered virgin stands here and there. Even in the latter the assumption thai the present stand has more or less the same character as 100 to 1,OOC years ago reposes upon another assumption, namely, that here the ecological formation has reached the final stage of development and has come to stay. Of the remaining part of the cited rule of thumt all factors are more or less unknown. Our knowledge of increment is, according to Chapman, "con- spicuously lacking."1 We know just as little about actual extenl and progress of decay in virgin forests, so that the "generality" is reduced to an equation in which all factors are unknown. Besides the term "decay" leaves out all losses from the decrease in numbei of trees steadily going on in the forest, as in every community ol living beings. Prompted, perhaps, by a subconscious realization oJ this fact, the term "decay" in the equation is sometimes supplantec by " deterioration." This makes matters even worse. Deteriora- tion in this connection often means the visible loss irrespective o1 cause. It is primarily a numerical consideration. A number ol trees containing certain amounts of timber annually drop out througt various causes, and this loss is then said to offset the annual incre- ment. Secondarily, it might include loss from decay. In foresl regulation it is not the number of trees and the volume of timber thej produce per acre that count, but the volume of sound, merchantable timber that we can expect to raise; and the only factor in the equa- tion of any value would be, therefore, not decay only and deteriora- tion or numerical loss of individual trees but "total loss." The components of this total-loss factor are known. They include the dropping out of individual trees by death from suppression or "olc age," fire, snowbreak, lightning, windfall, insects, diseases of vita" parts of the tree, and finally loss through decay. What we do nol know are the respective values to substitute for these components in the actual figuring of total loss. 1 More recently Barrington Moore has published a valuable study— Yield in uneven-aged stands— it Proc. Soc. Amer. Forest., v. 9, no. 2, pp. 21&-228, 1914. FOREST PATHOLOGY IN FOREST REGULATION. 5 The same laxity noted in the use of the terms " decay" and " de- terioration" is commonly found in the use of the term "decadence," as applied to a stand or a given species, which is often understood to include individual decadence from old age; that is, arrested or min- imized growth, liability to attack from fungi and insects, and finally decay. The fact that a given species is unusually liable to heart rot does not make it decadent. Many of our most thrifty and aggres- sive species are particularly subject to heart rot. It is also doubtful whether this hypothetical knowledge, if ever attained, of the total rate of total loss in " virgin" forests, as compared with the equally hypothetical rate of increment of the forests as a whole, would help us to any extent. The vastness of our forests in area creates a tendency either to think in broadest terms and to overlook the fact that a forest is an artificial unit made up of natural units, the stands with all their immense variety of character, or, on the other side, to take a familiar unit and to transfer its characteristics to the whole. The latter mistake is more easily remedied than the first. As a science, forestry must be founded upon inductive methods. Inten- sive study of detail alone can form a solid basis for the formulation of principles. What is needed is exact studies of all components of the total-loss factor per species before we attempt to fix the total-loss factor for the stand. Such detailed studies will be easiest in all-aged pure stands of a thrifty species little liable to decay. Unfortunately the vast majority of stands on national forests in the West are composed of two to five or more species of very different characters. It may be that the total annual loss equals the annual increment in some of the medium long-lived species of the pine group least liable to decay. It can not be true for the extraordinarily long-lived redwood and big tree, with their unusual resistance to decay, insects, and storms. It is equally untrue for all shorter lived species much exposed to decay and other influences that make for loss. Lilocedrus decurrens, for example, although most aggressive and thrifty, is from an early age on liable in an uncommon degree to the attacks of Polyporus amarus, which renders as much as 70 or 80 per cent and even higher per- centages of the stand completely unmerchantable. Merchantable incense cedar is of high value; so much the greater, then, is the total-loss factor The same is, mutatis mutandis, true for white fir and a number of other species. For all these the increment is not only offset but far exceeded by the decay of the valuable heartwood; the total annual loss is far greater than the annual increment, although numerically the loss may not be apparent. The gain through increment, we must remember, consists of sap- wood of little value; the loss by decay, on the other side, affects the 6 BULLETIN 275, C. S. DEPARTMENT OF AGRICULTURE. valuable heartwood. Neither is there any constant accumulation of gain; after some years the sapwood is turned into heartwood and as such becomes liable to decay. In other words, in trees of this group infected with heartwood-destroying fungi, the value of newly formed wood is small; when it becomes valuable by transformation into heartwood it becomes subject to decay — that is, loss. This loss from decay is by its very nature as a heart rot confined to those individ- uals in which heart-rot formation has taken place. All trees below the age of heartwood formation do not enter into consideration. In speaking of a given stand the representation by ages must be oi prime importance. In all considerations of regulation it is neces- sary, therefore, to make a clear distinction between forests and stands, between many-aged and even-aged stands, between mixed and pure stands, with particular emphasis on the composition of th€ stand as to species. All generalization is not only useless but mis- leading. But in full realization of the almost complete lack of fundamental knowledge, American forestry is confronted with the urgent neces- sity of adopting, even temporarily, some kind of a system of regula- tion of yield. Whatever this system may be, its tentative, tempo- rary, and local character can not be overemphasized. Various attempts at adopting local temporary systems have found an expression in the shape of working plans. Inseparable from the problem of working plans is the choice of a rational rotation and cutting cycle. ROTATION. The gleanings in American literature treating on the choice of rotation from a general point of view are rather meager, outside of a few well-known handbooks, such as those by Recknagel,1 by Fernow/ and by Roth,3 particularly in so far as the practical application tc our virgin forests is concerned. Recknagel 4 excludes financial rota- tion from North American forests with the following words : Since this method of calculating the rotation [financial rotation or that of highesl soil rent] is suitable only to very intensive conditions, it would serve no useful pur pose to elaborate it at this point. On the other hand, the strong influence of European forestry is clearly felt in the ever-recurring advice to adopt some kind of a financial rotation in the national forests of the United States. Kirk- land 5 is of the opinion that — 1 Recknagel, A. B. The Theory and Practice of Working Plans (Forest Organization), 235 pp. New York, 1913. 2 Fernow, B. E. Economics of Forestry, 520 pp. New York, 1902. 3 Roth, Filibert. Forest Regulation, or the Preparation and Development of Forest Working Plans 218 pp., illus. (maps). Ann Arbor, Mich., 1914. (His Michigan Manual of Forestry, v. 1.) < Recknagel, A. B. Op. cit., p. 39. sKirkland, B. P. Working plans for national forests of the Pacific Northwest. In Proc. Soc. Amer. Forest., v. 6, no. 1, pp. 16-37, 1911. (See p. 21.) FOREST PATHOLOGY IN FOREST REGULATION. 7 A rotation based on the financial rotation, possibly modified somewhat towards the rotation of the highest income, is no less adapted to Government forestry than to pri- vate forestry. Greenamyre J advocates a financial rotation in the composite type of the Apache National Forest, the " rotation of greatest volume pro- duction being out of question." In his specific recommendations for western yellow pine, Douglas fir, and blue spruce, however, rota- tion of greatest volume plays a far greater role than financial rota- tion. Such important factors in financial rotation as soil capital, quality increment, and rent are neglected or only hinted at. Value increment and depreciation enter into his calculations in a general way only, evidently from a lack of exact figures. Barrington Moore2 expresses himself strongly against the adoption of a financial rotation. It would be out of place in this paper to enter into a discussion of the possibility at the present time of fixing a rotation of greatest income or a financial rotation more deeply than to point to the immense difficulties encountered as soon as we try to substitute actual values for the factors entering into their computation derived from experience in our own country. We lack at the present time the very fundamentals on which to base the determination of highest forest rent or highest soil rent. The Forest Service has, in full realization of the uncertainty of almost all factors which would or should enter into a financial rota- tion formula, adopted, for the present at least, a tentative silvicul- tural rotation of maximum-volume production. The factors entering into the determination of silvicultural rotation or of greatest volume being more easily accessible, it is quite natural that American forestry should show a tendency toward its applica- tion, as shown in a number of published and unpublished working plans. Attempts at fixing some kind of a rotation age are found in several publications. Woolsey 3 tentatively proposes a rotation of 200 years for yellow pine without giving a basis for the choice of any particular system of rotation. Barrington Moore4 says that on the Plumas National Forest "the rotation should theoretically be that of maximum- volume produc- tion. The use of a financial rotation by the Government, in a region 1 Greenamyre, H. H. The composite type on the Apache National Forest. U. S. Dept. Agr., Forest Serv. Bui. 125, 32 pp., 4 figs., 1913. (See p. 30.) 2 Moore, Barrington. The essentials in working plans for national forests. In Proc. Soc. Amer. Forest., v. 6, no. 2, pp. 117-128, 1911. (See p. 126.) sWoolsey, T. S. Western yellow pine in Arizona and New Mexico. U. S. Dept. Agr., Forest Serv. Bui. 101, 64 pp., 11 figs., 4 pis., 1911. (See p. 51.) * Moore, Barrington. Chapman's method of studying yield, p. 93, 1913. To accompany forest plan, Plumas National Forest, district 5. Appendix (continued), Silviculture. (Unpublished. Furnished by courtesy of the U. S. Forest Service.) 8 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. capable of producing large saw timber, can not be justified. * * * It would probably be better to fix the rotation at the period during which the rate of volume production is greatest or shortly after it, provided this is long enough to give the most valuable product." Hunger * comes somewhat closer to a consideration of the financial factors for a rotation of Douglas fir in pure even-aged stands in the Pacific Northwest. From the quotations given, one fact stands out clearly : We are still groping more or less in the dark where choice of rotation is con- cerned, and we are even lacking the fundamentals upon which to base the principles to govern us in making a proper choice. It also appears that in many cases the term " actual felling age" should be substituted for rotation. Rotation in itself signifies return or succes- sion in a series. Fernow 2 has warned, as early as 1905, against mix- ing up i ' actual felling age, the time when a stand is actually cut or to be cut, and normal felling age (rotation), the time when in a scheme of continued management it is proposed to have it cut again and again — a mere standard time. Few stands are cut in the age of the rotation determined for the forest as a whole." Where a " rotation" of yellow pine, for instance, of 200 years is advocated, it is evident that this can not be meant to constitute the fixed period at which yellow pine should be cut again and again in the future. It is really the actual felling age, the time when a given stand of yellow pine is actually to be cut in the future, not a succession of 200-year periods. The rotation itself will be much shorter, as European experience has shown us. Moreover, it is more than doubtful whether our successors in 200 to 400 years will pay much attention to the rules we may try to lay down for so remote a future. CUTTING CYCLE. The impossibility of predicting with even a modest degree of proba- bility what will happen in the future and of anticipating changes in conditions of an economic nature is responsible for the vagueness with which the question of fixing definite cutting cycles is treated. Tenta- tively, cutting cycles of about 50 years have repeatedly been advo- cated for uneven-aged stands (mixed and pure) under the selection method, as a policy to be followed on virgin national forests. If present economic conditions should prevail in the next 50 years — that is, if the demand for timber should continue to fall far short of the actual annual increment — it would hardly pay a lumbering concern of the future to extend its operations to cut-over areas before 50 to 60 years had elapsed. Even then it seems doubtful whether the * Hunger, T.T. The growth and management of Douglas fir in the Pacific northwest. U.S.Dept.Agr., Forest Serv. Circ. 175, 27 pp., 4 figs., 1911. 2Fernow, B. E. Forest terminology. In Forestry Quart., v. 3, no. 3, pp. 255-268, 1905. (See p. 264.) FOREST PATHOLOGY IN FOREST REGULATION. 9 amount of timber contained in the few overholders left as seed trees and in individuals at or just below the diameter limit established in a first cutting would prove attractive to purchasers of the future, pro- vided always no change in the lumber market should take place. The diameter limit now fixed on many national forests may be said to be about 12 inches, varying somewhat with the species and local conditions. Few trees below this diameter will reach such dimen- sions in 50 years as to form a merchantable stand, judged by our standards of to-day. If it is unwise blindly to take over principles and policies developed and more or less accepted in countries with old-established and far- advanced forestry and apply them to the first stages in the organiza- tion of our virgin forests, the study of the history of the forestry movement and development in other countries can not but be of the greatest practical value. We are justified also in assuming that the history of forestry will repeat itself and that forestry in all countries with large virgin or practically virgin forests in touch with the gen- eral market will run through the same phases of development as it did during the last centuries in central Europe, but at a very much faster pace, owing to the enormously enhanced facilities of transpor- tation and marketing and the rapidly increasing demand for timber. If this be true, a cutting cycle of about 50 years may prove too long. To judge from the development of timber values in Europe, our once cut-over stands should prove attractive in a shorter period. In determining the duration of cutting cycles, it is reasoned that the accessible virgin timber in the national forests should be cut once before operations return to the first areas logged over. How much time this first culling may consume we have no means of telling. It should be remembered, however, that the system naturally present- ing itself is that of selection cutting, and although there is a decided tendency toward heavier marking approaching clean cutting, this latter should be taken cum grano salis. Actually, the reproduction left includes all individuals up to and sometimes beyond 12 inches diameter breast high; that is, trees that have reached a considerable age and that in 50 years will have grown to what would be classed in European forestry as veterans. CUMULATIVE RISE. In fixing long-term cutting cycles, a most important point has not been sufficiently emphasized, namely, the " cumulative risk" from fire, windfall, frost, and so-called deterioration to which a given stand is exposed during so long a period. The longer the cycle the greater the ratio of risk. The unparalleled development of fire protection in the national forests of the United States, it is true, promises fairly to exclude actual destruction from fire on any large scale; but, as long as 10 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. there will be fires from unpre veritable sources (lightning) , the risk in extended cutting cycles increases from year to year with the growth in value of the stand. The shorter the period in which a merchant- able stand can be produced and turned into cash the smaller will be the risk of loss. Loss from windfall is inevitable in many localities as a direct con- sequence of selection cutting. It is clear that the cumulative risk of a longer cycle is far in excess of a shorter one. Evidently, devas- tating windstorms are more likely to occur during a period of 50 years than during a shorter one. Moreover, the loss in cash value, even in single trees, from windfall is bound to be heavier in the older stands. The larger, bulkier, and therefore the more valuable the tree, if sound, the more it is exposed to windfall. Falling trees in brushing against their standing neighbors not infrequently cause more or less serious wounds by bruising or tearing off the bark. The greatest risk, however, involved in the long cutting period is from " deterioration," so called. In nature a steady process of elimination goes on. Of thousands of seedlings springing up together in dense growths, comparatively few reach sapling size, very few grow into poles, and fewer, even, to standards. This natural thinning through competition in the fight for soil, food, and light is furthered by various dangers to which the young plants are exposed, such as from certain insects, foliage and twig diseases, injury from mammals, snowbreak, frost, and drought. Later, the surviving members of the stand are confronted with dangers from the same and other sources, such as suppression, lightning, in- sects, frost, and decay. The elimination of the weaker members effects a selection of older, well-established individuals, some of which may still suffer from the competition of their thriftier neighbors, but are not forced out of the community, or, to use Fernow's 1 well- chosen terminology, trees which are "oppressed," not suppressed. As long as improvement cutting on a larger scale on the national forests is impossible, the percentage of oppressed trees will depend upon the length of the cutting cycle. Both these oppressed trees and their more favored companions are exposed to dangers from which their earlier life was free. Frost does a good deal of damage; here we are less interested in the damage done to the foliage or to the bark than in those more or less long cracks in the wood which are caused by very low tempera- tures. In cold weather the wood cylinder shrinks more in a tan- gential than in a radial direction. Particularly at sudden low temperatures, when the volume of the outer layers decreases rather suddenly while the inner layers are still free from frost and have i Fernow, B. E. Forest terminology. In Forestry Quart., v. 3, no. 3, pp. 255-268, 1905. (See p. 266.) FOREST PATHOLOGY IN FOREST REGULATION. 11 shrunk but little, differences in internal tension will cause the outer layers to split vertically. With rising temperature the frost crack closes. Not always is the bark able to stretch sufficiently over a frost crack. Often the bark tears open, and if low temperature occurs again and again, the cracks will not be able to heal over and will remain open for many years, giving the air access to the heartwood and incidentally allowing spores of wood-destroying fungi to ger- minate and infect it. Even if no infection takes place, these frost cracks very seriously impair the value of the timber. The older and bulkier the tree the greater is the danger of frost-crack formation. The risk naturally increases with the length of the cutting cycle. Infection, of course, can take place only through open frost cracks; internal frost cracks, besides impairing the value of the timber, can not be without influence on the chemistry and physics of the wood. Although lightning occasionally strikes the smaller trees, even poles and saplings, it is to be expected in the nature of things that taller trees will be more exposed to injury from this cause. Very little is known, so far, as to the actual damage done by lightning in our forests. Destruction of individual trees has been frequently reported, and Plunimer 1 gives a series of illustrations of injury to forest trees from lightning. He treats, however, only of those very gross cases in which even the least educated eye will recognize the cause of the injury. We know through Robert Hartig's2 classical investigations, which were continued by Von Tubeuf, that destructive lightning is rare in comparison to the overwhelmingly greater number of cases of lighter injury from lightning, varying from more or less large wounds visible on the outside of the tree to the small and insignificant local killing of parts of the cambium and of the living bark which can only be detected by careful dissecting. The symptoms of lightning injury in our forest trees are easily .recognized from Hartig's excellent descriptions. They are particu- larly common and conspicuous in white fir. For practical purposes, we have to consider here only those forms of lightning injury which in some way endanger the life, the health, or the commercial value of the tree; this will include not only actually destructive cases, but also very large numbers of lesser injuries. The accumulation of risk during a long-time cutting cycle becomes self-evident, particularly in view of the fact that the danger from lightning increases quite out of proportion to the increase in height of the tree and the development of the root system. i Plummer, F. G. Lightning in relation to forest fires. U. S. Dept. Agr., Forest Serv. Bui. Ill, 39 pp., 16 figs., 1912. 2Hartig, Robert. Untersuchungen uber Blitzschlage in Waldbaumen. In Forstl. Naturw. Ztschr., Jahrg. 6, 1897, Heft 3, pp. 97-120; Heft 4, pp. 145-165; Heft 5, pp. 193-206. 83 figs. Hartig, Robert. Neue Beobachlungen uber Blitzbeschadigung der Baume. In Centrbl. Gesam. Forstw., Jahrg: 25, 1899, Heft 8-9, pp. 360-3S1, figs. 47-71; Heft 12, pp. 523-544, figs. 81-110. 12 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. Although young trees are also exposed to the attack of insects, it is clear that a colony of bark beetles will prove far more injurious in killing a merchantable tree than in killing a small pole. Moreover, certain insects seem to have a predilection for larger sizes. The probabilities of attack increase with the length of the cutting cycle. Besides, the older the tree and the more it has been exposed to wounding the more liable does it become to attack by wood-boring insects which materially reduce the value of the timber. The timber contained in trees killed by lightning, as long as they are not destroyed, and in those killed by bark beetles may be utilized, and, with increasing timber values, will be utilized before they deteriorate. The few veterans which have withstood the many dangers of earlier life do not go on living forever; they finally succumb like the rest. It is still an open question whether forest trees are theoretically im- mortal and die only through the devastating influence of severe storms, lightning, insects, certain diseases caused by fungi, such as Armillaria mellea and Fomes annosus, or because the root system of the veteran finally has exhausted all available resources of the soil within its reach. As we are interested here only in the future of cut- over areas in relation to the length of the cutting cycle, it is unneces- sary to enter into a discussion of this question. The cutting cycle for any one species will in all probability never be long enough to raise individual decadence from old age to the rank of an influencing factor. We should bear in mind, however, that individual decadence is not in itself deterioration unless decay sets in. The importance of the reduction in the timber value of the tree through the agency of fungi, on the other side, can not be overempha- sized. This reduction in timber affects either the prospective timber values — that is, the increment — or the present stock, or both. In the first case, the fungi in question (mostly Pyrenomycetes and rust fungi) inhabit living tissues of the foliage or of the young bark. The con- tinuous drain on the assimilates of the foliage either in the leaves proper or on their way down through the bark is evidenced by a decrease in increment of the tree, which in long cutting cycles will represent a very considerable loss in timber values. In other words, trees affected with foliage or bark diseases will be far from yielding the timber we might expect from sound trees. It must be mentioned that losses in prospective values are not alone due to fungi; mistle- toes and leaf-inhabiting insects are responsible for enormous deficits in yield. The economic role of the fungi, mistletoes, and leaf-inhab- iting insects in our virgin forests is highly important and will remain so for a long time, on account of the difficulties connected with their control and even more on account of our very limited knowledge con- cerning their life histories and specific action. More intensive studies FOREST PATHOLOGY. IN FOREST REGULATION. 13 on the members of this group must be left to the future. At the present time we are more interested in the preservation of our actual timber, including such values as will be formed in the near future. Actual timber values are seriously endangered by wood-destroying fungi, all of which belong to the Hymenomycetes. With the exception of a very few (Armillaria mellea, Fomes annosus), which in attacking living roots first cut down the increment of their host and then invade the wood of the bole, they all inhabit the heartwood and generally leave the sapwood intact. As the principal timber values are stored in the heartwood, the enormous damage they are able to cause is all the more in evidence. All of these fungi are adapted to given hosts or groups of hosts; these groups are seldom very large. Polyporus amarus, for example, the cause of the extremely destructive heart rot of Libocedrus decurrens, can not grow, as far as is known, in any other host species. Trametes pini, on the other hand, attacks a number of pines, Douglas fir, and other conifers. The composition of the stand, as well as the representation of species, is therefore an im- portant factor in the ecology of these fungi. Only those fungous spores which land on trees of the species to which they are adapted have a chance after germination to enter into the tree. Being strictly heartwood inhabiting, these fungi, with the excep- tions mentioned above, can, of course, only attack trees which already have formed heartwood. But as they are unable to penetrate the bark, they are harmless unless their spores are carried on to some wound or opening (branch stubs) in the protective skin represented by the bark. The longer the host is exposed to wounding, the greater will be the chances for infection. As might be expected, therefore, the losses from decay in standing living trees are enormous in virgin forests. Even in the best managed forests of Germany losses from decay are heavy. Moller,1 in figuring the damage done by Trametes pini in the pine forests of the Prussian Government, arrives at the astounding figure of more than 1 million marks (about $250,000) annual loss from this source alone. In the period from 1905 to 1908 the Prussian Government spent $87,480 in the control of Trametes pini in its pine forests.2 In 1914 this sum had increased to about $120,000.3 In American literature no reliable figures are available relating to the annual loss from decay in standing timber in virgin forests. Such figures can be obtained only by exact studies on representative areas, the methods of which the writer has been trying to work out 1 Moller, A. Uber die Notwendigkeit und Moglichkeit wirksaruer Bekampfung des Kiefernbaum- schwammes Trametes pini (Thore) Fries. In Ztschr. Forst- u. Jagdw., Jahrg. 36, 1904, Heft 11, pp. 677- 715, pis. 4-5. 2 Moller, A. Der Kampf gegen den Kiefernbaumschwamm. In Ztschr. Forst- u. Jagdw., Jahrg. 42, 1910, Heft 3, p. 133. 3 Moller, A. Der Kampf gegen den Kiefera- und Fichtenbaumschwamm. In Ztschr. Forst- u. Jagdw., Jahrg. 46, 1914, Heft 4, pp. 193-208. 14 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. during the last few years. In reason, all figures relating to loss in timber from decay, insects, lightning, etc., should apply only to such forested areas as are accessible at present or which will be in all probability accessible in the not too remote future. Inaccessible stands, whatever their protective value, do not represent timber values, and it is obviously wrong to include them in any estimate of the damage done to our timber stock on hand. The rate of progress of decay in the individual tree is altogether unknown beyond vague guesses. Hartig 1 has tried to figure the^-ate of growth of the mycelium, for instance, of Pomes igniarius. Moller 2 has made an attempt to figure the rate of growth of Trametes pini and resulting decay in Pinus silvestris from actual measurements in artificially infected trees. It is clear that unless such experiments are carried over a great many years, only the rate of growth of juvenile fungus plants starting from the infection can be measured, which can not be taken directly as a guide for figuring the growth of the older or mature fungus plants. Besides, the experiment is based upon the assumption that the fungus, after once having gained access to the interior of the tree, is independent of possible individual differences of its substratum, or, in other words, that the rate of growth is a fixed factor, irrespective of individual properties of the heartwood. This assumption has no solid basis. The rate of growth of the fungus plant, and therewith of decay, is undoubtedly one of the most inaccessible chapters of forest pathology, on account of the difficulty in finding a stable point of issue. There is at present no reliable method known of deter- mining the actual extent of decay in the standing living tree. In- direct methods are the only means presenting themselves to-day; they leave much to be desired with regard to accuracy and can not be expected to yield results unless carried on over a long period. What we do know is that decay in standing living timber from heartwood-destroying fungi causes very heavy losses and that decay is progressive. Sporophores develop on decaying trees, and the dis- ease spreads through spores from one tree to other individuals of the same and sometimes of other species. Moreover, the decay starting from an incipient infection progresses in the heartwood of the in- dividual tree until its most valuable lumber is destroyed. Decay being progressive, the cumulative risk from this source in long cutting cycles is therefore far greater than in the case of lightning or other injurious agents. Unlike insects, heartwood-destroying fungi have few or no natural enemies; there is no such thing as "biological control" of decay. , 1 Hartig, Robert. DieZersetzungserscheinungendesHolzesderNadelholzbaumeandder Eiche ... p. 116. Berlin, 1878. 2 Moller, A. Der Kampf gegen den Kiefernbaumsctiwamm. In Ztschr. Forst- u. Jagdw., Jahrg. 42, 1910, Heft 3, pp. 129-146. (See p. 145.) FOREST PATHOLOGY IN FOREST REGULATION. 15 PERIOD OF TRANSITION. American forestry stands now at the very beginning of a period of transition from the handling of virgin forests to actual forest regula- tion. The most urgent problem, therefore, consists in how to take care of our forests as we have them, with all their defects, with in- dividual decadence and decay, and to leave them to future genera- tions in as favorable a state as possible, judged by our very limited insight of to-day. At the present time the only means at the disposal of the Government to carry out any plans in forest regulation based upon what appears to us as sound silviculture is through timber sales. The Government does not and can not cut its own timber. It is therefore entirely dependent upon a highly variable outside factor with regard to the most important part of its silvicultural work, a factor over which it has but little control. All attempts at the regu- lation of yield must then be concentrated on timber-sales areas. A comparison between the area actually cut over annually and the total national-forest area that may eventually become accessible to logging operations will show the severe hardship under which the Government is forced to work. Moreover, timber sales do not always occur where they are most needed from a silvicultural point of view, nor do they always cover the entire natural units upon which it is desirable to prepare for a system of regulation. A com- prehensive system of regulation on a larger scale following natural units is out of the question as long as the Government is not in a position to do silvicultural work on its own land where it is most needed. The aim of the Forest Service at the present time consists less in how to do the greatest amount of good to future generations than in how to do the least harm and at the same time to do justice to our present-day conditions. Instead of exhausting our energies in sterile speculation of what might happen in 100 to 200 years from now, there is a -strong tendency toward applying them first to the analysis of the most urgent needs of to-day and then to the exact and painstaking study of all the innumerable factors which enter into a comprehensive plan for the future structure of American forestry. It is well to remember that so far, not even the methods leading to the majority of such studies are worked out. The necessity of taking care of our present-day timber supply and of providing for the future in an exten- sive rather than intensive way has found strong expression in Chap- man's 1 " American Method," where regulation is based not only on present volume and annual growth, but also on the " actual condition and amount of timber in the different age classes, with approximate knowledge of the behavior and condition of the age classes for an 1 Chapman, H. H. Coordination of growth studies, reconnaissance and regulation of yield on national forests. In Proc, Soc. Amer, Forest., v, 8, no. 3, 1913. pp, 317-326. (See p. 323.) 16 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. extensive future period." If " condition ' ' is defined as state of health, not only as far as thrift iness of growth is concerned, but also with special regard to degree of merchantability as influenced by decay, the condition factor becomes a subject of pathological study. Condition of the timber we hope to raise for the future, in the definition as given above, has a strong bearing on the possible regulation of yield. There can be no sense in figuring cutting cycles or rotation for future generations to follow unless we assume X that our successors will find the area we have cut over covered with a stand not only apparently but really merchantable; in other words, with timber that is not rendered valueless by decay. The most ingenious speculation as to future yield is without any value whatever unless we have some way of figuring how long the steadily increasing but admittedly perishable timber stock can be left in the forest before it is liable to destruction by fungi. The most important problem before us, therefore, is the determi- nation in definite values of the condition of timber stock, present and future. CONDITION OF TIMBER STOCK. The condition of the timber as a factor in regulation may be expressed as the relation of the volume of timber destroyed or rendered unmerchantable by injurious agencies to the ideal volume of merchant- able timber; or, in so far as forest regulation is interested not merely in the present but in the future, as the relation of the mean annual total loss to the mean annual increment. It has already been pointed out that the concept of the relation of the mean annual total loss to the mean annual increment is without any value whatsoever as long as both factors are unknown. We are beginning to know in a small way something about the mean annual increment of certain species in certain types of some of the national forests. We are still completely ignorant as to the influence that the only silvicultural act of any importance open to the Forest Service, that is, cutting on timber-sales areas, will have on the increment of the remaining trees. This knowledge will come in due time. The value of the total-loss factor is altogether unknown. In order to attack this problem it is necessary to analyze it, to reduce it to its several components, and to study each in its turn. By synthesis the total loss can then be computed and the true relation to increment determined. TOTAL LOSS. The analysis of total loss already given shows that its components are known, but not their values. Of all these components the most important, the one that has the strongest bearing on the value of the stock of timber at hand, is loss from decay or heart rot caused by a group of heartwood-destroying fungi. Very young trees are not FOREST PATHOLOGY IN FOREST REGULATION. 17 susceptible to heart rot. No heart rot is possible before heartwood is formed. Unfortunately, we do not know anything about the formation of heartwood in our American species with relation to the age of the tree. The younger trees, while at present immune, will, in growing up and after formation of heartwood, become just as subject to heart rot as are their older companions. It is, then, of prime importance to know at what age living trees of a given species become particularly liable to attack from the one or more heart wood-destroy- ing fungi that use their heartwood as a source of food. It is, further, of the utmost importance to know whether there are any conditions in the tree or outside of it that exert an influence over the develop- ment of the fungi once they have gained access to the heartwood of a tree to which they are adapted. Beyond general statements to the effect that overmature trees do deteriorate from heart rots, very little information is to be gathered from American literature concerning the average age at which certain tree species become liable to attack from heartwood-destroying fungi. Greenamyre 1 mentions that in the Apache National Forest the decay in Douglas fir " no doubt largely offsets the growth'' after the age of 210 years is reached. Hunger 2 gives a little more specific information: The amount of decay found in living Douglas firs up to the time they are 150 years old or so is very small, but in mature and overripe timber there is a great deal of defect due to decay. . . . Douglas fir trees resist infection from fungi well until they become mature, when, because of the opening up of a stand, breakage, and scars due to the action of the elements and of fire and insects, and also because with advanc- ing age their resistant power becomes less, they offer entrance to fungi. It is not clear from the context whether Hunger's figures are an estimate or are based on actual methodic investigation and measure- ments. Findley Burns,3 in speaking of conditions on the Crater National Forest, gives the following information : Many of the older Douglas firs are affected by a dry rot. . . . White fir is especially susceptible to decay, and many trees above 40 inches in diameter on the forest are so rotten as to be valueless, even for cordwood. In the latter case, age is supplanted by diameter, which answers perfectly well if diameter invariably corresponds to age. Barrington Hoore and R. L. Rogers4 incidentally give some interesting notes on the age of infection of balsam fir, which on the 1 Greenamyre, H. H. The composite type on the Apache National Forest. U. S. Dept. Agr., Forest Serv. Bui. 125, 32 pp., 4 figs., 1913. (See p. 31.) 2 Hunger, T. T. The growth and management of Douglas fir in the Pacific Northwest. U. S. Dept. Agr., Forest Serv. Circ. 175, 27 pp., 4 figs., 1911. (See p. 10.) s Burns, Findley. The Crater National Forest. U. S. Dept. Agr., Forest Serv. Bui. 100, 20 pp., 4 pis., 1911. (Seep. 12.) 4 Moore, Barrington, and Rogers, R. L. Notes on balsam fir. In Forestry Quart., v. 5, no. I, pp. 41-50, 1907. 98035°— Bull. 275—16 2 18 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. area investigated was 50 years in pure stands and 85 years when mixed with hardwoods. They speak of butt-rot only, without specifying the cause; unfortunately, the numerical basis from which their figures are derived and their methods are not given. The bearing on management of the age at which decay becomes a seriously damaging factor is very rarely realized. Clapp,1 in speaking of- incense cedar and white fir, clearly recognizes that where these "inferior" species are also defective, "an attempt should be made, at least in selection stands, to reduce their rotation to one which will produce sound timber." In a recent article, D. T. Mason 2 advocates a rotation of 100 years for western white pine, on the ground that this species on the average gives a maximum yield at this age and that from about the same age fungi, and particularly insects, generally succeed in doing a large amount of damage. It would serve no purpose to continue quoting the few and scat- tered notes on the relation of age to decay, of a similar indefinite nature found in American literature. By way of consolation, it may be said that foreign literature does not abound very much more than our own in definite information regarding this point. Although the importance of the age at which forest trees are most liable to attack from heartwood-destroying fungi is frequently hinted at in German literature, Martin 3 is the only German forester who, to the knowledge of the writer, has given more than a cursory discussion of the relation of this age to rotation. In speaking of the immense damage done in Prussian pine forests by Trametes pini, he attempts to show from somewhat meager material how the increase in loss from this cause should lower the rotation. All computations of the amount of decay in German forests must necessarily be incomplete, since from an early age all undesirable individuals, including, as a matter of course, all trees with visible signs of decay, are eliminated in improvement cuttings. The result is a stand of a comparatively high degree of soundness. Even in such stands Martin finds (p. 688) that in a given district the per- centage of decay in wood good for fuel only in the 100-year class was 11, in the 120-year class 22, in the 130-year class 31, in the 140-year class 37, and in the 160-year class 42. He points out that in unsound stands the felling age must be lowered in order to secure the maximum income. Martin 4 again discussed similar ideas in 1910. 1 Clapp, E. H. Silvicultural systems for western yellow pine. In Proc. Soc. Amer. Forest., v. 7, no. 2, pp. 168-176, 1912. (See p. 175.) 2 Mason, D. T. Management of western white pine. In Proc. Soc. Amer. Forest., v. 9, no. 1, pp. 59-68, 1914. 3 Martin. Der Einfluss des Baumschwammes auf die Umtriebszeit der Kiefer. (Kritische Vergleichung der wichtigsten forsttechnischen und forstpolitischen Massnahmen deutscher und ausserdeutscher Forst- verwaltungen.) In Ztschr. Forst- u. Jagdw., Jahrg. 35, 1903, Heft. 11, pp. 685-690. * Martin. Die Umtriebszeit der Kiefer in den Staatsforsten von Preussen, Bayern, Elsass-Lothringenj Hessen und Anhalt. In Forstw. Centrbl., Jahrg. 54, 1910, Heft 7, pp. 363-387. FOREST PATHOLOGY IN FOREST REGULATION. 19 Holier1 touches upon the same point in a general way, without trying to give the problem a more solid basis by exact material. The following sentence is worth quoting : Whilst the mean annual increment of the stand is slowly decreasing, the mean annual increment of decay is steadily on the increase. Here is the clue to the proper silvicultural valuation of cutting cycles or rotation on a pathological basis. The time at which a tree or a stand is to be cut may range from a comparatively low age to the age of maximum production of lumber, according to the special needs the forester has in view; but the upper limit of this range should not lie beyond the period at which the gain from increment is offset by loss from decay, irrespective of the ideal amount of timber a sound tree or stand might produce under favorable conditions. Not to cut a tree or a stand in which increment is offset or exceeded by loss from decay, where cutting is possible, constitutes an unsilvi- cultural act. Oilman 2 informs us that silver fir in the Black Forest, Baden, Germany, "is unable to stand a long rotation, for after 100 years the per cent of rotten timber increases greatly." Here, ,the influence of loss from decay on rotation is clearly shown; but it is to be noted that the loss factor is derived in a purely empirical way and is not based on exact studies. Hemmann 3 has published some interesting and exact studies on the damage done by Trametes pini in Scotch pine in a small area under regular management; that is, where the disease was partly eliminated by improvement cuttings. All this somewhat scanty European material, valuable though it undoubtedly is for transatlantic forestry, is of very little help to us. What holds good for the managed forest raised in a century of careful nursing can not serve for more than a clue in genuinely or practically virgin forests, whether they be located in the United States, in Canada, in Chile, in India, or in Siberia. Again we are confronted with the necessity of working out our own problems in our national forests. INFERIOR SPECIES. Most of the timbered parts of the national forests, especially in the West, are practically virgin, seriously injured by fire, composed of even-aged or many-aged stands, and generally of more than one species, which are more or less exposed to heart rot caused by one or more specific fungi. 1 Holler, A. Uber die Notwendigkeit und Moglichkeit wirksamer Bekampfung des Kiefernbaum- schwammes Trametes pini (Thore) Fries. In Ztschr. Forst- u. Jagdw., Jahrg. 36, 1904, pp. 677-715. (See p. 712.) 2 Oilman, E. C. V. Forest types of Baden. In Forestry Quart., v. 10, no. 3, pp. 440-457, 1912. (See p. 452.) 3 Hemmann. Uber den Schaden des Kiefernbaumschwammes. tn Allg. Forst- u. Jagdztg., Jahrg. 81, pp. 336-341, 1905. 20 BULLETIN 275,, U. S. DEPARTMENT OF AGRICULTURE. A systematic study of the relative position occupied by the heart- rot factor in the economy of the forest presupposes a knowledge of the morphology and biology of the specific fungi attacking the species of which the forest is made up. Morphologically, most fungi of economic importance are well known; biologically, there is much left to be learned. The susceptibility of each host species to specific attack, the age at which a given species becomes liable to attack by the fungi adapted to live on it, the age at which a given species is liable to suffer appreciable loss from this source, the relation of accessory factors in the tree and outside T)f it to fungus growth, the relative loss caused by each fungus in its specific host — all these are funda- mental problems which must be solved for every important fungus on every commercial species of our forest trees. So far, no definite and clear, comprehensive answer can be given to any one of these questions. In determining upon a suitable starting point in the overwhelm- ingly large amount of work before us, the question is that of deciding where such work is most needed at the present time. Leaving out of consideration such species as bigtree (Sequoia gigantea), which is never cut in national forests, and redwood (Sequoia sempervirens) , which is hardly represented in national forests, the commercial timber of the national forests in the western part of the United States is composed of coniferous trees, such as pine, larch, spruce, fir, Douglas fir, hemlock, incense cedar, and western white cedar. They constitute the goods the Government has to offer for sale. Of these the pines cause least trouble. Pine lumber is eagerly sought and pays good prices; moreover, the loss from decay is com- paratively small. In Government timber sales there is never any difficulty about pine timber; the more the Government has to sell on a given tract the better. Not so with the so-called "inferior species." The term " inferior or undesirable species," as it is generally applied, is originally not a technical one. It is meant to designate those more or less heavily represented commercial species which suffer from a distinct prejudice on the part of the purchaser. If we could grow sound incense cedar, for instance, there would be a ready market and a good price for every foot, board measure, of it that the Government could offer on timber sales. Distinction should be made between species which actually yield technically poor lumber, even if sound, and species, on the other hand, which when clear and sound yield valuable material, but which are in general underrated by the pur- chasing public on account of the extraordinary prevalence of decay. An example of the first class is eastern hemlock. An example of the second class is incense cedar, which, although of excellent quality when sound, suffers from a very bad reputation among lumbermen, FOREST PATHOLOGY IN FOREST REGULATION. 21 because it is so very commonly rendered useless by dry-rot or pin- rot. The numerically and economically most important species of the accessible merchantable national forests in southern Oregon and California are sugar pine, Jeffrey and yellow pine, Douglas fir, white fir, and incense cedar. To these may be added, for certain localities, lodgepole pine, red and Shasta firs, western larch, Sitka spruce, western hemlock, and western red cedar. Of the six main species, all three pines command good prices. They are comparatively free from heart rot. White fir and incense cedar are in general so badly defective that, as Clapp1 states, they are " under present conditions almost a drug on the market." Douglas fir stands in a class by itself. The value of its timber is well known; in fact, it competes with pine timber as far as quality for many purposes is concerned. On the other hand, Douglas fir is in a far higher degree susceptible to the attacks of several heartwood-destroying fungi, and, although it is not classed among the inferior species, the very prevalence of decay makes it less desirable than the pines, from a silvicultural point'of view. Incense cedar and white fir are frankly classed as inferior. Whether this view is correct or not, we must reckon with it as a powerful factor of influence in all timber sates where these species occur. They are the lower grade by-products of the factory, the production of which can not be stopped; it goes on hi spite of what we may wish or what we may do. The logical conclusion appears to be, then, to concen- trate all efforts on detailed and comprehensive studies of the properties of these by-products, desirable or undesirable, and to incorporate the results in a rational system of management, rather than to attempt to stop their production. The attitude of American foresters toward these and similar species is undoubtedly changing. There was a tune when they were considered little better than weeds, to be gotten rid of as soon as possible and to be kept out of the forest wherever possible. This concept is giving room more and more to a considera- tion of how best to regulate the unavoidable reproduction of both species and how best to utilize the timber they produce. The so-called inferior or undesirable species have their very definite place in the ecology of the mixed forest, and many examples could be cited from European experience of the disastrous results of an arti- ficial change in representation of species and reduction of the mixed stand to a pure stand composed of an apparently more desirable species, without due consideration to the local soil and climatic condi- tions. Greeley2 seven years ago expressed the opinion that "it is 1 Clapp, E. H. Silvicultural systems for western yellow pine. In Proc. Soc. Amer. Forest., v. 7, no. 2, pp. 168-176, 1912. (See p. 175.) 3 Greeley, W. B. A rough system of management for forest lands in the western Sierras. In Proc. Soc. Amer. Forest., v. 2, no. 2, pp. 103-114, 1907. (See p. 112.) 22 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. both impossible and undesirable to eliminate these species altogether." He specifically names white fir and incense cedar. Their aggressive- ness makes it impossible to eliminate them, even if this were desirable. But more than one species, not so many years ago considered inferior, has now come into its own. The history of the lumber markets of Europe and our own country shows conclusively that with closer utilization necessitated by the growing scarcity of timber, the value of lower grades, as well as of so-called inferior species, is advancing more rapidly than that of upper grades or more valuable species. In the case of incense cedar this evolution may be watched at the present tune. Up to a very short time ago incense cedar was "almost a drug on the market;" now even very short logs when sound are utilized for pencil wood and priced accordingly. Concentration of study on the inferior species, therefore, promises the most immediately applicable results. METHODS OF INVESTIGATION. CHOICE OP SPECIES AND SITE. Forestry is not interested primarily in the morphology and life history of a given heartwood-destroying fungus. Such studies, though indispensable and of the highest value, belong to an altogether differ- ent realm of science. The forester thinks in terms of trees, not of fungi; he concentrates on timber species to be protected or utilized, not on parasitic organisms, however interesting they may be from a mycological point of view. If forest pathology is ever to be of any value to practical forestry, all work and aU conclusions must be focused on the tree, the species, as a producer of timber values and as a member of the forest community. The fact that the same species may be subject to serious loss from several fungi and that the same fungus often works differently in different host trees complicates the difficulties naturally connected with all work for which a basis first had to be constructed. Partly for this reason, the writer first worked on incense cedar, which, so far as known, has only one heartwood parasite, Polyporus amarus. The studies described in the following pages were concentrated on white fir, because its management presents, perhaps, the most embarrassing problem of to-day on the Pacific coast and because, in by far the greater number of cases, serious loss is caused by one fungus only, Echinodon- tium tinctorium. After deciding upon the species to be investigated, the choice of the sites for the study becomes the main question. One single type will probably yield interesting clues, but the result can not with impu- nity be applied to all sites and types within the range of the species. It is clear that studies within what might be termed the merchantable range of the species must be most important from a practical point of view. But inside of the merchantable range the species is subject to FOREST PATHOLOGY IN FOREST REGULATION. 23 so many varying conditions with regard to soil, climate, admixture of the species, and representation that here again typical areas must be chosen for independent studies. The more diversified the types studied and the greater the number of trees per type and in the aggre- gate, the more reliable will be the results. The choice of the particular area to be studied is, of course, impor- tant. The unit of study should be representative, typical for the larger unit. In general it will not be difficult, with some care, to make the proper choice. The result of the writer's studies, still unpublished, on the critical age of incense cedar served to work out the methods which should be applied in a modified form to the at present more important investi- gations on white fir. European precedent could not be used; Martin, Moller, and Hemmann worked on managed forests. New methods to suit our conditions had to be evolved. The only satisfactory result could be expected from careful dis- section and analysis of as large a number as possible of trees of dif- ferent ages. Unlike other investigative work, studies of this kind can not well be carried out on timber-sales areas where the actual felling and bucking of the trees is done by the purchaser. The purchaser is none too willing to cut trees containing rot unless he is compelled to do so; much less does he care to buck such trees, which, after all, are the ones from which we must expect most valuable instruction. He is not obliged to cut trees below a certain diameter limit, which, of course, can not be left out. All this is particularly true for the so-called inferior species, the handling of which often comes so near being a loss to the purchaser that any additional cost would work a distinct hardship. For the same reason it is impos- sible to have the trees on timber-sales areas bucked in odd log lengths, as dictated by the irregular and varying extent of the decay. As will be seen, a few of the notes used for this study are incomplete, because they had to be taken in connection with timber sales. It becomes necessary, therefore, to carry on investigations of this kind on representative areas chosen for the purpose and to have the systematic cutting and dissecting of the trees done by crews, involv- ing much work and a large expenditure. This way of handling the problem has proved to be the only feasible one; and, as long as immediate results may be expected, which if properly applied must lead to very considerable savings as well as to progress in silvicul- tural management and forest regulation, the expense and work seem to be justified. FIELD METHODS. Before the actual felling begins, notes are taken first on the larger forest unit of which the area to be studied forms a part, such as eleva- tion, climate, water table, soil in general, history (lightning and 24 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. forest fires), composition, representation of species, ground cover, possibilities of future logging operations as a first step toward regula- tion, and local valuation of the species; more detailed notes of a similar nature then describe the particular type and stand which is the object of the study. When a new species is to be studied, trees of all sizes and all con- ditions must be cut. It is absolutely necessary constantly to guard against picking out trees either because they appear sound or because they are liable to contain decay. According to the attitude of mind of the investigator there will always be a tendency, conscious or sub- conscious, to think of the final result and accordingly to choose par- ticular trees for felling. The personal factor must necessarily influence the result of the equation and can not be warned against too emphatically. Correctness and accuracy in detail are the basis of any scientific work worthy of the name. Where the one chief aim is to substitute reliable figures for guesswork, to establish facts, from which con- servative interpretation may derive certain working rules, observa- tions and measurements can not go too far in detail and exactness. On the basis of experiences in the incense-cedar studies, a printed sheet was prepared, to be used in a loose-leaf binder of pocket size, in which a set of standard notes was to be entered. Each sheet contains the notes for one tree only. The first notes to be taken on a tree chosen for analysis are general; they are taken before the tree is felled. Slope, exposure, soil com- position, and moisture are taken for the individual tree; the next notes concern the outward appearance of the tree, crown class, as far as can be determined, condition of the bole, whether forked or, leaning, presence and degree of fire scars, resin flow on butt or bole, swellings, sporophores of fungi, condition of the crown, development and state of health; in short, all notes that can and should be taken from the standing tree. During this time an assistant takes the diameter breast high and sets the fellers to work. The notes on the bole and crown are completed when the tree is down. They concern the presence of mistletoes or needle diseases, witches'-brooms of any kind, their number and relative importance, presence and extent of lightning injury, condition of top, and similar data that might have a bearing on the pathology of the species. It goes without saying that the tree is felled at the regulation stump height of 18 inches, never higher unless absolutely unavoidable. The assistant now measures the height of the tree from the ground and counts the age at the stump. This, of course, does not give the true age; but instead of adding, more or less at random, a small number of years corresponding to the height of the stump, it seems advisable to accept the count at the stump as the age. The fewer the figures based on an estimate FOREST PATHOLOGY IN FOREST REGULATION. 25 that are included in our computations, the narrower will be the margin of error. Besides, in practical work, the age is generally counted at a stump height of 18 inches, and, since for all purposes of management we have to deal with the standing tree where diameter is the only indicator of age, it is of little importance whether the age counted is absolute, within narrow limits, as long as all figures are directly comparable with each other. Moreover, in practice it is impossible to have all trees cut at exactly 18 inches. With the greatest of care, the stump height will vary. It is an easy matter, where desired, to add a number of years corresponding to stump height as soon as reliable figures, which now are lacking, are obtainable. The limbs and branches are now lopped off and the brush piled for burning. In the bucking of the bole some judgment should be used, guided by the object of the study. We want to find all traces of decay in the bole and take exact measurements of them. Obviously, then, the aim of the dissection must be to open up the tree in such a way that no decay can escape the observer. It would not do, therefore, to buck all trees in even log lengths of the usual commercial measures. A straight, clean bole without any blemish whatever is bucked in 16-foot logs, which then are individually split; this will, as a rule, bring out any hidden decay. Both the cross sections at the opened surfaces of the split wood must be searched very carefully for any abnormal sign. This makes full knowledge of the properties and aspect of the normal wood a prerequisite. In the beginning, there- fore, it is advisable first to study very closely the sound, normal wood of the species, until the operator is able to detect at a glance and automatically any deviation from the normal. The success of the study hinges upon the development of personal skill in judging wood. In order to prevent the dulling of this sense during the course of the work, check studies of perfectly sound wood will prove very bene- ficial. Any slight real or apparent deviation from the normal hi physical properties or aspect, particularly in color, must be followed, of course, to its source. Trees without any blemish are rare; generally there is either some irregularity in form, fork, unusually heavy branching, or there are sporophores of fungi, badly healed-over branch stubs, swellings, de- pressions, catfaces, fire scars, lightning scars, or frost cracks and frost ridges. In choosing the proper places for bucking, it is generally advisable to start at the most salient malformations or defects; they will often lead to the focus of decay, if there is any. In case of fail- ure, the less prominent defects are investigated, and so on down the line until there is no doubt left that no decay is present in the bole. Particular attention must be given to branch stubs, which, by extend- ing through the sapwood to the outside of the tree, offer an easy 26 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. entrance into the heartwood. After infection has taken place in this manner, the mycelium grows in the heartwood. Before sporo- phores are formed it is often impossible to locate the presence of the mycelium in the tree. This is particularly true for quite young fungus plants, and the possibility that the beginnings of decay may be hidden in a log, both ends of which are perfectly sound, must ever be present in the mind of the operator. It is impos- sible, except by mere chance, to detect the very first stages in the field. As soon as the fungus plant, the mycelium, has reached a certain stage of development, represented by visible alterations of the wood, there is no excuse for overlooking it. As a rule, the oldest part of the focus of infection shows the strongest evidence of fungus growth expressed in what we call decay. Decayed stubs are a valuable index as to decay in the tree, although there are cases where, for unknown reasons, the infection does not, or only very slowly, result in more extended decay. Duesberg 1 has advocated the location of infected trees by the presence of diseased branch stubs. Such decayed branch stubs may also correspond to that stage of development of the mycelium just before the formation of sporo- phores through the stub takes place. In this case also decayed branch stubs will be most valuable in detecting heart rot in the bole. If decay is found, it is followed throughout its entire extent by splitting the logs with wedges and with the ax. To avoid this often very tedious and time-consuming work, splitting with black powder has been tried, with rather unsatisfactory results. In partly decayed logs the splitting is very irregular, and the wood surfaces are badly stained and blackened, the stain generally interfering with the inspec- tion of the wood. When the full extent of the decay is determined, notes are taken on the character of the discoloration or decay and on the stage of development, and the extent is carefully measured. For studies of this kind it will often be sufficient to note the extent in length in linear feet, under the assumption that in low-priced species any lumber that might be cut from an affected part of the bole will not pay for its transportation to the mill. In higher grade species the lateral extent must always be considered. This complete and detailed dissection usually allows the tracing of the decay to some point of entrance, whether fire scar, lightning wounds, frost cracks, or branch stubs. The result is entered on the sheet. Finally, any notes not specially foreseen on the sheet are entered under "Remarks." As a general principle, all observations that can be expressed numerically must be given in figures. It is essential that all esti- 1 Duesberg. Das Aufsuchen von Schwammbaumen in Kiefernbestanden vor der Ausbildung von Fruchttragern. In Ztschr. Forst- u. Jagdw., Jahrg. 44, Heft 1, pp. 42-43, 1912. Reviewed in Forestry Quart., v. 11, p. 251, 1913. FOREST PATHOLOGY IN FOREST REGULATION. 27 mating should be reduced to a minimum. In order to render this unavoidable minimum, which undoubtedly constitutes a source of error, as innocuous as possible, the operator must constantly be on the guard against any variations of his standard by which he is guided, consciously or subconsciously, and from time to time check up on this standard. The notes to be taken by estimate concern degree or grade. Soil moisture, seriousness of wounding by fire, degree of resin flow (whether light or heavy), condition of crown (for example, unhealthy color or thin foliage and the presence and degree of needle diseases in their bearing on the thriftiness of the tree), degree of dis- coloration of the wood — all these can be expressed in figures only with difficulty. Even if a scale of 1 to 10 is adopted for these pur- poses it is extremely difficult to decide whether the change of color of the wood under the influence of the fungus is to be classed as 6 or 7. The writer therefore has adopted a simpler system, which, while far from being exact, at least avoids gross errors and at the same time is graphically clear and sufficiently elastic to cover all cases of impor- tance. It expresses the information asked for on the sheets with the aid of crosses and dashes. A dash after "Fire scars," for instance, is negative; there is no fire scar. One cross, x, is simply affirmative; there is fire injury, but it is not to be considered as serious. Two crosses, xx, indicate that the fire injury is fairly bad, distinctly beyond the mere presence of an injury. Three crosses, xxx, em- phasize the damage; the fire injury is unusually large and severe. By putting the crosses in parentheses, (x), or x (x), or by hyphenating two consecutive degrees, x-xx, intermediate grades may be given when desirable; and finally the last grade, xxxx, can be used in very extraor- dinary cases for emphasis. In general, x, xx, and xxx will answer the purpose. Thus, the estimate is really reduced to a simple system of three grades, which allows for a more constant mental reference to the standard. Whenever necessary or feasible, special notes or meas- urements are entered after the crosses. This system is also used in our tables. With the exception given above, all these notes are taken by the chief of the party. Meantime, the assistant counts the age and diameter at every cross section, takes growth measurements, measures the width of sapwood and the length of the sections, and records such other data as may present themselves hi the course of the work. In complicated cases, drawings or notes are added on blank sheets bearing the numbers of the trees. PATHOLOGY OP WHITE FIR. The studies on white fir presented in the following pages are not meant to give definite results valid for the entire range of the species. They were primarily intended to develop the more practical methods 28 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. to be employed and secondarily to gain reliable material to be used in a chain of similar studies on different types, from which conserva- tive interpretation may derive final conclusions. They are given here as examples only, as illustrations of the general considerations presented in this bulletin. Since making these studies, others on a larger scale and on different types in different parts of the range of white fir were carried out with improved methods during the summer of 1913. A short review of our present knowledge of the pathology of white fir will be of help in the discussion and interpretation of the data presented in this paper. White fir (Abies concolor (Gord.) Parry) can not be called a decadent species; on the contrary, it is very aggressive and possesses remarkable elasticity and resistance to injurious influences. Its tolerance to shade is well known. Not only does it survive dense shading to a high age but it responds readily to light and then reaches considerable diameter and height in perfect health, provided it has not been seri- ously wounded and infected. The oldest tree examined in this study was 258 years old; it was badly suppressed and but 67 feet high with a diameter breast high of 17.4 inches. In the trees tallied between the ages of 130 and 140 years, the diameter breast high varied from 8.8 to 30.7 inches and the height from 47.5 feet to 125 feet. In speaking of tolerance which allows suppressed trees to reach a high age under the most unfavorable conditions and with a minimum of annual growth, the behavior of the species with relation to light is generally meant; but this toning down of the life functions of the tree, visibly expressed in growth, very often has nothing to do with lack of light. A tree may become suppressed to the lower limits of its tolerance by any agent severely attacking any of its vital organs. Of these, the organs of the crown are both most easily accessible and most sensitive; hence, the heavy damage resulting from a serious attack by insects devouring and killing the foliage or by leaf-inhabit- ing fungi. White fir is subject to a disease of the foliage caused by LopJiodermium nervisequium, which often kills all needles except those of the current year's growth. The loss in foliage surface, and therefore in photosynthetic capacity, may suppress a white fir just as lack of light would. Witches' -brooms caused by Peridermium elatinum on white fir are not common. They are very rarely of such development on the tree that they should be classed as an injurious factor to be reckoned with. Incidentally, it should be mentioned that the swellings and cankers so commonly connected with Peridermium elatinum on Abies pectinata in Europe are unknown in Abies concolor. On the other hand, very similar swellings and cankers caused on white fir by Razoumofskya abietina Englm. are extremely common. The FOREST PATHOLOGY IN FOREST REGULATION. 29 actual connection is readily established by either the living mistletoe growing out from the swellings or by the small cuplike remains of the stem bases. The swellings render the affected part of the bole unmerchantable. When they break open into what are termed cankers, infection by fungi very readily takes place and a focus of heart rot forms, very much as in the case of Peridermium elatinum on Abies pectinata where Polyporus Jiartigii and Agaricus adiposus 1 commonly start from cankers caused by the rust fungus. The mistletoe cankers very often are the cause of white-fir stems breaking off in a storm, just as Peridermium cankers affect Abies pectinata. This mistletoe is more generally found in the middle or lower parts of the crown; infection takes place only on the very youngest twigs. Another mistletoe (PJioradendron lolleanum (Seeman) Coville) nests high up in the top. It often kills the leader; volunteers spring up, which are frequently killed in their turn. Considered in its rela- tion to the totality of leaf functions, the loss from a killing of the leaders can not be very serious, although it may count in combina- tion with other injurious agencies. The same is true for the host of minor parasites and injuries to which the peripheral growing parts — in contrast to the column of wood — are exposed. We have seen that the wood of the living tree itself is generally immune to attack from heartwood-destroying fungi as long as it is protected by bark and sapwood. The few exceptions, it seems, are of no great importance in the case of Abies concolor. Pholiota flam- mans is not uncommonly found in white fir and seems to take the place of Armillaria mellea. The exact damage done is still to be studied. Fomes annosus is not yet reported on white fir to the writer's knowledge. Polyporus schweinitzii is not common on the species. All other fungi causing decay can not enter the living tree except through some opening, as far as is known at present. In white fir, as in other coniferous trees, small superficial wounds are readily covered over with resin from the bark ; this natural dressing does not allow fungus spores to germinate or the hyphas to develop after germination. Now, white fir is distinctly poor in resin. Large superficial wounds may therefore prove to be more serious. If the bark is destroyed, the cambium is killed and the sapwood dries out and cracks. Through these cracks air gains access to the interior of the tree and must in some way alter the chemistry and physics of the heartwood. The spores of heartwood-destroying fungi lodge in the cracks and upon germination may find a well-prepared substratum in the heartwood. Fungi, like all plants, make certain specific demands as to the chemical composition, water content, oxygen, etc., of the substratum they live on. Given the proper temperature 1 Hartig, Robert. Lehrbuch der Pflanzenkrankheiten. Ed. 3, p. 153. Berlin, 1900 30 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. and the species of wood on which, for instance, a fungus like Echino- dontium tinctorium (Indian-paint fungus), the most common de- stroyer of white-fir heartwood, can exist, its growth will still be dependent on the presence of heartwood of a certain character and on the water content of the heartwood. This is evidenced by the fact that decay is so commonly found in concentric development at a certain distance from the sapwood. The heartwood contains water in varying degrees, although it does not lift water like sapwood. But there is nothing surprising or irrational about the assumption that the water content of the heartwood will depend more or less on the water movement in the sapwood. The water in the heart- wood of conifers is found in the membranes of the tracheids, not in the lumina. In a normal sound tree, heartwood of a given age and diameter surrounded by sapwood of normal width, corresponding to a certain crown development, will contain approximately a standard amount of water. Decrease in crown activity through some cause or another (suppression, injury to the crown, etc.) will soon be expressed in a rapid progress of heartwood formation, leaving only a narrow strip of sapwood, through which very much less water will move upward to the crown than in the normal tree. We may safely assume that the water content of the heartwood will change to a certain degree with the amount of water moved upward in the sap- wood. The water content of the sapwood changes, furthermore, with age, and also with the season. Both changes must also appear, although in a far less degree, in the heartwood. Munch 1 has em- phasized, in a series of very interesting papers, the relation of wood- inhabiting fungi to the water and air content of the host tissues. Water-logged tissues are inaccessible to these fungi; a certain mini- mum of air, as Munch expresses it, must be present in the tissue in order to allow the development of the hyphae. Variations in the water contained by imbibition in the cell mem- branes must influence the degree of humidity of the air in the lumen of the cell itself; it is quite probable that this factor also plays a role in the distribution of hyphse in the wood. What percentage of water in the cell membranes and of air in the lumina of the heartwood presents the optimum for the development of Echinodontium tinctorium and other similar fungi we do not know; but evidently there must be an optimum, a maximum, and a mini- mum. Any factor influencing the quota of water and air in the heart- wood must, therefore, be of great importance. Cracks in the sapwood i Mtinch, Ernst. Die Blaufaule des Nadelholzes. In Naturw. Ztschr. Land- u. Forstw., Jahrg. 5, 1907, Heft 11, pp. 531-573; Jahrg. 6, 1908, Heft. 1, pp. 32-47, 33 figs.; Heft. 6, pp. 297-323. Munch, Ernst. Untersuchungen fiber Immunitat iind Krankheitsempfanglichkeit der Holzpflanzen. In Naturw. Ztschr. Forst- Land u. w., Jahrg. 7, 1909, Heft 1, pp. 54-75, 5 figs.; Heft 2, pp. 87-114; HeftS, pp. 129-160. Miinch, Ernst, tiber krankhafte Kernbildung. In Naturw. Ztschr. Forst- u. Landw., Jahrg. 8, 1910, Heft 11, pp. 533-547; Heft 12, pp. 553-569, 2 figs. FOREST PATHOLOGY IN FOREST REGULATIOK. 31 reaching to the heartwood admit air, and by evaporation change the water content of the heartwood ; by oxidation, changes in its chemistry probably also take place. The change must necessarily be intensified, the more serious the injury. Wounds exposing the heartwood heal over very slowly, and the heartwood which receives all its water from the sapwood must be modified very markedly in its chemistry and physics, particularly in its water and oxygen content, by the long exposure to the air. More- over, from the time the injury happened until the time the wound is completely healed the heartwood is directly exposed to inoculation from spores of wood-destroying fungi adapted to white fir. Although the production of spores by a sporophore is enormous, by far the greater number are carried by air currents to places where they can not germinate for lack of moisture; many are intercepted by the natural screen (" forest screen") formed by the foliage and trunks of uninjured trees or by trees to which they are not adapted, and only a very small number finally land in the cracks of exposed sapwood or on exposed heartwood of white fir of the proper age. Of these, again, a very small percentage find temperature and moisture favorable for germination. This explains the fact that so many trees, although badly wounded, are not infected. But it stands to reason that every year during which the heartwood remains exposed adds to the danger of the tree becoming infected. By far the deepest wounds are caused by fire. Although in white fir the danger in repeated fires feeding on the pitch flow following a first injury is comparatively slight, and although the lack of resin in the wood does not favor the hollowing out of the interior of the tree as it does in yellow pine, fire frequently causes very long wounds, which reach into the heartwood. Spores can gain entrance to the heartwood through open frost cracks. Low temperatures and sudden drops of temperature are common throughout the range of white fir. Inside of the range they are more or less confined to certain localities and zones. Lightning in white fir generally causes more or less superficial wounds. The peculiar injuries to be traced to lightning in white re- present many interesting features. Here we are only interested in injury which might lead to the infection of the heartwood. As in yellow pine, lightning sometimes tears long strips of bark off the tree and leaves the cambium and sapwood unprotected. In such cases both die and dry out, with the result that cracks in the sapwood lead into the interior of the tree. Smaller superficial lightning wounds locally kill the sapwood, which is very commonly attacked by second- ary fungi, which do not do very serious damage. However, logs with lightning injury of this kind are liable to be thrown out as culls, although they generally contain some sound heartwood. 32 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. Other causes of serious wounds are comparatively rare. Occasion- ally a falling tree will brush off part of the bark of its neighbor. If the wound is large, the exposed sapwood dries out, cracks, and the heartwood becomes exposed. Very rarely a living tree shows signs of early girdling by rodents. Girdled trees as a rule are killed within a short tune. With very few exceptions the entrance of the fungus into the tree can be traced to one or more of the wounds just discussed. Occa- sionally, however, a tree showing no wounding at all is found to be decayed. In such cases the only means of entrance for the wood- destroying organism is through knots. White fir prunes itself very poorly; the wood of the twigs is tough, hard, and resistant, and the branches do not break off very readily. Later, dead twigs may break off; in the cracks of the wood of the stubs spores of fungi may find proper conditions for germination and, once established, use the pin knot as a bridge from the exterior of the tree through the bark and sapwood into the heartwood. This is par- ticularly true for twigs in which heartwood formation has begun. In this sense the opening afforded to fungi by a pin knot that is not healed over may be likened to a wound. The opening formed by the pin knot, however, is too small to materially influence the chemistry and physics of the heartwood of the tree. White fir is not exposed to a great number of heart-rot fungi. Polyporus schweinitzii is not common. Polyporus sulphureus and Trametes pini are rather rare. The parasitism of Fomes pinicola is not fully established, at least not in white fir. The writer has found it on thrifty sugar pine in central California, where it was undoubt- edly parasitic in the sense of attacking the sound heartwood of living trees through an open fire scar and extending toward the sapwood. There would be no incongruity in assuming that it may also occur parasitically on white fir; in fact, a number of observations rather speak for the correctness of this assumption. By far the most serious danger to white fir throughout its range comes from Echinodontium tinctorium Ellis and Ev. This fungus seems to be particularly adapted to Abies concolor and does not appear on many other species. In California it is, though not very often, found on Abies magnified sJiastensis and also rarely on Douglas fir. This fungus must therefore be considered as the chief fungus enemy of white fir. The sporophores are easily recognized. They are rather large, from 2 to 10, 12, and more inches in width (measured horizontally from side to side where they are attached to the tree), distinctly hoof shaped, with a black, dull, cracked, rough upper sur- face, and a lighter, grayish, level under surface, which is thickly set with hard, coarse spines. In young specimens the under surface is whitish and rather daedaloid prior to breaking up into spines. The FOEEST PATHOLOGY IN FOREST REGULATION. 33 interior of the sporophore is vividly rusty red. This rusty color is most characteristic of the fungus and repeats itself very often in the decayed tissues of the host. The sporophores are never formed on the bark of the tree; invariably they appear from the under side of stubs of dead twigs or branches, and commonly the rusty color can be followed through these stubs or knots. As the sporophore is nothing but the fruiting body of the mature fungus plant living in the heartwood of the tree, which alone it is able to attack, every sporophore is a certain sign of far-reaching decay in the tree. The typical rot may be characterized as a stringy brown rot. Wood in this stage of decomposition is brown, with rusty reddish streaks, and becomes distinctly fibrous and stringy. Following the rot away from its maximum of development, we find wood still brown, with rusty streaks, but quite firm. Farther away, the brown color becomes less noticeable, the rusty color disappears, and finally we come to a point where the wood seems to be sound enough to be sent to the mill. A little care exercised in examination, however, will show in this seem- ingly sound wood the presence of small light-brownish spots and dis- colorations, particularly in the summer wood, intermingled with hor- izontal burrows, which at first glance could almost be taken for very shallow insect burrows. The burrows are not easily detected on a cross section. The small brown spots, which give the wood a faintly brown, mottled appearance, cause the entire cross section to be slightly darker than normal and discolored; but they show up very much more clearly in a longitudinal section. A small piece pried out of the end of the log with a hatchet or strong knife gives sufficient informa- tion about the real state of health of the log. This timber at present invariably goes to the mill and without doubt furnishes the lumber that, after being sawed, dries out and by becoming brittle causes the well-known prejudice against this species. It is often characterized by a peculiar sour smell and by a spongy consistency of the wood. Cull from decay in white fir, therefore, includes not only typical rot but also this discolored material, which, although not distinctly rotten, is already under the influence of the advance guard of the fungus mycelium and will become completely decayed later on. For this stage of incipient, or, better, latent decay, the writer proposes the term " advance rot," which is used throughout this bulletin. DESCRIPTION OF AREAS. The three areas chosen for investigation are located on the Crater National Forest, in southwestern Oregon, all of them in the neighbor- hood of the Upper Klamath Lake, a large shallow basin with vast swamps, into which unusually large springs of clear cold water empty themselves. Very few streams of running water come from the 98035°— Bull. 275—16 3 34 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. I surrounding mountains. Dense timber frames the swamps and ex- tends up the slopes to the mountain tops. The elevation of all three tracts varies from 4,150 to about 4,400 feet. Low winter tempera- tures and severe lightning storms are frequent in the entire region. Two of the tracts, the Pelican Bay Lumber Co. sales area and the Odessa ranger-station tract, are situated on the west shore of the lake. They are about 2 miles apart and present conditions so much the same that they can be considered as one. The Pelican Bay tract on the west side of Pelican Bay lies, as far as the area covered by this study is concerned, along the slopes; the aspect is east to northeast. That is, it is exposed to cold wintry winds, sweeping unbroken across Upper Klamath Lake. We may expect frost injury. The volcanic soil is fairly deep and loose; the humus layer is rather shallow. There are no rock outcrops. The underbrush is composed of Ceanothus, manzanita, and some chin- quapin. The Odessa ranger-station tract is far less steep than the Pelican Bay tract. A considerable part of it is a gentle slope, almost level. The general aspect is north; presumably the tract is less exposed to sweeping winds of very low temperature. The soil is decomposed lava, but richer in humus than the Pelican Bay tract. Outcrops of rock are frequent. There are a number of large springs in the neigh- borhood. The underbrush is rather dense and is composed of Amelanchier alnifolia, Ceanothus velutinus, with some Salix sp.; the ground cover consists of Ceanothus prostratus, Berberis aquifolium, and Symphoricarpus racemosa. The third tract, the Otter & Burns sales area, lies about 15 miles north of the north end of Upper Klamath Lake. The tract is level, the soil very loose, sandy, decomposed pumice, with no indication of rock. Under the influence of the Fort Klamath Valley with its swamps, the atmospheric humidity is rather high, as is evidenced by the rich lichen flora, Alectoria fremontii being common. Thus the immediate surface of the soil is kept damp, and litter disintegrates very rapidly. The humus is about 1 to 2 inches deep; the soil imme- diately underlying it is remarkably well drained. The rapid humifi- cation in the top layers favors the development of mycorrhiza on the roots of white fir in surface strata. White fir seedlings show a thick matting of mycorrhiza, confined to the same strata of a certain humi- fication, and a very long taproot seeking water. Yellow-pine seed- lings also develop a taproot, but the mycorrhiza rootlets are found at a greater depth than those of white fir. They are not as closely bunched as in white fir and are distributed over a larger area in a vertical direction. The underbrush is formed by Ceanothus velutinus of medium density, from 4 to 6 feet high, in a uniform cover. FOREST PATHOLOGY IN FOREST REGULATION. 35 On the two tracts near the lake white fir is mixed with yellow pine and Douglas fir, a little incense cedar, and a very little sugar pine. On the Otter & Burns tract the stand is composed of yellow pine and white fir, with occasional lodgepole pine. On each tract conditions were more or less uniform, differences in elevation were negligible, and neither deep gulches nor steep slopes had to be figured with as disturbing factors. All in all, 160 trees were dissected and notes taken on all factors which possibly would have some bearing on the subject of this bulletin. In operating, the tracts were not clean cut; that is, not every white-fir tree in the area was felled and examined, since it was not the object of the study to estab- lish a cull per cent for that particular region. The data obtained are from selected trees. On the Pelican Bay Lumber Company's sales areas the trees, of course, had all been marked by the Forest Service officers in charge; on the Otter & Burns sales area some trees were marked, and others were felled inde- pendently of marking. On the Odessa ranger-station tract all trees examined were felled for our special purpose. The representation of trees of different ages, diameter, and height classes on the three tracts, therefore, is not expressed correctly by the number of trees examined on each tract. LOCAL PATHOLOGY OF WHITE FIR. The pathology of white fir in the Upper Klamath Lake region is comparatively simple. Of injurious factors of an inanimate nature, fire, lightning, and frost are common. Very few species of fungi inhabiting living white fir are found on the three tracts. As we are mainly interested in the pathology of the the wood, the occasional occurrence of Peridermium elatinum and of LopJiodermium nervisequium becomes an entirely negligible factor. Of heartwood-destroying fungi in living white fir, EcJiinodontium tinctorium is by far the most common, and sporophores are numerous. About 75 per cent of all cases of decay were due to this fungus. Occasionally decay may with some certainty be traced to Fomes pinicola. In one case a sporophore of an Irpex was found in the decayed hollow of the trunk. Trametes pini is missing altogether, though found occasionally on neighboring sugar pine. Decay caused by Polyporus schweinitzii was found in several cases, never with sporophores. In other cases the decay was too indefinite to allow an identification of the fungus causing it. This is particularly true for the many cases of localized advance rot connected with scars from diffused lightning. The preponderance of EcJiinodontium tinctorium, especially in con- nection with really damaging decay, is so marked that in this study all important cases of decay are considered to be caused by this fungus. 36 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. A study of the fungi destroying down timber lies beyond the scope of this bulletin. The only practical aspect of their activity lies in the fact that down timber, limbs, branches, twigs, and needles are decom- posed very rapidly. It is evident that all the points discussed in the preceding pages must be kept in mind in taking field notes. But this is not sumcient. Work of this kind has very much the character of an exploration; surprises and discoveries are possible at any point of the road, and it is therefore indispensable constantly to be on guard in order not to overlook any phenomenon wortky of observation. TABULATION OF DATA. The next step is proper tabulation of the data obtained. The three tracts were so close together and conditions so similar that they were considered as one, and all notes were combined. Separate interpreta- tion of the notes of each tract showed differences only in detail. The procedure was as follows: A first table was compiled from the field notes giving all important data as well as all such data which might have a bearing on the subject of this bulletin. As we are particularly interested in the problem of the relation of age to infection and subsequent decay, a second table gave the same notes arranged progressively by the ages of the trees examined. This table formed the basis for further operations. The youngest tree dissected was 60 years old, and it is the first to show decay (Table I). The possible age limit of infection is therefore at least 60 years; it is probably lower. But in practical forestry we do not seek an answer to the question of the earliest age at which a tree might become infected, interesting as this is from a mycological point of view, but, rather, from what age may we with reasonable certainty assume that serious decay becomes so prevalent as to distinctly impair the merchantability of the timber. The tree in question has a diameter breast high of 10.1 inches; it is 44 feet high. A healed-over broad scar still visible externally at 2 to 8 feet above ground corresponds to an internal scar, reaching from 2 to 10 feet, and was probably caused by lightning. The injury happened 22 years ago and was distinctly superficial; the deterioration, in the form of a slight discoloration of the sapwood, follows this scar only, without extending any farther into the wood. This superficial dam- age does not render the affected logs unmerchantable. For practical purposes, therefore, such cases may be disregarded; they are negli- gible. In the interpretation of our material, the character and the degree of the damage must be considered with special relation to their bearing on the merchantability of the lumber. Not only the extent in longitudinal direction but also the distribution of the decay over FOREST PATHOLOGY IN FOREST REGULATION. 37 the cross section enter into the valuation of this factor. In the present study, the lateral extent of decay, the distribution over the cross section, was estimated, as it is in practical scaling. Actual measure- ments are difficult to take, on account of the immense variability of the decay. In Table I, decay which neither in lateral extent nor hi degree was considered sufficient to seriously injure the merchanta- bility of the part affected was marked as negligible. The longitudinal decay was taken in linear feet, and the entire length was considered as affected, in order not to complicate the computation too much. We must distinguish between superficial decay of the sapwood and the more serious decay of the heartwood. Figures of superficial decay of sapwood are given in brackets (Table I, column 5) . The next trees are sound. A negligible decay occurs in a tree 73 years old. Its diameter breast high is 11.2 inches; its height 58 feet. The light decay started from an internal scar, caused by fire 23 years ago and healed over in 5 years, but it remained in close proximity to the scar without spreading. Again, a number of sound trees fol- low. Then the first more serious decay appears. The tree in question is 84 years old, its diameter breast high only 8 inches, height only 45 feet. Both fire and lightning have played havoc with this individual. An open scar extends from the ground 21 feet up the bole. The tree is quite evidently not in good health, the sapwood is very narrow, and the crown is lopsided and very short. Even in this case the decay follows more or less the open scar, but it is sufficiently serious to cull the affected parts in so small a tree; in a larger and thriftier one the damage would be called more or less local and a nominal deduction made in the scale. From a lumbering point (of view this tree may be disregarded. So far, all trees considered had been either thrifty or not very seriously wounded. Here we have an obviously suppressed, un- healthy, and badly wounded tree; it presents at the same time the first case of decay that is not to be called negligible. The following trees are sound ; then follows a negligible trace of decay in an 86-year- old tree, badly suppressed (diameter breast high 4 inches, height 13 feet), grown in dense shade, with a remarkably small crown and with a healed-over frost crack, but no other wounds. After several sound, fairly thrifty trees foUows a tree 87 years old, badly suppressed (diameter breast high 7.8 inches, height 39 feet), with a very short crown, wounded badly by fire and lightning (open scar from ground to 18 feet) , and with decay following more or less closely the open scar. From these and the following trees, it appeared possible that with increasing age the crown class, or rather the degree of suppression and dominance, played a role with regard to the extent and seriousness of the decay. Preliminary studies on incense cedar had given the same indications. It seemed desirable, therefore, to express this degree of 38 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. suppression and dominance by a figure which would allow direct com- parison between trees of the same age. Height alone would be mis- leading. Volume table figures can not be used, since they are based on sound normal trees. The relation of height to diameter breast high, expressed in total volume, was thought to be a safer index. The object being to obtain directly comparable figures by ages and not the exact volume, the tree was considered as a perfect cone over the stump, at which we had taken the ages. From somewhat scanty, but individually reliable notes, the diameters at the stump (diameter outside bark 18 niches) were obtained, and from these and the height the volume of the cone in cubic feet was computed. TABLE I. — Fundamental data on the pathology of the white fir. No. of tree. Age. Volume (cubic feet). Character of wounds. For each tree. Average for trees of same age. Of rot, in- cluding ad- vance rot (percent- age of total volume). 1 2 3 4 5 6 136 60 69 71 72 72 73 76 78 80 81 82 84 84 84 85 86 86 86 87 87 87 87 90 92 92 94 96 96 96 96 101 102 103 103 104 104 104 105 105 105 105 105 106 106 107 11.3 25.1 11.8 18.8 7.7 18.5 23.0 12.4 31.4 45.5 29.9 44.4 8.9 25.6 7.5 33.7 6.3 22.8 13.3 27.1 6.8 9.6 30.1 128.1 10.2 44.8 38.1 32.9 25.1 25.1 46.5 22.3 34.2 35.2 25.5 25.5 68.2 20.7 90.3 32.2 58 52 29 48.3 17.0 15(?) 19 20 20 20 20.3 21 21.3 23 24 24.1 24.6 24.6 24.6 25 26 26 26 26.5 26.5 26.5 26.5 29 30 30 31 32.5 32.5 32.5 32.5 37 38 39 39 40 40 40 41 41 41 41 41 42 42 43 M34.2] 12.7 82.8 Negligible. 82 19.9 "[4.53] 55.3 13.5 16.8 61 [2.39] 71.8 47.6 43.5 46.9 Traces. 45.5 Lightning. Leader healed in. No wounds. Very slight lightning. No wounds. Fire; healed. Lightning. Very little lightning. Do. Several scars. Lightning (?). No wounds. Fire, open; lightning. Little lightning. No wounds. Little lightning. Frost ridge. No wounds. Ligthning. Very little lightning. Lightning with fire. Fire; healed. Fire, healed; lightning. No wounds. Very little lightning. Fire, open; lightning. Fire, open. No wounds. Fire, open. Lightning. Do. Fire, open. Fire; lightning. No wounds. Lightning. Do. Old girdling; lightning. Fire, open. No wounds. Do. Do. Do. Fire, open. Lightning. Falling tree. 105 145 135 147 143 159 111 134 139 138 89 125 130 133 137 144 146 148 149 124 129 88 90 128 103 122 127. 76-a2 76-b 2 21 120 132 46 72-a 72-b 158 126 18 20 45 87 . 102 121 68... 1 The use of brackets ([ ]) in column 5 indicates superficial decay of sap wood. 2 The letters a and b indicate two distinct foci of decay in the same tree. FOREST PATHOLOGY IN FOREST REGULATION. 39 TABLE I. — Fundamental data on the pathology of the white fir — Continued. No. of tree. Age. Volume (cubic feet). Character of wounds. For each tree. Average for trees of same age. Of rot, in- cluding ad- vance rot (percent- age of total volume). 1 2 3 4 5 6 80 107 107 107 107 108 109 110 110 110 110 110 110 111 111 112 112 112 113 114 116 116 118 118 119 119 121 122 123 123 123 124 124 124 125 125 126 129 130 130 131 132 132 132 133 133 134 135 135 136 136 136 137 137 138 138 140 140 140 140 140 140 140 141 143 144 146 146 148 148 149 150 40.6 39.6 65 55.0 61.2 33.8 30.0 47.7 14.7 72.6 24.8 26.8 32.1 14.6 66.2 40.8 40.7 25.7 30.3 11.7 36.3 11.5 20.5 89.5 37.6 18.9 46.3 39.5 18.5 21.8 141 21.3 30.5 53.5 125.5 42.7 85.6 32.8 52.3 14.3 87.4 256.5 98.2 90.2 26.4 28.8 55.1 83.2 9.9 108 86.4 49.1 33.6 77.4 76.3 54.4 187.0 20.6 24.3 50.4 28.2 136.5 51.1 35.0 235.5 94.5 30.0 135.5 154 34.1 66.5 43 43 43 43 44 45 46 46 46 46 46 46 47 47 48 48 48 49 50 52 52 53.5 53.5 54 54 56 57 58 58 58 59 59 59 61 61 62 65 66 66 67 69 69 69 70 70 71 73 73 74 74 74 76 76 78 78 80 80 80 80 80 80 80 82 86 87 90 90 94 94 96 97 [92.2] [97 12] 68.5 58.7 23.7 42.9 42.1 61.5 [23.9] [Trace.] 40 100 89.0 M 29.0 60.0 Negligible. 58.1 82.1 80.3 77.5 32.4 93.7 65.3 34.6 21.8 42.0 60.7 95.6 76.9 85.3 96.4 132.7 100 00 133.5 00 51.2 [27.7 88] 70 60.1 Lightning. Little lightning. No wounds. Frost crack. No wounds. Do. Fire, open. No wounds. Fire, open. Do. Little lightning. Very little lightning. Fire, open. Fire; little lightning. Twin healed in; frost crack. Fire, open; lightning. Frost crack. Fire, open. Fire; lightning. Fire, open. Do. No wounds. (?) Fire. Fire; lightning. Lightning. Little lightning. Frost crack. Lightning. Fire, open. Fire. Frost crack; lightning. Fire, open; lightning. Lightning. Fire, open. Frost crack. Fire, open; frost crack. Lightning. Fire, open. Frost crack. No wounds. Do. Frost crack. Fire, open. Lightning. Do. No wounds. Fire; frost cracks; lightning. Frost crack. No wounds. Do. Do. Lightning. Do. Frost crack. Fire. No wounds. Lightning. Lightning, severe. Lightning. Fire, open: lightning. Fire. open. Do. Falling tree; frost crack; lightning. No wounds. Fire. Frost crack; lightning. Frost crack. No wounds. Fire, open. No wounds. 123 19 ... . 44 23 62 100. 22 75 . 78 108.. 110 104 131 94 99 37 96 101... . .... 97 109 98 140 40 74.. 115 150. 58 69 154 38.. 56 113.. 33 41... 60 79.. 54 63 . 65 17 30 49 42 112 53 . . 28 55 26 16... 48 . 1 50 2 15 6... 7 70 119 153 155... 43 156 61.. .. 11 4 106. .. 5. 35 92 10... 40 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. TABLE I. — Fundamental data on the pathology of the white fir — Continued. No. of tree. Age. Volume (cubic feet). Character of wounds. For each tree. Average for trees of same age. Of rot, in- cluding ad- vance rot (percent- age of total volume). 1 2 3 4 5 6 25 150 150 150 151 152 152 155 155 155 156 156 159 160 160 161 161 162 163 163 164 165 165 166 166 168 169 170 170 170 175 175 178 178 180 183 185 185 186 189 191 192 200 200 221 232 258 123.5 45.6 112.5 16.6 192.5 75 235 121 37.7 380 96.5 152.0 224.5 26.8 68.6 68.2 38 122.5 106 417 (?) 128.5 57.2 171.5 179 291.7 328.5 121 123. 8 68.0 68.0 212.7 127.7 133 100 148.3 100.5 42. 85 64.4 546 110.7 115.7 26.0 196 235 46.7 97- 97 97 99 101 101 107 107 107 109 109 109 116 116 118 118 121 123 123 125 127 127 129 129 134 136 138 138 138 150 150 158 158 164 166 166 166 166 168 168 170 180 180 190 200 220] 81.5 55.5 68 41.3 58.1 15.7 63.2 36.2 Negligible. 36.5 32.8 73.7 98.5 89.4 82.9 25.5 Incomplete. 53.4 (?) 6.8 53 87.4 67.2 47.1 16.4 [5.1] 16.7 39.5 53.6 52 95.5 Negligible. 100 100 71.3 [100] Frost crack. Fire, open; lightning. Do. (?) Frost crack. Do. Fire, open. Do; Lightning. Fire; frost crack. Do. No wounds. Fire, open. Fire, open; lightning. Lightning. Frost crack. Lightning. Notes missing. Fire, open. Frost crack (healed); lightning. Fire, open. Fire; lightning. Notes missing. No wounds. Fire. Fire; frost cracks. Fire. Frost crack. No wounds. Fire, open. Lightning. Frost crack. Lightning. Fire, open. Lightning. No wounds. Fire, open. Lightning. Frost ridge; lightning. Fire. Fire, open; frost cracks. Frost crack. Fire, open; lightning. Frost crack; lightning. Lightning. Fire, open; frost cracks; lightning. 114 157 . 151 85 g 13 31 117 83 91 27 ... 12 93 118 160 116 47 81 84 3 51 24 32 29 82 8 57 67 64-a 64-b 36 52 77... 71... 34 . 95 107.. 66 39 86 14 142 73 59 141 These volumes are, of course, not directly comparable with each other; they have a meaning only when individually compared with normal volumes for the same age. It was necessary, therefore, to curve data collected on normal trees, such as were selected for vol- ume tables in larger numbers on the same area. The most reliable portion of this curve lies between 80 and 180 years. The relation of the actual to the average volume of trees of the same age we may use as an index of suppression or dominance of the individuals in question. The volume of the decayed part of the bole was figured as the affected part of the cone. But instead of giving the decay simply in FOREST PATHOLOGY IN FOREST REGULATION. 41 cubic feet, making constant reference to the total volume of the tree necessary, the volume of the rot was expressed in percentage of the total volume. Advance rot — that part of the wood already under the influence of the mycelium — is included. It must be kept in mind that all figures given under this heading (column 5) are therefore likely to be high. To be on the conservative side, all measures of decay were taken very carefully, and in all cases where there was any possible doubt the uncertain part was measured as decay. But since the same procedure was followed consistently the results are directly comparable. Table I gives us our working material in figures. Column 1 shows the individual number of each tree from the field notes and is given only for convenience of reference, the trees being arranged in the order of their ages (column 2). Column 3 shows the actual or total volume in cubic feet of each tree, considered as a perfect cone. Column 4 gives the volume in cubic feet for the average tree of the same age. Column 5 shows the volume of rot (including advance rot) in cubic feet expressed as a percentage of the total volume of the tree. Column 6 shows the character of the wounds. CONDENSATION OF DATA. It proved difficult to interpret intelligently this mass of figures. If there existed any relation between decay and possible influencing factors, it certainly did not appear very clearly from this table. It became necessary to simplify and condense the material. Instead of expressing dominance or suppression by the relation of the actual to the normal volume in figures, the system of crosses described above for the field notes was used. Three classes were adopted — dominant, intermediate, and suppressed. Those volumes which came closest to the average were considered intermediate and entered in the table with one cross, which expresses the affirma- tive; a dash signifies negation. In the intermediate class therefore there can be not more than one cross. The deviation from this average shows in the two other classes, and as here all degrees are possible, the degree of suppression or of dominance is shown with one, two, or three crosses. Thus, three crosses under " Dominance" mean that the tree is as far beyond the average as is possible in that locality. On the other hand, one cross under " Suppression" means that the tree is decidedly suppressed, two crosses that it is badly suppressed, and three crosses indicate the highest degree of sup- pression. This classification is admittedly arbitrary; it seemed to answer the purpose, however, and has so many advantages, with its possible grades and its graphical clearness, that it may be retained until some better method is devised. (Table II, columns 3, 4, and 5.) 42 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. To reduce the figures in column 5 of Table I to simpler symbols was more difficult. Here the entire affected part of the cone for practical purposes was considered as cull, including the sap wood. In reality, there are, of course, all gradations from a slight discolora- tion of the sapwood following a long lightning scar or a number of smaller scars to complete destruction of the heartwood by decay. In order to simplify this column and to bring out more forcibly its relation to influencing factors, the writer tried to reduce the percent- age figures to ratings, applying the system of crosses used throughout this study, taking into account ftot only the volume percentage of rot in cubic feet, but also the character of the injury with regard to the degree of rottenness. Thus, one cross in parentheses, (x), signifies slight and negligible local discoloration; one cross (not in parentheses) shows distinct rot, but affecting not more than about one-third of the tree; two crosses, about two-thirds of tree affected; three crosses, more or less of the entire tree affected. In each case, the character of the decay as indicated by the detailed field notes was given due consideration. This explains apparent discrepancies between decay rating and decay volume in the percentages in Table I, where the affected part of the bole was considered as cull for the entire length of the decay. In decay rating, the actual loss in merchantability was expressed according to the character of the rot and its extent. This valuation of the decay, it is true, is necessarily somewhat arbi- trary. It is really the condensation of carefulty taken field notes and measurements and must serve until a more satisfactory method can be found. Where general relationships only are concerned, as in this case, our symbols may be sufficiently correct, provided they are based on exact figures and reliable field notes. (Table II, column 6.) In order to insure a higher degree of reliability for the decay-rating symbols, the operation was repeated some time later without con- sulting the results of the first. With insignificant exceptions, both ratings were identical. In much the same way the character and degree of wounding was reduced to a system of crosses. Plainly, this can be done only from field notes, which were generally amplified by actual measurements of the size and extent of the wound. The chances of inoculation offered by a wound decide its rating. That deep wounds, particu- larly such as have remained open for a longer time, are rated higher than small superficial injuries, soon healed over, is self-evident. The system of crosses is the same as heretofore explained. (Table II, col- umn 7.) The next column (Table II, column 8) indicates the means whereby the fungus entered the tree, as evidenced by the analysis. FOREST PATHOLOGY IN FOREST REGULATION. TABLE II. — Condensed data on the pathology of the white fir. 43 No. of tree. Degree of dominance or of suppression. Decay rating. Wound rating. Infection traced to— Appar- ent condi- tion of crown. Remarks. Age. Domi- nance. Inter- medi- ate. Suppres- sion. 1 2 3 4 5 6 7 8 9 10 136 105 145 135 147 143 159 111 134 139 138 89 125 130 133 137 144 146 148 149 124 129 88 90 128 103 122 127 76-a 76-b 21 120 132 46 72-a 72-b 158 126 18 20 45 87 102 121 68 80 123 19 44 23 62 100 22 75 78 108 110 104 131 94 99 37 96 101 60 69 71 72 72 73 76 78 80 81 82 84 84 84 85 86 86 86 87 87 87 87 90 92 92 94 96 96 96 96 101 102 103 103 104 104 104 105 105 105 105 105 106 106 107 107 107 107 107 108 109 110 no 110 110 no 110 in in 112 112 112 113 114 XX XX XXX XX XXX X XXX X X XX XX XXX X X XX XX XX XX X X X X X X X X X X XX X XX X XX XXX XXX XXX X XX XXX XXX XX XX XX XX X X XX XX XX XX XXX XXX X X XX XXX XXX XXX XX XXX X X XX XX - XX (x) XX X XX X XXX X XX XX XXX X XX XX XX XXX XXX XX XXX XXX XXX xxx XXX xxx xxx xxx xxx XX XX xxx XX xxx xxx X xxx xxx xxx xxx X Lightning (x) x) X X X X X X 8 (x) X xxx (x) X (x) xxx $x x (x xxx X X (x) X X X X X X X (x) X XX XX (x) X X X X X XX X XX X X X (?) X X X X (x) (x (x X (x) X XX X X X Negligible; advance rot. Negligible. Advance rot. Negligible. Advance rot. Do. Advance rot. Open 22 years. Advance rot. Do. Almost completely girdled 82 years ago; wound open 31 years; mostly advance rot. Negligible. Advance rot. Advance rot local- ized in scars. Negligible. Mostly advance rot. Rot following two very long open scars. Advance rot. Very slight advance rot. Slight advance rot. Do. Little typical rot. Fire — Fire; lightning. Frost crack Lightning; fire. Fire XX — X X Fire open — Fire open . XX X Lightning Fire open XX Fire .. Lightning X XX XX do. . Girdling. . Fire open . . Fire open ...... XX X X Lightning Falling tree Lightning Frost crack — Fire open X Fire, open . XX Fire, open Twin and frost crack. Lightning Frost crack Fire, open X X X X 44 BULLETIN 275, U. S. DEPARTMENT OF AGKICULTURE. TABLE II. — Condensed data on the pathology of the white fir — Continued. No. of tree. Age. Degree of dominance or of suppression. Decay rating. Wound rating. Infection traced to— Appar- ent condi- tion of crown. Remarks. Domi- nance. Inter- medi- ate. Suppres- sion. 1 2 3 4 5 6 7 8 9 10 97 109 98 140 40 74 115 150 58 69 154 38 56 113 33 41 60 79 54 63 65 17 30 49 42 112 53 28 55 26 16 1 48 1 50 2 15 6 7 70 119 153 155 43 156 61 11 4 106 5 35 92 10 25 114 157 151 116 116 118 118 119 119 121 122 123 123 123 124 124 124 125 125 126 129 130 130 131 132 132 132 133 133 134 135 135 136 136 136 137 137 138 138 140 140 140 140 140 140 140 141 143 144 146 146 148 148 149 150 150 150 150 151 XX XXX XXX X XX XXX XX XX X XX XXX XX XXX XX XXX XX X X X X X XXX XX XXX XXX XX XXX X XX XXX XXX XXX XX X XX XXX XX XXX XXX XXX XX XXX XX XXX XXX XXX XXX XX XXX XXX XXX XXX XXX XX XXX XXX X XX .XX (x) XX XXX X XX X XXX XX XX XX X XXX XX XXX XXX XXX XX XX XXX XX X XXX XX X XX X XX XXX XXX X XXX XXX XXX XX XX XXX XX XXX XXX XXX XXX XX Fire X X X (x) x(?) X (x) X X X X X X X X X X X XX (?) X X X X XX X X X XXX X X X X x(?) X (?) X X XXX (x) XXX X X X X X X X X XX X X X XX XX Negligible. Mostly advance rot. Advance rot. Much advance rot. Advance rot; negli- gible. Very long scar. Little advance rot. Advance rot. Much advance rot. Sporophore. Two very bad burns held open by frost crack for 85 years; sporophore. Much advance rot; young sporophore. Very bad open fire scar. Much advance rot; 2 sporophores. Mostly advance rot. Advance rot. Slight advance rot. Much advance rot. Sporophore. Sporophore. Much advance rot. Sporophore. Slight advance rot. Tree almost killed at age of 81 years; mostly advance rot. Much advance rot near wounds. Advance rot. Much advance rot in scars. Small sporophore. Rot following scars. Much advance rot; small trfifl. Fire, open Fire (?), with lightning. Frost crack . X XX XX X X Lightning Fire, open Fire Frost crack Fire; lightning . . Fire, open XX XXX XXX XX XX XXX Frost crack Fire, with frost crack. Lightning Fire open Frost crack Frost crack Fire, open XXX X Twin(?) X X XX XXX Knots Fire, with frost crack. Frost f*rack Knots XXX Lightning and knots. Fire XXX XXX Lightning X XXX do Fire open XXX X XXX XX . do ... .. do Frost crack; wounds from falling tree. Fire X XX XX Lightning and frost. Frost crack XX Fire, open Frost crack Fire, open do XXX XX XX XX (?) FOREST PATHOLOGY IN FOREST REGULATION. 45 TABLE II. — 'Condensed data on the pathology of the white fir Continued. No. of tree. Age. Degree of dominance or of suppression. Decay rating. Wound rating. Infection traced to— Appar- ent condi- tion of crown. Remarks. Domi- nance. Inter- medi- ate. Suppres- sion. 1 2 3 4 5 6 7 8 9 10 85 9 13 31 117 83 91 27 12 93 118 160 116 47 81 84 3 51 24 32 29 82 8 57 67 64-a 64-b 36 52 77 71 34 95 107 66 39 86 14 142 73 59 141 152 152 155 155 155 156 156 159 160 160 161 161 162 163 163 164 165 165 166 166 168 169 170 170 170 175 175 178 178 180 183 185 185 186 189 191 192 200 200 221 232 238 XX x XXX XXX XXX XXX (?) XX XX XXX XXX XX XXX X X (?) X X XX XXX XXX X XXX XXX XXX XXX X (?) XXX X X XXX XXX X XX XX X XX XXX XXX XX XX XXX XXX XX X XX X XX X X XX XXX XXX XX XXX XXX XXX XXX X XXX X X XXX XX XXX XX (?) (x) XXX XX XX XXX XXX X X XXX XXX XXX XX XX XXX XXX X XXX XX X XXX Frost crack... do Fire, open X X X X XXX X XX X X X XXX XXX X X XXX X X X X X (x) x(?) XX X X X X X X XX X X X X X X XXX XXX XX (?) XXX Two sporophores. Scar long healed over. Slight advance rot. Much advance rot and shake. Sporophore. Small sporophore. Notes incomplete; D. B. H. 26.5 inches. Much advance rot. Notes incomplete. Very thrifty. Five sporophores. Small sporophores. Advance rot; smaJl tree. Advance rot. Advance rot and shake. Advance rot. Fire 110 years ago. Large sporophore. Much advance rot; small tree. Four sporophores. Much advance rot. Mostly advance rot with shake. Fire... .::::':' Lightning Frost crack Fire open Fire XXX XXX Fire, open Frost crack XXX Fire, open XXX XX XX XX X Knots.. . . Fire do (?) Knot X XX XXX XXX XXX XX Fire Frost crack Knot Fire, open Lightning Lightning X X XX Fire Lightning Fire open Fire XX XXX XXX XXX XXX XXX Frost crack ....do Fire Frost crack with lightning. Lightning Fire with frost crack. Another column concerns the apparent condition of the tree (Table II, column 9) and indicates the appearance of health of the crown, taking the healthy, thrifty tree as normal (indicated by one cross) and marking the degree of deviation from the normal in the usual way. Thus, one cross in parentheses, (x), means that the tree is an exceptionally healthy one ; two crosses (not in parentheses) indicate that the crown is rather poor, either in development or that the color is abnormal, etc.; and a tree having a very much underdeveloped and sickly looking crown is marked with three crosses. The personal 46 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. factor may, of course, lead to misinterpretations unless the same standard is applied throughout the entire study. For this very reason it seemed doubtful from the beginning whether these data would be of much value. They are given here merely for the sake of completeness. The condensed material was again tabulated. In the condensed table (Table II) the relation of decay to age can easily be followed by comparing columns 2 and 6. "Decay rating" is placed between "Suppression" and "Wound rating" in order to bring out forcibly any possible relation between these factors. INTERPRETATION. The column that interests us most is apparently the sixth, "Decay rating." In glancing over this column and comparing it with the neighboring ones we can read directly the connection of decay with factors that may be of influence. Each separate case of decay, of which one, two, or even more can occur on the same tree, may be called, for simplicity's sake, in this study, a "cull case." Each cull case is the result of a separate infection. The actual loss of timber by fire burning out the stump does not concern us here; cull from this source is included in the "volume of rot" whenever the decay is directly traceable to the fire wound. Otherwise the cull from fire is neglected. Cull from knots, limbs, or wind-shake is not considered. Altogether there are 97 cull cases. The first two cull cases are negligible for practical purposes. Some loss occurs in tree No. 125, 84 years old. We see that this is a very badly suppressed tree, very seriously wounded, in very bad health, and that it is injured by both fire and lightning. Another case occurs in tree No. 124, age 87 years. Again suppression, wounding, and condition of health are marked with three crosses, indicating the worst possible conditions, together with two causes of wounds — fire and lightning. In both cases fire is the more serious, lightning often occurring higher up on the tree in numerous small wounds. It carries advance decay to the upper part of the bole and materially increases the volume-rot figure and the decay rating. The next cull case is a slight one (tree No. 88, age 90 years). The tree is inter- mediate, wound rating medium, health good, the decay only advance rot. Continuing down the "Decay-rating" column and comparing the symbols with those in the neighboring columns, we find that in almost every case the rating of rot more or less expresses or is ex- plained by the factors of suppression and wound rating. Apparent discrepancies generally find their explanation under "Remarks" (column 10). Suppression shows at an early age. A distinct preponderance of suppression is noticeable from about the age of 84 years. The first FOREST PATHOLOGY IN FOREST REGULATION. 47 very pronounced cases appear in the same year. They seem to be- come particularly common from about 110 to 120 years. Suppression stands out strongly as an important factor. Out of the total of 97 cull cases, 66 are connected with suppression. Consider- ing that our average volumes over ages were curved from figures which were rather low and that the intermediate white firs in a virgin uneven-aged mixed stand are rather to be considered as recovering suppressed trees than as dominants decreasing in rate of height growth the intermediate class may consistently be added to the suppressed, giving 73 in all, or about 75 per cent. Suppression is commonly con- nected with a more or less high decay rating, provided the tree is wounded seriously. Again, low-volume trees with marked decay are more liable to be a total loss on account of their form. A rot volume percentage of 50, for instance, leaves still a good deal of merchantable stuff in a tree with high volume, but it would make a small tree com- pletely unmerchantable. In the comparatively few cases where dominant trees show decay, the wounding is either of very momentous character or the decay is more or less insignificant and localized near the scars. This is true at least for the younger trees. In glancing over the decay column we see that the higher ratings, xx and xxx, begin rather suddenly to become more frequent after the trees have reached the age of about 123 to 126 years; after the age of about 129 or 130 years they become very common. While decay in the broadest sense of the word may show in trees 60 years old and perhaps younger, the critical age of white fir with regard to more serious decay appears to lie at about 130 years, at least for the region investigated, taking into account that we have to deal here with a practically virgin stand grown up under the cumulative risk from suppression, frost, lightning, and the other factors of influence. Decay of any consequence appears at this age in trees with a combina- tion of wounding and suppression. In the few apparent exceptions the decay is localized near unusually large wounds. We find, further, that up to about 150 (148) years in badly wounded but dominant thrifty trees the decay is either not very far advanced in degree, if in extent, -or that the wounding is of quite extraordinarily severe character. Tree No. 49, age 132, seems to form an exception, but we will see later that frost cracks, though not offering a large opening by virtue of their length, are instrumental in the longitudinal advance of the decay. It seems that after about 150 years thriftiness as expressed by dominance is less able to outbalance the influence of serious wounding. If it is at all permissible to draw any inference from the compara- tively small amount of material at hand, we may distinguish three critical stages in the life history of wounded white-fir trees, and we 48 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. must remember that by far the greater number of our trees, especially after they have reached the age of about 80 to 90 years, are wounded. The first is the "age of infection/' which may be at 60 years or below. Here the infection rarely leads to more than negligible decay unless the tree is handicapped by quite unusually severe conditions, such as very large old wounds. The second, at about 130 years, which we may term the " critical age/7 marks the point after which a combination of pronounced sup- pression and heavy wounding generally results in distinct decay. This combination of deleterious* factors is one commonly found in virgin forests. Wounding alone is not sufficient to unfavorably counteract thriftiness of growth. Another change comes about at 150 years, when even dominant (that is, thrifty) trees become subject to extensive and intensive decay. We might term this the " age of decline/' because the inability of the individual to throw off or keep in check the growth of the wound parasite in its heartwood indicates a distinct decrease in resistive powers, whatever their specific action may be, induced by age. For thrifty but wounded white fir, such as we may expect to raise under management, the age of decline is, therefore, the factor which will influence the rotation and cutting cycles of the species, since for many years to come the risk of inoculation will be more or less the same. There will be fires as long as there are lightning storms. Wounding through lightning and frost are inevitable. Besides, many trees are already wounded. It is of interest to note that of a total of 160 trees only about 25 per cent did not show any wounds except very slight lightning scars. All the rest were wounded from some cause or other. Often a combina- tion of fire, lightning, and frost cracks results in scarring a tree to such an extent that almost in every foot some blemish will be found. This is particularly true of the older trees which have been exposed to the cumulative risk of many years. Any of these wounds, if large enough, may offer an entrance to fungi. After the trees have reached the age of about 80 to 90 years, more than 70 per cent of them are already more or less badly wounded and therefore exposed to inoculation. After they are about 106 years of age more than 80 per cent are wounded. In the remote future, when all these wounded trees are removed and when the risk of wounding for the trees growing up meantime is minimized, a new age of decline may be established. What this age of decline might be for unwounded white fir in managed forests we can not tell from our material, because of 97 cases of decay only 6 were not to be traced to some wounding. It is obviously out of the question to take even a clue from data of so scanty a nature. It may simply be mentioned that the first case of this kind appears at FOREST PATHOLOGY IN FOREST REGULATION. 49 an age of 134 years in a suppressed tree. After all, it may be more than a coincidence that the first case of such infection in a sup- pressed tree occurs near the critical age for suppressed white firs in this region. It is within reason to assume that thrifty, uninjured white firs run only the evidently not very great risk of becoming infected through branch stubs. But decay entering through knots is always caused by fungi of a very aggressive character, such as EcTiinodontium tinctoriunij which is not always the case with wounds. As a possible cause of inf ection we may also mention dead and broken- off leaders or volunteers, the stubs of which are only slowly overgrown. It would appear that, if infections of unwounded trees are really so rare, white fir will take care of itself on the managed areas of the future. This would probably be the case in an ideal, 100 per cent normal forest. But this is Utopian. There will always be a certain risk of wounding. Even after the already wounded individuals are eliminated, which will consume a number of decades, it is unreason- able to expect that our forests should then be so much closer to the normal than the best kept European forests are at the present day. How severe the loss from Trametes pini is in the Prussian forests has already been shown. Whatever may be the final verdict as to the age of decline of unwounded thrifty trees in managed forests, it can not be of more than purely theoretical interest to us and the next folio whig generations. We must cope with present-day conditions as we find them, not as we would wish to have them. The immense importance of fire in connection with decay appears so plainly from Table II that it is hardly necessary to emphasize the fact. The field notes show that in 59 trees wounded by fire, in only 11 was no decay traced to the fire wound. Fire, then, is one of the most important factors in connection with decay; all the more so, as fire generally attacks the butt part of the tree, and decay starting from fire wounds therefore destroys a much greater part of valuable timber than decay in the upper part of the bole. Lightning generally results in comparatively light advance rot. From Table II it appears that the only tree in which serious decay could be traced to lightning, and in which it was neither connected with suppression nor with a serious wound from another source, is No. 59, 232 years old. To judge from our data, lightning is rarely connected with typical decay, although it often renders large parts of the tree partly unmerchantable. The cumulative risk of wounding is shown in Table II (column 7) by the fact that the cases rated with three crosses become far more frequent after the trees have reached the age of about 90 to 100 years. After they have reached about that age such cases are commonly accompanied by decay. Serious decay follows serious wounding after 98035°--Bull. 275—] 50 BULLETIN 215, U. S. DEPARTMENT OF AGRICULTURE. about the age of 130 years (critical age) when combined with pro- nounced suppression, and without this it follows after the age of about 150 years is reached. The risk of wounding increases naturally with the age of the tree. A number of wounded and badly suppressed trees escape infection, although they are far beyond the critical age. Not every wound must necessarily be inoculated. All such cases found are compiled in Table III. TABLE III. — Data on suppressed and wounded but not infected white-fir trees. Age. Suppres- sion rating. Wound rating. Character of wound. Age. Suppres- sion rating. Wound rating. Character of wound. 87 XXX x Fire. 140 . XX x Lightning 110 XXX XX Do 161 XXX Do 111 XXX x Do. 162 XXX x Do. 121 XXX x Lightning 186 XXX XX Do 133 XXX XX Do. 189 XXX XX Do. In all cases but one in Table III the degree of suppression is very high; in this case the wound rating is low. The dangerous fire wounds in this table are confined to the youngest ages, 87 to 111 years; they were comparatively small in each case. The rest of the wounds are all due to lightning, which, as will be remembered, does not open up the interior of the tree unless very large parts of the bark are killed. For inoculation and infection, the character of the wound is all important. Suppression has nothing to do with inocu- lation; only after infection has taken place does its influence make itself felt. The characteristics of each of the three ages, of course, hold good through the following ages. The combination of wounding with suppression, as shown in the critical age, for instance, must continue to favor decay in the age of decline. Relative thriftiness (apparent condition of the tree) seems to have the least influence on the decay factor. It is really nothing but a statement of the present temporary appearance of the individual tree, which may be entirely different from what it was a few years ago or what it will be in the near future. That far-reaching decay must not necessarily be reflected in the appearance and increment of the tree is shown, for instance, by trees Nos. 25 (age 150), 157 (age 150), 85 (age 152), 83 (age 156), and others in Table II. In all the trees mentioned, EcJiinodontium tinctorium had established itself and was vigorously growing. Tree No. 85 (age 152) even had two sporophores, and more than half the volume of the tree was decayed, indicating that the fungus must have lived in the tree for many years. The tree was apparently very thrifty; its volume, 192.5 cubic feet, as against 101, the average for its FOREST PATHOLOGY IN FOREST REGULATION. 51 age (152 years). The increment was good. We can not, therefore, make EcJiinodontium tinctorium responsible for the decrease in thriftiness of infected white fir. In order to further fix the relation between the character of the opening through which the fungus gains entrance into the wood and the character and extent of the decay, all cull cases were tabulated separately (Table IV). TABLE IV. — Cull cases of white fir, showing the extent of typical rot and its relation to the wound through which the infection tooK place. No. Age. Infection traced to — Wounds. Typical rot. Remarks. Open. In- ternal (healed over). Confined to neigh- borhood of wounds. Extend- ing much beyond wounds. 1 2 3 4 5 6 7 8 136 143 125 144 124 88 122 76a 76b 120 132 72a 72b 158 126 102 121 68 80 44 100 78 104 94 99 37 96 97 109 74a 74b 58 69 154 38 56 113 41 60 79 54 63 65 49 42 53 28 55 26 48 50 6 70 119 60 73 84 86 87 90 96 96 96 102 103 104 104 104 105 106 106 107 107 107 110 110 111 112 112 112 113 116 116 119 119 123 123 123 124 124 124 125 126 129 130 130 131 132 133 134 135 135 136 136 137 140 140 140 Lightning X X X X X X X X X X X X X X X X X X X X X X X X X X (?) X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X (?) X X X X X X X X X X X X X X X X E Negligible. Negligible. Advance rot. Advance rot. Remained open 22 years. Almost completely girdled 82 years ago; open 31 years. Negligible. Frost. Frost. Advance rot. Frost. Do. Frost. Do. Knots. Frost. Do. Knots(?). Much advance rot. Sporophore. Fire Fire with lightning Frost crack Lightning with fire Fire — do (x) do Lightning Fire 00 X X X X X X X X X X X do Lightning do Girdling Fire do Lightning Wound from falling tree. Lightning Frost crack Fire ... do . X X X X X X X X X X X (?) X X (?) X do Twin and frost crack. . . Lightning Frost crack Fire... do do Fire(?) . . Lightning Frost crack Lightning Fire .. do Frost crack Fire with lightning Fire . ... Frostcrack Fire with frost crack. . . Lightning Fire Frostcrack do Fire Twin(?) Knots Fire with frost crack Frost crack Knots Lightning and knots — Fire Lightning do 52 BULLETIN 275., U. S. DEPARTMENT OF AGRICULTURE. TABLE IV. — Cull cases of white fir, showing the extent of typical rot and its relation to the wound through which the infection took place — Continued. No. Age. Infection traced to— Wounds. Typical rot. Remarks. Open. In- ternal (healed over). Confined to neigh- borhood of wounds. Extend- ing much beyond wounds. 1 2 3 4 5 6 7 8 155 43 156 61a 61b 4 106 5 92 25 114 157 151 85 9 13 31 117 83 91 12 93 160 81 84 3 51 24 82 8 57 67 64a 64b 52 77 71 95 39 86 14 142 73a 73b 59 141 140 140 141 143 143 146 146 148 149 150 150 150 151 152 152 155 155 155 156 156 160 160 161 163 164 165 165 166 169 170 170 170 175 175 178 180 183 185 191 192 200 200 221 221 232 258 Fire X X X (?) X X X X X X X X X X X X X S (?) X X X X X X X • X X (?) X X X X X X X (?) (7) X X X X X X X X X X X (?) X X X X X X X X (?) X X X X X X X X X Condition very poor; sup- pression XXX. Frost. Advance rot. Notes incomplete. Advance rot. Frost. Frost. Butt open from fire 73 years ago; suppression xxx. Frost. Frost. Suppression xxx. Frost. Condition very poor; sup- pression X. Knots. Notes incomplete. Knot. Frost. Knot. Suppression xxx. Advance rot. Suppression xx. Dominance xxx; fire 110 years ago; deep burn. Frost. Condition very poor; sup- pression xxx. Frost. Advance rot. do do Frost crack Falling tree Fire (?) X X X X X X X X X X X X X (?) X X X X X X X X X X X Lightning and frost Frost crack Fire Frost crack Fire do (?) Frost crack do Fire do Lightning Frost crack Fire do .do Frostcrack Fire Knots Fire do (?) Knot Fire Frostcrack Knot Fire Lightning .. ..do Fire Lightning Fire do Frost crack do Fire Frost crack Lightning do Fire with frost crack. . . . Table IV is designed to show whether and in which cases typical rot extends much beyond the wounds forming the entrance for the fungus. Column 7 is the one to be followed (" Typical rot, extending much beyond wounds")- The affirmative is expressed by a cross, x; the negative by a dash, — . Cases which are on the line between the two are marked by a cross in parentheses; they are negligible for our purposes. The first tree to be considered, No. 58, is 123 years old and has a frost crack. From this age, or rather after 126 to 130 FOREST PATHOLOGY IN FOREST REGULATION. 53 years, these cases become more and more frequent. In most cases, to judge from this table, frost cracks are a strong factor for extending typical decay much beyond the point of entrance of the fungus. By splitting the bole for a considerable length they allow air to enter the wood, which evidently stimulates the growth of the fungus. In noting the cases of decay traced to the wounds or openings through which the fungus found its entrance, it is seen that two and even more cases of decay (cull cases) may be found on the same tree, but each case is counted separately. Where decay is traced to a com- bination of two factors, each factor is shown separately. The means of entrance of the fungus causing decay are thus shown to be as fol- lows: Fire, 48; frost, 25; lightning, 23; other causes (including knots, girdling, etc.), 13; total, 109. These 109 wounds (including knots, etc.) led to 97 cull cases. Out of 109, only 13 were other than wounds from fire, frost, and lightning, and 11 of the 109 cases of decay were the effect of a combination of two of the causes named. Fire has by far the greater share; frost and lightning are second, but the preponderance of fire and frost over lightning is greater than would appear, since they are far more serious with respect to causing decay. If ratings are given, more or less arbitrarily, but yet in keeping with our field observations, to the var- ious causes of wounds in the order of their importance with relation to damaging decay in white fir, taking injury from lightning (the least consequential) as the unit, we have: Fire, 3; frost, 4; lightning, 1; other causes (including knots, girdling, etc.), 3. Then, multiply- ing the figures for means of entrance by these relative ratings we have: Fire, 144; frost, 100; lightning, 23; other causes, 39. These figures express the following facts: (1) Fire injury is not only numerically the strongest, but also commonly leads to considerable cull; (2) frost dam- age is less frequent (above all, less ubiquitous) than fire damage, because it appears only in typical frost belts or frost holes, but it car- ries decay over a much greater length of the bole; (3) lightning injury is fairly common, is also restricted to certain belts, and leads more often to superficial rot; (4) other factors are of importance as causes of damaging decay, but they are comparatively rare. CONCLUSIONS AND OUTLOOK. The interpretation of the results of this study of the white fir from a practical point of view can not leave out of consideration the fact that the basis for all computations and tables is a comparatively small one and that the actual figures and many of the principles derived therefrom have more the value of strong indications for local appli- cation than the force of general laws. Still quite a number of the con- siderations will be directly applicable, at least hi all similar types, some throughout the range of white fir. The writer would emphasize again that the aim of the present study is not to lay down laws, but 54 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. to show by means of one example the problems before us and the various steps leading up to a working method for the future estab- lishment of laws which may — or may not — confirm the conclusions from this study, and to strongly advocate similar studies on a larger scale. With this point plainly in view, but assuming that our con- clusions are a step in the right direction, we may discuss their bear- ing on the silvicultural problems that are before us. DECAY IN RELATION TO WOUNDS. In most cases, decay in white«fir is caused by Echinodontium tinc- torium. The mycelium never enters through the intact bark. Fire wounds offer the most common way of entrance; hence, in the major- ity of cases, decay starts in the butt; frost is less common than fire, but favors the vertical spreading of typical decay. Localized and superficial advance rot, frequently leaving enough merchantable timber in the log to make it worth while handling except when occurring in the upper part of the bole, is often connected with light- ning. Other means of entrance, such as knots, wounds from falling trees, and girdling by rodents are comparatively rare. These factors group themselves naturally into such as are uncon- trollable and such as may be controlled directly or indirectly. The en- trance of decay through knots, wounds from trees and limbs thrown in heavy storms, or from excessive snowfall lies beyond our control. Injury from mammals as a starting point of decay is very rare and will become even more so with the decrease of the forest fauna. The other factors are more or less open to influence. Fire is dis- tinctly a directly controllable factor. Lightning and frost are, of course, not directly controllable. It is a fact, however, that both do not occur to any damaging extent except in more or less well-defined belts, and generally more heavily in foci inside of these belts. The natural inference would be not to favor white fir in such belts when possible. As a first step in this direction the establishment and map- ping of frost belts, frost holes, lightning zones, and lightning foci would be of particular value, which should not be confined to white fir alone. Other forest trees are also more or less subject to injury from both factors. The value of such maps should also make itself felt in forest-fire control, for the proper distribution of protective forces and improvements. FOREST REGULATION. CARE OF VIRGIN FORESTS. It has been heretofore pointed out that practically the only means of silviculturally influencing the national forests on a larger scale at the disposal of the administration at the present time lies in the han- dling of timber-sales areas. On all the vast forests outside of these FOREST PATHOLOGY IN FOREST REGULATION. 55 comparatively restricted areas the same beneficial and injurious con- ditions must continue to prevail, which on one hand govern the annual increment and on the other make for annual total loss. Only one single component of the total-loss factor, though a most important one, may be controlled to a certain degree directly. Forest fires are in ever-increasing ratio eliminated from the national forests and, therewith, also the danger of trees being fire scarred and opened to the attacks of heartwood-destroying fungi. But the best of fire pro- tection can not restore to their original state of intactness the over- whelmingly large number of older trees which have been opened by previous fires. The open fire wounds continue to offer an easy entrance to fungi. It is true that fire protection prevents small wounds from becoming larger and keeps healing wounds from being opened again by repeated fires. The sooner such fire-wounded trees, as well as all other undesirable individuals, including all badly injured, diseased, and misshapen ones, can be eliminated from the forest, the better. There is little hope, however, for this to be done outside of timber sales. Adequate fire protection, both of water- sheds and of commercial timber, must of necessity be paramount to* silvicultural work of this kind. Practically virgin forests may also be influenced by sowing and planting. This is done on so small a scale, compared to the total of existing forests, that we can hardly speak of any real silvicultural change. Knowing, however, that white fir can not be expected to yield full returns in belts subject to lightning and severe frosts, the forester should avoid favoring white fir in such localities. FOREST REGULATION THROUGH TIMBER SALES. Cutting timber does not in itself constitute sound silviculture. It may lead to regulation, or it may spell ruin to the forest. The administration of the national forests is not able to have timber cut by selling it where cutting is most needed. Accessibility, local demand, and last, not least, the quality and condition of the timber are stronger factors in finally locating a timber-sales area than silvicultural needs. A strong admixture of inferior species in itself is often sufficient to let an otherwise attractive sale fall through. Here, the prejudice of the purchaser against such species as white fir and incense cedar is responsible for forcing the Forest Service to leave an area badly in need of improvement in its virgin state, with all the cumulative risk to which it is exposed. The prejudice against white fir is widely established and not always confined to the lumberman. From a silvical point of view the prejudice is directed against its very aggressiveness, which tends to give the species an ascendency over the more valuable but less tolerant pines. But the disfavor in which it is held by the forester is really nothing but a reflection of 56 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. the strong objection made by the purchasing lumberman to accepting white fir in Government timber sales, and this is based mainly upon the unsoundness of the timber. At the same time, there is a fair local demand for sound white fir for a number of uses. There is no valid objection to clear and sound white fir. In fact, many a purchaser would rather pay higher stumpage for white fir if he were allowed to take only sound young stuff, which is in demand for dimension stuff (2 by 4, 4 by 4, etc.), for frame stuff, timbers, and stickers, and for butter boxes, etc. Purchasers complain that much of the material, though seemingly sound, "has np life" after going through the mill; it becomes brittle and falls to pieces when dry. Sound white fir neither becomes brittle nor does it fall to pieces. It is the unsound material (advance rot) only which is objectionable. The remedy is easily seen; it consists in liberal and judicious scaling, which would rather give the purchaser the benefit of the doubt. The sealer will find valuable aid in the occurrence of decayed knots on the boles of trees affected with stringy brown-rot. To the casual observer they may appear normal; when they are knocked off with a hatchet or similar instrument the decayed rusty interior is exposed. These ' 'rusty knots" afford, in the vast majority of cases, a valuable indication of more or less far-gone Echinodontium rot in the heartwood of white fir. Occasionally, the rusty color is missing, but the center of the knot is unmistakably decayed. The verdict as to the rottenness of the heartwood will be the same. The knots are often very small. When sound, they are very brittle and glassy in appearance. To give a practical example: No. 82 on the Otter & Burns tract, a very fine tree with a long clear bole, 29.4 inches diameter breast high, and 154 feet high, had been given a full scale. The bole had been bucked into 16-foot logs. To the sealer there were no indications of decay. After examining the tree the writer threw out log 5. The only indication for spotting Echinodontium decay in this log was the presence of the rusty knot. The log was opened and found to be unmerchantable from 0.5 to 5.6 feet from the lower end, leaving as merchantable 0.5 foot on one end (diameter 19.5 inches) and about 10 feet on the other end (upper diameter 16.3 inches). Had the defect been known to the bucking crew a more advantageous dividing up of the bole in log lengths to the exclusion of the decay would have meant a saving to the operator. Among others, Bryant1 has pointed out the necessity of more judi- cious bucking and of closer utilization. i Bryant, R. C. Waste in cutting timber. In Amer. Forest., v. 19, no. 11, pp. 790-799, 7 figs., 1913. FOREST PATHOLOGY IN FOREST REGULATION. 57 MARKING. The entire silvicultural results obtainable by way of timber sales are directly dependent upon proper marking, the importance of which can not be overemphasized. Marking is by far the most portentous of all silvicultural activities and requires a very specific training, of which a complete knowledge of all components of the total-loss factor must be a prominent part. Marking in the selection forest has a threefold object — to select trees to be cut and utilized at once, to leave others as a basis for future cuttings, and to establish desirable reproduction. Here the interests of the Government as timber owner and timber producer frequently conflict with those of the purchaser. The purchaser can not be expected to take a strong interest in the future of the area he is to cut over. He quite naturally wants as much sound merchant- able timber from a given stand as possible. The larger the amount of timber he can cut from an area the smaller the overhead charges will be per thousand feet, board measure. In offering white fir for sale it is, therefore, important to be able to estimate more or less correctly the amount of sound timber on a given tract. If our figures prove correct, the loss factor in white-fir trees will be com- paratively small up to an age of about 130 years; after trees with a combination of wounding and suppression have reached the age of 130 years they are liable to contain decay; after they have reached the age of 150 years wounding alone, even in dominant trees, is liable to lead to damaging decay. That trees with sporophores are decayed, at least partly, is self-evident. The actual cull per cent from decay is at present only guessed at. It is the constant aim of forest pathology to reduce this guesswork to actual and concrete figures. It is intended to repeat similar studies throughout the range of white fir and later also on other species in the order of their importance and finally to establish broad zones of equal path- ological conditions, in which the rot percentage may be given in definite figures. . Marking can only be done correctly if the outcome of the marking with regard to the trees left standing is constantly kept in mind. In our specific case, for instance, white fir on typical lightning and frost belts should be marked very heavily. We know that here the loss from decay, particularly following frost cracks, is heavy and will grow through cumulative risk. White firs with serious wounds, especially with partly open fire wounds,' must be marked heavily to as low a diameter as practicable. On the other hand, thrifty unwounded trees, where desirable, may be left without much risk up to the age of about 150 years, and prob- ably much longer. 58 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. The effect of logging on the pathological condition of white firs that are left on the area may be twofold. The opening of the crown cover through cutting will prove beneficial to all suppressed and interme- diate white firs. The ready response of the species to light is well known. It is probable that such trees, if already infected, will not allow the decay to proceed very much farther, i. e., the newly formed upper logs may be sound. These trees move up into the dominant class. The mycelium in the heartwood, however, if well established, will not die out, and after a while sporophores appear which carry the disease to hitherto sound trees! As there can not be any infection except through spores coming from sporophores on diseased trees, it is evident that it is poor silviculture to leave individuals infected with any parasite of economic importance on cut-over areas. Such trees on timber-sale areas should be marked and cut under all circum- stances if we expect to save and utilize the sound timber they may contain and to protect other trees from decay. Sanitation of the forest must be the first and fundamental step in forest regulation. The introduction of the so-called sanitation clause in the timber-sale con- tracts of the Forest Service aims at this very point. It is evident that blind enforcement of the sanitation clause, following the letter and not the spirit of the principle expressed, is just as pernicious as laxity in its application. Not all parasites are of equal importance; our efforts should first be concentrated on the most dangerous ones. The time will come when forest sanitation will include all controllable elements making for loss in timber volume and timber values. On the other hand, if only thrifty trees are left standing after log- ging operations, they are, by the very opening of the " forest screen/7 more exposed to flying spores from surrounding untreated tracts, but unless wounded they are in no great danger of infection. The smaller the tract, the more will this influence make itself felt. The improved conditions under which they grow will help them to either overcome or limit the extent of decay in case they do become infected. As long as we do not possess any exact figures on the recovery of white fir on cut-over areas, however, it is advisable to consider wounded white-fir trees left standing as unaffected by the opening up of the stand, at least during the transition period, that is, in first fellings. All these trees have grown up under unfavorable conditions, and the chances that they are lastingly injured are considerable. By the time second logging operations cover the area, it is to be assumed that a more pro- found knowledge of the life history of white fir will be at hand. The choice of white-fir trees to be left on the area, with the expecta- tion that they will be sound and merchantable at the next felling, depends altogether on their condition and the length of time probably elapsing until that felling takes place. Assuming that our figures FOREST PATHOLOGY IN FOREST REGULATION. 59 are correct and that the next cutting may occur, for example, in 30 years, we may with comparatively small risk leave thrifty unwounded trees of any age on the area; wounded but thrifty trees of more than 120 years are to be cut, wherever practicable, because in 30 years they will be over 150 years old, at which age trees of this class are more liable to deteriorate. Wounded trees which at the same time are suppressed should be eliminated. It is bad silviculture to leave individuals in the forest which not only do not produce the maximum of timber but which in all probability will prove a total loss and which occupy the place that should be fully stocked with trees promising a full and sound crop. In case of an emergency, such as occurs under very unfavorable market conditions or where the protection of young stuff is the most important feature, wounded and sup- pressed white firs left standing should not be older than 100 years, since in 30 years they will have reached their critical age — that is, 130 years. After they have reached this age it appears that dam- aging decay becomes prevalent in trees of this description. Very severely injured trees have, of course, no place in the managed forest. The same is true for unusually suppressed or unhealthy trees, unless it may be expected with reasonable certainty that the opening of the crown cover will benefit them materially. Trees with open fire scars and with open frost cracks should be cut in preference to those with lightning scars or those having wounds from falling neighbors. In short, all wounds reaching far into the wood are to be given a higher rating with respect to decay than superficial wounds unless the latter are unusually large. PATHOLOGICAL ROTATION AND CUTTING CYCLES. Since we may expect that cutting during the period of transition will practically eliminate all those trees which by their combination of suppression and wounding become subject to early decay (critical age), the age of decline forms the basis for what might be termed the "pathological rotation," for want of a better expression. It does not indicate that a given species should most advantageously be cut in regular intervals expressed by the pathological-rotation age, but that it should not be cut at a higher age. It is really a factor limiting the rotation and therefore also the cutting cycle. Rotation based on maximum volume alone can not be more than a makeshift during the transition period; logically it should be nar- rowed down to maximum-volume production of sound timber. Such species as Sequoia gigantea and Sequoia sempervirens are so resistant to decay that their pathology will not influence then- rotation at all. In some of our valuable pines the pathological rotation will probably be very high, either coinciding with or reaching beyond the age of maximum-volume production. In white fir, incense cedar, and a 60 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. number of other so-called inferior species, the pathological-rotation age is presumably lower than the age of maximum-volume pro- duction. We must look to forest mensuration for final data to settle this point. Barrington Moore * advocates a rotation based on the " period dur- ing which the rate of volume production is greatest or shortly after it, provided it is long enough to give the most valuable product."2 Here, again, the pathological rotation will be the limiting factor, except for species in which the rate of greatest volume production possibly occurs at a lower age than the pathological rotation. That the value of lumber grades is bound to play a far more important r61e in the future than at present, with regard to rotation, is a fore- gone conclusion. So far, we have considered only the rotation per species. In pure or almost pure stands the rotation of the unit is determined by the rotation of the species clearly dominating, not only numerically, but also in value. As soon as two or more equally valuable commercial species appear together in about the same proportion, the rotation of the stand becomes " synthetic;" that is, the rotation for the unit is governed by the individual rotations per species. In the great majority of cases neither the representation of the species nor their individual values are the same. Nearly always there will be certain species more desirable than others, which latter then are classed as more or less inferior. A weak representation of inferior species with low pathological rotation will be without much effect upon the synthetic rotation of the unit. The stronger the representation of inferior species, the heavier will be their bearing on the synthetic rotation. On many of the large private holdings of the West the inferior species are disregarded altogether; they are simply left standing in logging operations. Unless the logged-over area is burned, the representation of inferior species is then an unduly heavy one. They must necessarily dominate the stand in the future. The national forests, on the other hand, will be the regulated for- ests of the future. In many of the national forests, particularly in the West, several species of unequal value are represented on the same unit in such a manner as to make each one a strong factor to be considered. Here, regulation of yield must be based upon synthetic rotation and synthetic cutting cycles. Rotation and cutting cycles for each species must be determined separately, each on the chosen basis of either maximum-volume production, or rate of maximum- volume production, or production of maximum value, limited in 1 Moore, Barrington. Chapman's method of studying yield, p. 94, 1913. To accompany forest plan, Plumas National Forest, district 5. Appendix (continued), Silviculture. (Unpublished. Furnished by courtesy of the U. S. Forest Service.) 2 See also Zon, Raphael, Balsam fir, U. S. Dept. Agr., Bui. 55, 68 pp., 2 pis., 8 figs., 1914. (See p. 67.) FOREST PATHOLOGY IN FOREST REGULATION. every case by the age of decline. The synthetic rotation is figured on the basis of the specific rotations, under due consideration of rep- resentation and relative value of each species from a commercial and silvical point of view. The same is true for cutting cycles. It should not prove impossible to express both representation and relative value for each species in symbols, which, together with the specific rotation, would permit the balancing of each species against the others, and thus to arrive at the synthetic rotation of the entire unit. In this way the inferior species will be given their proper place in for- est regulation. This procedure is undoubtedly followed more or less consciously wherever regulation is planned by way of timber sales. It can not be reduced to a practical working system, however, until all factors upon which it is based are thoroughly known. The pathological rotation limits the rotation of white fir, on the basis of our present knowledge, to 150 years — at least during the transition period. Perhaps the actual felling age for the species will be shortened long before that time arrives. The chances of pro- viding for the next decades are distinctly better. On areas cut over to-day we may expect second operations in not too remote a future, taking the place of a second improvement felling. Provided our figures prove correct, the critical age and the age of decline will be a safe guide in tentatively fixing cutting cycles for white fir, which, together with the cutting cycles for the other species present, will permit the establishment of the synthetic cutting cycle for the unit. Our present knowledge of the pathology of white fir leads us to the following practical conclusions for the period of transition: Prejudice against white fir as an inferior species. Conservative scaling (excluding advance rot) in favor of the purchaser on the one hand and of better utilization of sound white fir (where market conditions permit) on the other will in time overcome the prejudice . Silvicultural treatment of white fir. Reproduction: Frost and lightning zones are to be avoided. Marking on timber sales: On frost and lightning zones marking should be heavy. Badly wounded trees, particularly those with open fire scars or frost cracks, should be marked heavily. Badly suppressed trees should be marked heavily. Trees with a combination of wounds and suppression can not be figured on to remain fairly sound beyond the critical age of about 130 years. The age of such trees, if left standing, added to the number of years to elapse before the presumable next cutting takes place, must not exceed 130 years. Trees wounded, though thrifty, can not be counted on to remain sound beyond the age of decline of about 150 years. The age of such trees, if left standing, added to the number of years to elapse before the presumable next cutting takes place, must not exceed 350 years. Rotation, and cutting cycles. The rotation for white fir, as far as we can judge now, can not exceed 150 years. Cutting cycles for white fir must be limited by the age of decline. 62 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. OUTLOOK. The weak point in the example (white fir) discussed in this paper lies in the fact that the numerical basis of trees examined is insuffi- cient. Besides, what may be true for one set of conditions may prove wrong in another. Extensive additional studies on white fir in different regions of its range have been carried out during 1913. What has been done for white fir must be done for the other species as well. Investigations on incense cedar have yielded suggestive results; others are to follow. But not before all important species, from the lowest to the most valuable, have been studied carefully with regard to their pathology Can we expect to definitely figure the total-loss factor for any unit. To-day we are standing at the very beginnuag. Each species has its specific fungi, either one (as in the case of incense cedar) , or practically one (as hi the case of white fir) , or several (as in the case of Douglas fir, sugar pine, and yellow pine) . The relative importance of each of these fungi, their relation to influencing factors, their prevalence throughout the range of their hosts, and, finally, the establishment of the critical age and age of decline from a pathological point of view, are still to be worked out. To this we must add the study of all the other components of the total-loss factor. The amount of work left to be done is enormous and will require many years. Concentration on the inferior species will yield results in a shorter time, enabling us to establish general rules to guide us in the transition period without causing too much damage to the interests of future generations. PUBLICATIONS OF THE U. S. DEPARTMENT OF AGRICULTURE RELATING TO DISEASES OF TREES. AVAILABLE FOR FREE DISTRIBUTION. Death of Chestnuts and Oaks Due to Armillaria Mellea. (Department Bulletin 89.) Disease of Pines Caused by Cronartium Pyriforme. (Department Bulletin 247.) Larch Mistletoe: Some Economic Considerations of Its Injurious Effects. (Depart- ment Bulletin 317.) Miscellaneous Forest Tree Diseases Common in California and Nevada. (Forestry Miscellaneous.) FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS. The Present Status of the Chestnut Bark Disease. (Bureau of Plant Industry- Bulletin 141, pt. 5.) Price, 5 cents. Diseases of Deciduous Forest Trees. (Bureau of Plant Industry Bulletin 149.) Price, 15 cents. Mistletoe Pest in the Southwest. (Bureau of Plant Industry Bulletin 166.) Price, 10 cents. Timber Rot Caused by Lenzites Sepiaria. (Bureau of Plant Industry Bulletin 214.) Price, 10 cents. Diseases of Ornamental Trees. (Separate 463, from Yearbook 1907.) Price, 5 cents. Chestnut Bark Disease. (Separate 598, from Yearbook 1912.) Price, 5 cents. Practical Tree Surgery. (Separate 622, from Yearbook 1913.) Price, 5 cents. 63 ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 10 CENTS PER COPY UNITED STATES DEPARTMENT OF A BULLETIN No. Contribution from the Bureau of Plant Industry WM. A. TAYLOR, Chief Washington, D. C. PROFESSIONAL PAPER January 15, 1917 ENDOTHIA PARASITICA AND RELATED SPECIES. By C. L. SHEAR, Pathologist, and NEIL E. STEVENS,* Pathologist, Fruit-Disease Investigations, and RUBY J. TILLER, Scientific Assistant, Office of Investiga- tions in Forest Pathology. CONTENTS. Taxonomy Page. 1 Physiol Introduction 1 Dis The genus Endothia 3 Dis The species of Endothia 13 c MorDhology and development 22 Dis 22 Pre Stromata 23 si Spore measurements 30 HOE Physiology 36 Summa Cultural studies 36 Literati Distribution of the species of Endothia. . Discovery of Endothia parasitica in China Discovery of Endothia parasitica in Japan Present distribution of Endothia para- sitica in America Host relations of the species of Endothia . Page. 48 54 58 .39 BO 74 77 TAXONOMY. INTRODUCTION. The discovery of a serious canker of the chestnut in the New York Zoological Park in 1904, by Merkel (49), 2 first attracted the atten- tion of pathologists and foresters to what has proved to be one of the most serious epidemics of a plant disease ever known in this country. The fungus which was found associated with these cankers (PI. I and PL II, fig. 1) and soon demonstrated experimentally to be their cause was described by Murrill (57) in 1906 as a new species, of Diaporthe (D. parasitica). Search for the fungus in other places in New York and vicinity soon showed that it was already estab- lished and apparently rapidly spreading. Investigations which have been continued and extended from year to year have shown 1 Formerly Pathologist, Office of Investigations in Forest Pathology. 2 Serial numbers in parentheses refer to " Literature cited," at the end of the bulletin. NOTE. — This bulletin is of value to botanists, especially plant pathologists and mycolo- gists, and to all persons who are interested in the study of chestnut blight. 43737°— Bull. 380—17 1 2 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. conclusively that the disease is spreading very rapidly, especially west and south from New York and also north and east. The exact identity and relationships of the fungus causing the disease and the origin of the epidemic soon became the subject of study by various mycologists and pathologists. Different explana- tions were offered for the sudden appearance and behavior of the disease, one view being that the fungus was probably a foreign parasite which had been introduced ; another, that the organism was probably a native species which had recently attracted attention, chiefly by reason of the weakened condition of the chestnut trees due to abnormal climatic or other, conditions. In attacking the problem of the origin of the parasite and its pos- sible control, it was evidently necessary to secure all the information possible in regard to its life history, identity, distribution, and re- lationships. The senior writer in an unpublished paper prepared in 1908 pointed out the close relationship and possible identity of Diaporthe parasitica with certain species of Endothia. Clinton (16) and Farlow (28) soon after also made the same suggestion. Two species of Endothia had already been described from this country by Schweinitz (74) under the old generic name, Sphaeria. These, however, had in recent years been regarded as a single species and referred to Endothia gyrosa (Schw.). Owing to a lack of knowledge of the types of these two species and for want of good specimens showing ascospores, it was difficult to determine what species of Endothia were indigenous in the eastern United States. Since it had been suggested that Diaporthe parasitica was either identical with one of Schweinitz's species or a mere variety of it, the present waiters undertook a thorough study of the genus Endothia in its taxo- nomic, ecological, and pathological relations. It was first necessary to determine the identity of the two species already described by Schweinitz from America and also to learn their distribution and host relations. As one or both of Schweinitz's species were reported to occur in southern Europe on chestnut, it was important to obtain exact knowledge in regard to the identity and relationships of the European species. The senior writer spent several months in Eu- rope collecting material of Endothia in the field and studying her- -barium specimens of types and authentic collections of Schweinitz and other authors. Material was also acquired by collection and exchange with pathologists and mycologists in nearly every region of the world in which Endothia was known to occur. Comparative cultural studies were made of all the living material secured, as well as inoculation experiments on various hosts. The recent discovery of the typical chestnut-blight parasite, Endothia parasitica, by Meyer (27, 76, 78), in China and Japan and the failure to find in Europe or America any native form which would produce the disease appear to settle beyond question its foreign origin. ENDOTHIA PARASITICA AND BELATED SPECIES. 3 The present paper presents the results of several years' field and laboratory study of the species of Endothia. This includes the study of practically all the herbarium material of this genus preserved in the principal herbaria of Europe and America; also field and lab- oratory studies of over 600 new collections from various localities and hosts in America, Europe, and Asia. Over 4,000 cultures have been studied and about the same number of inoculations made. These studies include the systematic relations of the species of Endothia and their physiological behavior on various culture media and under various conditions of light, moisture, and temperature; also inoculation experiments with the various species on various hosts. The writers wish to record here their grateful acknowledgment and thanks for opportunities to examine specimens and for assistance rendered by various mycologists and pathologists and directors and curators of botanical gardens and museums, especially the following : Prof. O. Comes, Naples; Prof. Eomualdo Pirotta, Prof. Giuseppi Cuboni, and Drs. E. Pantanelli and L. Petri, Kome; Prof. P. Bac- carini, Florence ; Prof. P. A. Saccardo, Padua ; Dr. G. Briosi, Pavia ; Dr. J. Briquet, Delessert Herbarium, Geneva; M. G. Beauverd, Boissier Herbarium, Geneva; Prof. L. Jost, Strasburg; Prof. W. Pfeffer, Leipzig; Dr. G. Lindau, Berlin; Dr. J. W. .C. Goethart, Leiden; Prof. H. O. Juel, Upsala; Dr. P. Hariot, Paris; Sir David Prain, Kew ; Dr. A. B. Rendle, British Museum ; Prof. I. B. Balf our, Edinburgh; Prof. T. Petch, Peredeniya, Ceylon; Dr. C. Spegazzini, La Plata, Argentina; Dr. W. G. Farlow, Harvard University; Dr. W. A. Murrill, New York Botanical Garden ; Mr. Stewardson Brown, Philadelphia Academy of Science; Dr. G. T. Moore, St. Louis Botanical Garden; Prof. E. Bethel, Denver, and Drs. G. P. Clinton, P. J. Anderson, and F. D. Heald. The writers have also received specimens and cultures from numerous other colleagues which have been of great assistance and are duly appreciated. THE GENUS ENDOTHIA. The genus Endothia was established by Elias Fries in 1849 (33, pp. 385-386), as follows: (X. Endothia. Fr.*) * Colore rubro fulvove, habitu Tuberculariae, peritheciis cellulosis difformi- bus pallidis, ascis diffluentibus, facile distinction genus, nobis exoticum, sed jam in Europa australi obvium v. c. Sph. gyrosa Schw. — et subgenus, tuber- culo uniloculari, sistit 8. Tiibercularia Dec. Omnium horum generum char- acteres proxime plenius exhibeamus, examinatis multis speciebus exoticis. The description of the genus transcribed here was published as a footnote in the work cited and was evidently based on the specimens contained in Fries's herbarium at the time the book was written. 4 BULLETIN 380,, U. S. DEPARTMENT OF AGRICULTURE. Fries (31, p. 73) had at that time, according to his own statement, authentic specimens of Sphaeria gyros a sent him by Schweinitz and also the specimens collected by Guepin and Levieux in France, which he identified as this species. In Fries's herbarium at Upsala at present are found specimens of true S. gyrosa Schw. with Schweinitz's autograph label, but no specimens of S. gyrosa could be found attributed to Guepin or Levieux. There is a small packet marked " Sph. gyrosa" apparently in Fries's handwriting, but there seems to have been some confusion in the labeling or mounting of this specimen, as a small stroma of Hypoxylon annulatum which does not look at all like Endothia is included. The other piece consists of an irregular pycnidial stroma which may be the southern European specimens referred to in the description quoted. Fries's identification of this European material as E. gyrosa was apparently based chiefly upon its superficial resemblance to the pycnidial stromata of Schweinitz's American specimens. The senior writer has seen and made a careful microscopic examination of a specimen col- lected by Guepin in France and preserved in De Notaris's herbarium at Rome. It is labeled "Sphaeria gyrosa Fries, Guepin, Angers." The specific name " gyrosa " has been crossed out by De Notaris and " radicalis Schw." written above it and the date " April, 1845," added. This appears to be a part of the same collection that Guepin sent to Fries, as the specimen agrees well with Fries's description and consists chiefly of pycnidial stromata which are rather larger than is usual for Sphaeria radicalis and show con- siderable superficial resemblance to the stromata of Sphaeria gyrosa Schw. A thorough examination of this specimen, however, reveals a few perithecia and ascospores, which leave no doubt that it is 8. radicalis of Schweinitz, as indicated by De Notaris on the label. What the plant sent Fries by Levieux was is unknown, as no speci- men so labeled could be found in Fries's herbarium. It appears from all the evidence at hand that Fries was mistaken in his identi- fication of the material from Levieux and Guepin, as no specimens of the true Sphaeria gyrosa Schw. have yet been seen from Europe. There seems to be no doubt, however, that Fries intended the true Sphaeria gyrosa Schw. to represent the type of his genus Endothia, as he had a part of Schweinitz's original collection at the time and never definitely placed any other species in the genus; hence, Sphaeria gyrosa Schw. should be adopted as the nomenclatorial type of the genus. It is clear from Fries's writings and specimens that he knew Sphaeria radicalis Schw., as he had American speci- mens from Schweinitz as Avell as European collections at the time he founded this genus. He did not, however, apparently regard it as congeneric with &. gyrosa. His specimens of $. radicalis show ENDOTHIA PARASITICA AND RELATED SPECIES. 5 the typical perithecia with necks, whereas no perithecia have been found in any of Schweinitz's specimens of /S. gyrosa examined by the writers. Fries, in common with Schweinitz, regarded the pyc- nidial cavities of 8. gyrosa as perithecia. When the pycnidia of 8. gyrosa are mistaken for perithecia and compared with the real perithecia of S. radicalis the differences appear marked. It was therefore quite as natural for Fries to place the two species in different genera as it had been for Schweinitz to place them in dif- ferent tribes of the genus Sphaeria. Fries's mistake in describing as perithecia the pycnidial cavities in the stroma of 8. gyrosa ex- plains his reference to the asci as " ascis diffluentibus." Believing that he had perithecia but finding no asci, he interpreted this as indicating that they had disappeared. According to the plan of accepting only names originally applied to the ascospore stage, this name would be invalid, as proposed by Fries, and would be attributed to De Notaris, who placed the peri- thecial form of Sphaeria radicalis Schw. in the genus and described the ascospores. There is not the slightest question, however, in regard to the identity of the different stages of this fungus and their genetic connection, and the name Endothia has been almost invariably applied to these two species in both stages. SYNONYMY. There are only two true generic synonyms of Endothia: En- dothiella Saccardo, 1906 (71, p. 278) and Calopactis H. and P. Sydow, 1913 (81, p. 82). Endothiella was based on Endothiella gyrosa Sacc., which, according to authentic specimens from Saccardo, is undoubtedly the pycnidial form of Endothia flicens as found in Italy. Calopactis was based on C. singularis, the pycnidial condi- tion of Endothia singularis (H. and P. Syd.) S. and S. Ascospore cultures of this have not yet produced any pycnidia, but the proof of the genetic connection of the two stages appears rather con- clusive from the occurrence of pycnidia and perithecia in the same stroma, as shown in Plate XII. Perithecial stromata and ascospores were also found in the specimen of the Sydow exsiccati in the Patho- logical and Mycological Collections of the Bureau of Plant Industry. Von Hohnel (43, p. 1479-1481) considers Cryphonectria Sacc. as a synonym of Endothia, taking C. gyrosa (B. and Br.) as the type of that genus because it is the first species listed by Saccardo in con- nection with his description of the genus. Saccardo, however, had previously established Cryphonectria as a subgenus, with C. abscon- dita as the type, which is not an Endothia. Valsonectria is also con- sidered by Von Hohnel a synonym of Endothia, but apparently he had not compared specimens of Spegazzini's fungus, which is found upon examination of the type species to be separate from Endothia. The 6 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. Tulasnes (83, p. 87-89) do not appear to have regarded Endothia as distinct from Melogramma, to which they referred E. gyrosa. The type of Melogramma, however, is M. melogramma (Bull.), which has a somewhat similar stroma, but the ascospores are 3-septate and dark colored and the perithecia not separable from the stroma, while the pycnospores are long, slender, and curved. STUDY OF EARLY COLLECTIONS AND TYPES. There has always been more or less uncertainty in regard to the identity of the older species of this genus of fungi. In order to get more light on this subject, a thorough study of all the available ma- terial in the way of literature, type specimens, and' manuscripts was made. The first species to be described in this country was Spkaeria gyrosa Schw. This was collected by Schweinitz at Salem, N. C., and published in 1822 (72, p. 3).1 Two hosts were given in the original description, Fagus and Juglans. As Schweinitz's description was prepared before the advent of careful microscopical studies and spore measurements, it is impossible to identify the organism satisfactorily from the original description. It was, therefore, important, if possible, to locate the type specimens upon which the description was based. Schweinitz's herbarium was left at his death, in 1834, to the Philadelphia Academy of Science. His specimens of fungi at the time they were transferred to the acad- emy were contained in small, folded paper packets, as shown in Plates V and VI. These packets were then inclosed in other heavy paper wrappers, folded to small quarto size, and three or four of these large packets, each bearing a manuscript list of the species contained, were then inclosed in quarto pasteboard covers, tied with tape. The in- dividual species packets were labeled in Schweinitz's handwriting, with the name of the species and the locality of the collection, as shown in Plate V, figure 2. These species packets frequently bore the names of several locali- ties, but usually two, Salem. [N. C.] and Bethlehem [Pa.], as most of his collecting was done at these places. This fact, in addition to the evidence afforded by the specimens in the packets, clearly indicates Schweinitz's method of handling his specimens. Frequently some of the specimens in a packet show the remains of a gummed strip. This will be noticed in Plate III, which indicates * 24. Kphaeria gyrosa Sz. 8. subperipherica minor gregaria subconfluens aurantio miniata, sphaerulis gyrosis farc- tis demum prominulis pulverulentis, stromate lutescenta. In cortice nondum corrupto etiam vivo Fagorum et luglandum. Junior planiuscula, ubi adolevit sistit corpus subrotundum, tuberculis minimis et magoribus asperum et gyrosum. Sphaerulae farctae, teretes, supra gyrosae, paucae, radiatim divergentes a superficie ad centrum fere stromatis continnantur, primum sublantes, demum prominulae, cortice pul- verulento ; ipsum tamen centrum farinacea carne componitur. Gelatina asciphora albet. Ostiola indistincta. — Transitum facit ad Sphaerias septimae divisionis. ENDOTHIA PARASITICA AND RELATED SPECIES. 7 that at one time the specimen was apparently attached to a sheet by a gummed paper strip. This seems to have been the way in which Schweinitz originally mounted his specimens, but later, apparently, he changed to the plan of putting them in paper packets and removed those which had been attached to sheets. It is clear from an examina- tion of the specimens still found in some of the original packets that two or more different hosts were sometimes included. In some cases as many as four or five different collections appear to have been placed in the same packet and each new locality added on the out- side. This method of keeping specimens makes it rather difficult in some cases to determine which belongs to the first collection. In the case of Sphaeria gyrosa but two localities are indicated on the packet, Salem and New England. (See PI. VI, fig. 2.) The difficulties in determining the true type specimen of any species would have been sufficiently great if the collection had been preserved as it was left by Schweinitz. The matter is, however, further complicated by the later handling and rearrangement of the collection. Some time after Schweinitz's death (the exact date the writers have been unable to determine) his collection of fungi was more or less completely rearranged and mounted. The greater part of this work was evidently done by Dr. Ezra Michener. Dr. Mich- ener was a lifelong resident of Chester County, Pa. He early be- came interested in botany, and in 1840 was elected a correspondent of the Philadelphia Academy of Natural Science. He paid special attention to the collection and study of fungi and corresponded and exchanged with various mycologists, especially Curtis and Ravenel. He left a large collection of fungi, which the writers have recently had the privilege of examining. Among his specimens are found many labeled "Ex. Herb. Schw.", which are undoubtedly part of Schweinitz's original collections at the Philadelphia Academy. These specimens, as well as all of Michener 's fungi, are mounted in exactly the same manner as the mounted portion of Schweinitz's col- lection at the Philadelphia Academy. The mounting paper, the specimen slips, the arrangement, manner of attachment, and the handwriting on the labels are identical, as will be readily perceived by comparing the illustrations from photographs of sheets from both herbaria. It is, therefore, clear that the mounted collection of Schweinitz's herbarium was prepared by Dr. Michener. He evi- dently took from Schweinitz's original paper packets what appeared to him to be the best or most typical specimen of the species in the packet and attached it with glue to a square slip of paper, as shown in Plate III. Where there was but little material in the original packet it was all mounted in this manner. In case there were several pieces in the original packet he used his own discretion in making the selection of the part to be mounted and the part to be left. 8 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. When there were included in the original packet specimens from different hosts or different localities, in some cases representing dif- ferent species, it would have been difficult, if not impossible, to de- termine which was the original material from which Schweinitz's description was made. At the same time, Dr. Michener, in case the specimen was not too scanty, evidently took a small portion of it for his own herbarium. Michener's catalogue of his herbarium lists Spkaeria gyrosa Schw. Consulting his collection it is found that No. 1431, the number of Schweinitz's specimen, is missing. Pin holes in the mounting sheet, however, show that the specimen which was once there has been removed. • As perhaps throwing some light on the possible location of this specimen, it may be said that a speci- men apparently typical S. gyrosa, pycnidial form on beech, labeled by Dr. William Trelease as Sphaeria gyrosa from Pennsylvania, was seen in the Boissier Herbarium, Geneva. Dr. Trelease tells the writers that this specimen probably came from Dr. Michener, and as there is no evidence that Dr. Michener or any one else has col- lected E. gyrosa in Pennsylvania there is considerable probability that this specimen represents a portion of Schweinitz's original col- lection. In most cases all of the material in Schweinitz's original species packets was removed and either mounted or distributed. This was the case with Sphaeria gyrosa. The original packet of Schweinitz, which was fortunately preserved with all the others, is empty and apparently a part at least of the specimen which it contained is found in the mounted collection as prepared by Michener. This consists of a single piece of bark shown in Plate VI, figure 1. From the evidence the writers have been able to gather from Schweinitz's manuscripts and correspondence, as well as from studies of his writ- ings and specimens in other herbaria, it appears that this specimen is the one indicated on the original packet and also by Schweinitz (74, p. 206) as having been collected in New England and sent to him by Torrey. This, as shown by his correspondence, was after he had left North Carolina. The bark upon which the fungus grew is clearly not Fagus, Juglans, or Quercus, the hosts originally given for S. gyrosa, but apparently Acer. It is therefore not a part of the original specimens from Salem, N. C., upon which his description was based, and in reality is not Sphaeria gyrosa, but a species of Nectria, which Schweinitz incorrectly identified as S. gyrosa. Por- tions of this same specimen are found in Berkeley's herbarium at Kew and in the Curtis herbarium at Harvard. They are clearly the Nectria referred to above from Torrey. In this connection, it may be noted that E. Hitchcock in 1829 (42, p. 63) reports Sphaeria gyrosa Schw. from Amherst, Mass., and states in the preface to his list that Dr. Torrey assisted in the determination of the cryptogams. Bui. 380, U. S. Dept. of Agriculture. PLATE I. : CANKERS" CAUSED BY ENDOTHIA PARASITICA ON CASTANEA DENTATA. X Bui. 380, U. S. Dept. of Agriculture. PLATE II. HERB. MUS. PARIS , ( Ex. herb. Ad. Brongniart. Anno 1843 ) FIG. 1.— PERITHECIA AND PYCNIDIAL STROMATA OF ENDOTHIA PARASITICA WITH CANKERS ON CASTANEA DENTATA. FIG. 2.— COTYPE OF SPHAERIA GYROSA SCHW. ON FAGUS. Specimen now in the Paris Museum sent to Brongniart by Schweinitz, showing Tulasne's label "Melogramma gyrosum" and Schweinitz's autograph label. Bui. 380, U. S. Dept. of Agriculture. PLATE III. ee-t.£f<^ £&tfr ,///, -'/.7x J?X. A SHEET FROM THE MOUNTED PORTION OF SCHWEINITZ'S HERBARIUM AT THE PHILADELPHIA ACADEMY OF SCIENCES, SHOWING SPECIMENS AS PREPARED AND LABELED BY MICHENER. Bui. 380, U. S. Dept. of Agriculture. PLATE IV. , A SHEET FROM MICHENER'S HERBARIUM, SHOWING A PART OF SCHWEINITZ'S TYPE OF PEZIZA CINNABARINA (UPPER RIGHT HAND CORNER); ALSO SHOWING CLEARLY THAT THE MOUNTING AND LABELING OF THIS AND SCHWEINITZ'S COLLECTION WERE DONE BY THE SAME PERSON. ENDOTHIA PARASITICA AND RELATED SPECIES. 9 This seems to explain the origin of the specimen which Schweinitz received from Dr. Torrey. The writers have searched in vain for Endothia gyrosa in Amherst and vicinity and they know of no col- lections of the fungus from Massachusetts. No specimens upon which Hitchcock's list was based have been located. Since it can be clearly shown that little or none of the original type collection of this species is in the Philadelphia Academy col- lection it must be looked for elsewhere. It is found by reference to Schweinitz's correspondence and manuscripts, which have been care- fully examined by the writers through the courtesy of 'the Phila- delphia Academy and the descendants of Schweinitz, and also by studies in foreign herbaria that he divided his specimens with many of his European and American correspondents. As he does not ap- pear to have kept any duplicates separate from his regular collection it seems probable that the specimens he distributed were taken from the original packets. Thus in some cases, apparently all of a type specimen was removed from the original packet. In fact, in one instance (73, p. 5) he states that he sent his only specimen of a species of Hypoxylon to Dr. Schwaegrichen, of Leipzig. It seerns rather certain from statements made by Schwaegrichen in his introduction to Schweinitz's paper on the fungi of North Carolina (72) that specimens of a large number, if not all, of the species represented in that work were sent to him. The types or parts of the types should therefore be found in Schwaegrichen's herbarium. In spite of all their efforts, however, through correspond- ence and personal search in Europe, the writers have been unable to locate Schwaegrichen's collection of fungi. They found, however, in the herbarium of the University of Leipzig a small bit of a speci- men labeled "Sphaeria gyrosa Schwein. Juglans Fagus Carolina D. Schwaegrich. dd 5-21 K. Z." This specimen is evidently a part of the original collection of Schweinitz which was sent to Schwaeg- richen and given by him to Dr. Kunze. The host is apparently neither Juglans nor Fagus, but seems to be Quercus. It may be noted in this connection that in spite of diligent search by the writers and various other collectors no specimen of Endothia has yet been found on Juglans in this country. Neither have the writers been able to find any specimen in the various herbaria examined. They have concluded, as a result of their studies, that the mention of Juglans by Schweinitz was an error in the identification of the host, which it is believed was really Quercus, the host upon which E. gyrosa is most frequently found in the South, and especially in the vicinity of Salem. According to the American Code,1 however, the specimen which should be taken as the type in this case is the one on 1 American Code of Botanical Nomenclature. Canon 14, b. Bulletin, Torrey Botanical Club, vol. 34, p. 172. 1907. 10 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. Fagus, as this is the first-mentioned host in the original description. No specimen of this species on Fagus from Schweinitz was found in Kunze's collection. However, authentic specimens from Schweinitz on Fagus have been found in Fries's herbarium at Upsala, in Hooker's herbarium at Kew, and in Brongniart's herbarium in the Paris Museum. The last, which is the largest and best specimen, is shown in Plate II, figure 2. Microscopic studies of the specimens at Paris and Kew show only pycnidia with pycnospores. The writers were unable to examine microscopically the specimen in Fries's herba- rium, but k agreed in all macroscopic respects and also, so far as could be determined with a hand l«is, with the Paris and Kew speci- mens. These specimens agree with all the material collected on Fagus from various localities in the South. Studies of numerous collec- tions of E. gyrosa have shown that the pycnidial form can be dis- tinguished with certainty from any of the other species of Endothia at present known. The connection between this pycnidial form and the perithecial form as described has been demonstrated by pure cultures from ascospores and also by the association of typical pycnidia and pycnospores with perithecia and ascospores in the same stroma. There appears to be no reasonable doubt, therefore, that the specimens collected by Schweinitz on Fagus were the pycnidial form of Endothia gyrosa^ and the specimen in the Paris Museum which was sent by Schweinitz to Brongniart about 1825 may properly be considered a cotype of Schweinitz's species. The specimen from Schweinitz in Kunze's herbarium at Leipzig also proves on microscopic examination to be the pycnidial form of the same fungus. It is probable from the evidence at hand that Schweinitz did not collect any specimen showing ascospores of this fungus. However, the specimen in Kunze's herbarium shows some perithecia evidently immature and without spores. A part of the specimen from Schweinitz in Fries's herbarium showrs stromata on a piece of bark, evidently not Fagus, but probably Quercus. This also appears to be pycnidia only. The specimen referred to by Clinton (18), which was found in the original packet of Schweinitz at Philadelphia with Spkaeria enteromela, is also undoubtedly the pycnidial form of E. gyrosa, which closely resembles some early stages in the development of species of Hypoxylon, especially H. enteromela. These species may be easily confused with each other, and this would seem to be a probable explanation of the accidental presence of this specimen in this packet. Another point of interest in this connection is the fact that in spite of diligent search on the part of the writers and many other collectors and an examination of numerous specimens of En- dothia on Fagus in all stages of development and from different localities only Endothia gyrosa has been found on this host. Of ENDOTHIA PARASITIC A AND RELATED SPECIES. 11 course, it can not be positively stated that E. ftuens does not occur on Fagus in this country, but if it does it must be rare. In this con- nection, it is also perhaps worthy of note that, notwithstanding the mention of Fagus as a host in Europe, the writers have never seen any European specimens of Endothia on this host. The specimens so named by Roumeguere and distributed as No. 989 Fun. Gal. on beech are, according to several specimens examined, evidently a young condition of some Hypoxylon, probably H. coctineum, which in this state bears a superficial resemblance in form and color to the stromata of Endothia, but can be easily distinguished by the dark- brown or blackish color of the interior of the stroma. The identity of Schweinitz's Sphaeria gyrosa with the long ascospore form of Endothia shown on Plate VII is based on careful microscopic study of the stromata and measurement of the pycnospores from four specimens of the original collections of Schweinitz in North Carolina, three on Fagus and one labeled Juglans. The three on Fagus show the typical pycnidial stromata and pycnospores of the species, either of which is sufficient for positive identification when thoroughly known. The specimen referred to by Schweinitz as on Juglans also shows typical pycnospores of E. gyrosa. The evidence, as stated above, leaves no reasonable doubt as to the identity of the fungus which Schweinitz described as Sphaeria gyrosa. According to a specimen wThich is probably a portipn of Schwei- nitz's type found in Michener's herbarium, Peziza dnnabarina Schw. is the pycnidial form of E. gyrosa (Schw.) (See PL IV.) It is the form with small pycnidia on bare wood of Liquidambar. This was first reported by Schweinitz as " Peziza flammea A. and S." and later changed as above. Later Saccardo (69, vol. 8, p. 399), thinking that this was a Discomycete, transferred it to the genus Lachnella. The other American species of Endothia which was described by Schweinitz as Sphaeria radicalis and first published by Fries in 1828 (31, p. 73) has also until recently been more or less misunderstood. The only specimens of this species found at present in Schweinitz's mounted collection at the Philadelphia Academy of Science is a small piece of bark of an oak root bearing a few pycnidial stromata. No host was given in Fries, but Schweinitz in 1832 (74 p. 197) gives Fagus as the host. That this was an error and that the host was really Quercus and not Fagus is clearly indicated by all of Schwei- nitz's specimens examined, not only those in the Philadelphia Academy but those found in several herbaria in Europe and one in Curtis's herbarium at Harvard, and also in Schweinitz's autograph label on the original packet in his herbarium. A photograph of this packet is shown in Plate VI. The description of this species was first published by Fries in 1828 (31, p. 73). Schweinitz's specimen at the Philadelphia Academy 12 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. shows only pycnidia. (See PL V, fig. 2.) His description, how- ever, as well as his unpublished illustrations preserved in the library of the Academy, show clearly that perithecia were present in the material from which the description was made. This is also con- clusively shown by authentic specimens from Schweinitz in at least two European collections, those of Fries at Upsala and Hooker at Kew. A microscopic examination of these specimens shows good perithecia and mature ascospores having the characters and meas- urements given elsewhere in this paper for Endothia fluens (Sow.). (See PL XVII, fig. 9.) ' As there is no indication in Schweinitz's writings or in his manuscript nofes and records that he made more than one collection of this species, there is no reason to doubt that the material at Upsala and Kew is a part of that upon which he based his description of Sphaeria radicalis Schw. The true type specimen of the species is that in Fries's herbarium upon which he based his description, which was added to the diagnosis sent by Schweinitz. One year after the description of this species from America it was reported from Italy by Rudolph, in 1829 (66, p. 393), and in 1830 Fries (32, p. 541) himself reports the fungus from France. This species had, however, been collected and described before in its pycnidial condition in 1814 by Sowerby (79, pi. 438) under the name of Sphaeria fluens. This was reported in 1836 by Berkeley (8, p. 254) as Sphaeria gyrosa Schw. A microscopic study of the original material of this species, which was collected by Charles Lyell on chestnut in the New Forest in southern England and is now preserved in the Kew Herbarium, leaves no doubt that it is the pycnidial form of Endothia radicalis (Schw.). Plate XVII, fig- ure 3, shows pycnospores from Sowerby's specimen at Kew. This specimen agrees with Sowerby's illustration and is apparently the l t+t C^,f t-*. ' /' ' m •X- i y f^c*-T.tjff ' / . /&?tt> /l k/^v: ts//t FIQ 1 -PHOTOGRAPH OF SCHWEINITZ'S MANUSCRIPT NOTES, WITH His DESCRIPTION OF SPHAERIA RADICALIS/ FIG. 2.-SPECIMEN OF S. RADICALIS IN THE MOUNTED COLLECTION OF SCHWEINITZ, AS PREPARED BY MICHENER? ALSO ORIGINAL PACKET WITH SCHWEINITZ'S AUTOGRAPH LABEL. Bui. 380, U. S. Dept of Agriculture. PLATE VI. -• T FIG. 1.— PHOTOGRAPH OF THE SPECIMEN IN SCHWEINITZ'S HERBARIUM MOUNTED BY MICHENER. NOT TRUE ENDOTHIA GYROSA BUT A NECTRIA. FIG. 2.— ORIGINAL PAPER PACKET IN WHICH SCHWEINITZ'S TYPE MATERIAL OF E. GYROSA WAS PRE- SERVED, WITH His AUTOGRAPH LABEL. Bui. 380, U. S. Dept. of Agriculture. PLATE VII. ENDOTHIA GYROSA GROWING ON THE RECENTLY CUT END OF A LIVING BRANCH OF FAGUS SP. NATURAL SIZE. Bui. 380, U. S. Dept. of Agriculture. PLATE VIII. MYCELIAL FANS OF ENDOTHIA PARASITICA UNDER THE BARK OF CASTANEA DENTATA. Illustration from Heald (39), by courtesy of I. C. Williams, Pennsylvania State Forestry Department. ENDOTHIA PARASITIC A AND RELATED SPECIES. 17 SYNONYMS — Continued. Perithecia — Continued. Sphaeria radicalis Schw., 1832, Fun. Am. Bor., p. 197. Sphaeria radicalis Schw., Mont., 1834, in Ann. Sci. Nat. Bot, s. 2, t. 1, p. 295. Sphaeria (Diatrype) radicalis Fries, Currey, 1858, in Trans. Linn. Soc. London, v. 22, pt. 3, p. 272, pi. 47, fig. 89. p. p. Valsa radicalis Ces. and De Not., 1863, in Comm. Soc. Crittog. Ital., v. 1, p. 207. Endothia radicalis (Schw.) Ces. and De Not., 1863, in Comm. Soc. Crittog. Ital., v. 1, opp. p. 240. Melogramma gyrosum L. R. and C. Tul., 1863, Selecta Fung. Carpol., t. 2, p. 87. p. p. max. Sphaeria (Diatrype) radicalis Schw., Currey, 1865, in Trans. Linn. Soc. London, v. 25, pt. 2, p. 244. Endothia gyrosa (Schw.) Fckl., Sacc., 1882, Syll. Fung., v. 1, p. 601. p. p. Endothia gyrosa var. rostellata Sacc., 1882, Syll. Fung., v. 1, p. 602. Endothia radicalis (Schw.) Wint, 1887, Pilze, p. 803. Endothia gyrosa Schw., Ell. and Ev., 1892, No. Amer. Pyren., p. 552. p. p. Endothia mrginiana P. J. and H. W. And., 1912, in Phytopathology, v. 2, no. 6, p. 261. Endothia gyrosa (Schw.) Fries, Clint., 1913, in Conn. Agr. Exp. Sta. Rpt, 1911-12, p. 425. Endothia pseudoradicalis Petri, 1913, in- Atti R. Accad. Lincei Rend. 01. Sci. Fis., Mat. e Nat., s. 5, v. 22, sem. 1, fasc. 9, p. 654. Endothia gyrosa (Schw.) Fckl., Hohnel, 1913, in Sitzber. K. Akad. Wiss. [Vienna], Math. Naturw. Kl., Abt. 1, Bd. 122, Heft 2, p. 298. TYPE SPECIMEN. — Sowerby in Herb. Kew. on Castanea sativa, New Forest, England. Coll. C. Lyell, Apr. 15, 1809. PYCNIDIA. — Stromata corticular or subcorticular, truncate conical to pulvi- nate, usually separate and gregarious, but frequently confluent, 0.75 to 3 mm. in diameter by 0.5 to 2.5 mm. high, compact, varying from light auburn to chestnut on the surface and capucine yellow to cadmium orange within; pycnidia consisting of simple or more or less complex and irregular chambers in the stroma, opening by an irregular pore or slit at the apex of the stroma ; sporophores usually simple, sometimes branched near the base, cylindric to subclavate, 10 to 13 /* long, sometimes 24 to 30; pycnospores oblong to rod- like, pale yellowish in mass, 3 to 5 by 1.5 to 2 //,, mostly 3.5 to 4 by 2 jt. PERITHECIA. — Stromata the same or similar to those producing pycnidia; perithecia membranous, few to many, mostly 15 to 25, 300 to 400 /* in diameter, usually arising in the lower portion of the stroma, irregularly arranged in one to three layers, prolonged into slender necks which penetrate the stroma above and protrude usually from 300 to 600 /w, terminating in conical ostioles ; asci oblong fusoid or subclavate, very short stipitate, 30 to 40 by 6 to 8 /t, mostly 30 to 35 by 7 /*, ascospores irregularly biseriate, oblong fusoid or subellipsoid, not constricted at the septum, hyaline with a thin gelatinous envelope, 6 to 10 by 3 to 4.5 /*, mostly 6.5 to 9 by 3 to 4 p. CULTURAL CHARACTERS. — Cultures one month old on white corn meal show a compact growth with a nearly smooth surface. The color ranges from light cadmium to empire yellow, and the medium becomes perilla purple. Pycnidia and spores usually appear a little later, forming large erumpent stromata which extrude thick masses of pycnospores. The light mycelium with large 43737°— Bull. 380—17 2 18 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. pycnidial stromata and spore masses are distinguishing characters on this medium. HOSTS. — America : Exposed roots and branches of Q. alba, Q. coccinea, Q. marylandica, Q. prinus, Q. rubra, Q. velutina, and Castanea dentata. Europe: Specimens examined, Quercus pedunculata, Castanea sativa, Alnus glutinosa, Ulmus campestris, Carpinus betula, and Corylus sp. Japan: Castanea sp. and Pasania sp. It is also reported on Aesculus, Fagus, and Juglans by Traverse. TYPE LOCALITY. — New Forest, England. GEOGKAPHICAL DISTBIBTJTTON. — America: Southern Pennsylvania and Ohio to South Carolina and northern Mississippi. Europe: Southern England, France, South Germany, and Switzerland to southern Italy and Transcaucasia. Asia: Japan. ILLUSTRATIONS. — Sowerby, 1814, Col.^Fig. Engl. Fungi, Sup., pi. 438; Currey, 1858, in Trans. Linn. Soc. London, v. 22, pt. 3, pi. 47, fig. 89 (2 upper spores) ; Ces. and De Not., 1863, in Comm. Soc. Crittog. Ital., pi. 3 ; Sacc., 1873, in Atti Soc. Veneto-Trentina Sci. Nat. Paclova, v. 2, fasc. 1, pi. 14, fig. 63-65 ; Sacc., 1883, Gen. Pyren., pi. 6, fig. 6 ; Ruhl., 1900, in Hedwigia, Bd. 39, pi. 2, fig. 10 ; Trav., 1906, in Soc. Bot. Ital. Fl. Ital. Cript, pars 1, v. 2, fasc. 1, p. 180, fig. 34 ; P. J. and H. W. And., 1913, in Penn. Chestnut Tree Blight Com. Bui. 4, p. 22, fig. 2, A and C ; Clint, 1913, in Conn. Agr. Exp. Sta. Rpt, 1911-12, pi. 28, fig. b, e, h, and j ; Petri, 1913, in Atti R. Accad. Lincei Rend. Cl. Sci. Fis., Mat. e Nat, v. 22, sem. 1, fasc. 9, p. 656, fig. 1-3. EXSICCATI. — Pycnidia : Thiim. Myc. Univ., 769, on Castanea ; Sacc. Myc. Ven., 670, on Carpinus betula; Sacc. Myc. Ven., 929, on Castanea. Perithecia : Fckl. Fun. Nass., 640, on Ulmus campestris; Erb. Critt. Ital., 986, on Castanea; Rab. Herb. Viv. Myc., 254, on Castanea. Roum. Fun. Sel. Gal., 989, labeled Endothia gyrosa Schw. on beech is appar- ently young Hypoxylon coccineum. The most important synonyms given here have already been dis- cussed. Of the others the writers have examined the types or col- lections upon which the identifications were based. All the material of Endothia in the herbaria of Cesati, De Notaris, Fuckel, and Berkeley, as well as other smaller collections, has been carefully studied. E. virginiana And. and And. has been studied in cultures, as well as typical specimens from the authors of the species, and agrees in every particular with E. fluens. Through the kindness of Dr. Petri a part of the type of his E. pseudoradicalis has been examined, but unfortunately no cultures could be obtained from the specimen. The writers have been unable to distinguish his specimen from forms of E. fluens which appear to show all the intermediate conditions of variation connecting it with typical E. fluens. The ascospores of E. fluens are more variable in size and shape than those of any other species of Endothia studied. After examining many specimens of this species from Europe, it does not seem possible at present to separate any of them. The case of E. pseudoradicalis can not perhaps be regarded as closed until more material of it has been collected and compared in culture. In fact, the slide from the type of Sphaeria radwalis Schw. shows ascospores of both the narrow and broad form. The photomicro- ENDOTHIA PARASITICA AND RELATED SPECIES. 19 graph, Plate XVII, fig. 9, shows an ascospore which agrees with Petri's description and figures. ENDOTHIA FLUENS MISSISSIPPIENSIS S. and S. nov. comb. SYNONYM : Endothia radicalis mississippiensis Shear and Stevens in U. S. Dept. Agr., Bur. Plant Indus. Cir. 131, p. 4. 1913. TYPE SPECIMEN. — No. 1782, on Castanea dentata, Blue Mountain, Miss., N. E. Stevens, Feb. 13, 1913. Deposited in Pathological and Mycological Collec- tions, Bureau of Plant Industry. CULTURAL CHAKACTEHS. — Cultures one month old on white corn meal show a compact, rather uniform surface, the color of the mycelium varying from cad- mium orange to xanthine orange. This variety is distinguished from the species by the color of its mycelium, by the numerous small pycnidia thickly scattered over the surface of the culture, and by the lack of any purple color in the medium. HOSTS. — Castanea dentata, Quercus alba, and Q. velutina. GEOGKAPHICAL DISTRIBUTION. — Northern Mississippi, Kentucky, Tennessee. COLLECTIONS EXAMINED. — On Castanea dentata: No. 1706 A. pycnidia, Corinth, Miss., T. E. Snyder; no. 708, pycnidia, Dumas, Miss., T. E. S. ; no. 1782, ascospores, Blue Mountain, Miss., N. E. S. ; no. 1806, ascospores, Blue Moun- tain, Miss., N. E. S. On Quercus : No. 1989, pycnidia, Danville, Ky., N. E. S. ; no. 1995, pycnidia, Danville, Ky., N. E. S. ; no. 2032, pycnidia, Lexington, Tenn., N. E. S. ; no. 2255, pycnidia, Sardis, Miss., S. and S. No morphological characters have yet been found to distinguish this variety. It is therefore separated on its cultural characters, which are marked and constant. The plant was first collected by T. E. Snyder, of the Bureau of Ento- mology. ENDOTHIA LONGIROSTRIS Earle, 1900, in Muhlenbergia, v. I, no. 1, p. 14. SYNONYM : Perithecia : Diatrypc radicalis ( Schw. ) Fries, Mont., 1855, in Ann. Sci. Nat. Bot. 4, t. 3, p. 123. Not Schw. TYPE SPECIMEN. — No. 4340. A. A. Heller, Plants of Porto Rico. In Herb. N. Y. Bot. Garden. PYCNIDIA. — :Stromata corticular, erumpent, gregarious, sometimes confluent, 1 to 3 mm. in diameter, subcoriaceous, surface orange rufous to chestnut, in- terior zinc orange ; pycnidia consisting of irregular labyrinthiform cavities open- ing by a single large pore or irregular rupture at the apex of the stroma ; sporophores slender, somewhat tapering upward, mostly 8 to 10 p long; pycno- spores oblong elliptic, hyaline or yellowish in mass, when expelled forming a stout spore horn or tendril, colored like the stroma on the outside, 2 to 4 by 1 to 1.5 p. PEEITHECIA. — Stromata the same as those producing pycnidia, but larger and frequently confluent, forming linear series in crevices in the bark; perithecia arising usually at the base of the pycnidial stroma, mostly 3 to 10 in the sepa- rate stromata, membranous, 300 to 400 p in diameter, mostly in a single irregu- lar series, prolonged into long necks, 1.5 to nearly 1 cm. long, sec. Earle, inter- nally black, externally same color and structure as the stroma; ostiole acute; asci oblong cylindric to fusiform, 25 to 35 by 5 to 7 p, mostly 30 by 6 p ; asco- spores overlapping uniseriate to irregularly biseriate, hyaline, ovoid to ovoid elliptical, 6 to 8.5 by 3 to 4 p, mostly 7 to 7.5 by 3 to 3.5 p. 20 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. CULTURAL CHAEACTERS. — Cultures one month old on white corn meal have a uniform cadmium orange to xanthine orange color. The entire surface is covered with a compact growth, irregularly ridged. Tiny mars orange spore masses are scattered irregularly over the surface. Cultures of this species closely resemble E. fluens mississippicnsis on this medium, being distinguished by the smaller and much less numerous spore masses. The medium is changed to amber brown just below the mycelium, shading into mars yellow; whereas, in the case of E. fluens mississippiensis the color of the medium is very little changed. TYPE LOCALITY. — " Calcareous hills east of Santurce, Porto Rico, altitude 10 ft." GEOGRAPHICAL DISTRIBUTION. — Porto Rico and French Guiana. EXSICCATI. — Pycnidia and perithecia : Heller, Plants of Porto Rico, no. 4340. This species, which appears to be subtropical or tropical in its range, is known at present from only three collections, the type col- lection from Porto Rico, a collection by Prof. N. Wille, No. 816, Porto Rico, distributed by the New York Botanical Garden, from which the cultures were obtained ; and one made by Leprieur, No. 392, in French Guiana, and determined by Montagne as Diatrype radicalis (Schw.). A specimen of this collection apparently labeled by Mon- tagne and preserved in the Delessert Herbarium at Geneva has been examined and found to agree with the type material of E. longiros- tris. It is readily distinguished from E. troplcalis by its smaller asco- spores and pycnospores, and from E. -fluens by its narrower and more acute ascospores and the long, slender necks of the perithecia. ENDOTHIA TROPICALIS Shear and Stevens sp. nov. SYNONYMS : Diatrype gyrosa Berk, and Broome, 1875, in Jour. Linn. Soc. [London], v. 14, p. 124. Nectria gyrosa Berk, and Broome, 1877, in Jour. Linn. Soc. [London], v. 15, p. 86. Cry phone ctria gyrosa (Berk, and Broome) Sacc., in Syll. Fung., v. 17, p. 784. 1905. Endothia gyrosa (Schw.) Pckl., Hohnel, 1909, in Sitzber. K. Akad. Wiss. [Vienna], Math. Naturw. Kl., Abt. 1, Bd. 118, Heft 9, p. 1480. TYPE SPECIMEN. — No. 2807 S. and S., on Elacocarpus glandulifcr, Hakgala, Ceylon, Coll. T. Fetch, August, 1913. PYCNIDIA. — Stromata corticular, pustular to pulvinate, usually gregarious or scattered, rarely confluent, 1 to 5 mm. in diameter, early becoming friable, orange chrome when fresh to sanford brown when old and weathered ; pycnidia consisting of numerous irregular cavities in the stroma ; sporophores mostly simple, clavate, tapering above, 6 to 10 /A long. ; pycnospores continuous, oblong to cylindric, very variable in size and shape, pale yellowish in mass, 3.5 to 7 by 1.5 to 2.5 /». PERITHECIA. — Stromata the same or similar to those bearing pycnidia ; peri- thecia black, membranous, collapsing when dry, 5 to 50 or more in a stroma ; 250 to 500 M diameter, irregularly arranged in one to three layers, bearing slender necks which penetrate the stroma and project 0.25 to 1 mm., termi- nating in acute ostioles; asci oblong or subclavate, nearly sessile, 40 to 50 by 7 /*; ascospores irregularly biseriate, subelliptical, obtuse, not constricted at ENDOTHIA PARASITICA AND RELATED SPECIES. 21 the septum, hyaline with a gelatinous envelope, 7.5 to 10.5 by 3.5 to 5 /*, mostly 8 to 10 by 4 to 4.5 /*. CULTURAL CHARACTERS. — Cultures one month old on white corn meal show small numerous, thickly scattered pycnidia and spore masses very similar to E. parasitica. The mycelium is orange buff to apricot orange. This species differs from E. parasitica in culture, chiefly in the brighter color of its mycelium. HOST. — Rotten logs and stumps of Elaeocarpus alandulifcr. TYPE LOCALITY. — Hakgala, Ceylon. GEOGRAPHICAL DISTRIBUTION. — Only known from Ceylon at present. One other collection of this species, No. 290 G. H. K. T. [Thwaite], N. Eliya, Ceylon, 6,000 feet, has been examined in the Kew Herbarium. Through the kindness of Mr. T. Fetch, of Peredeniya, the writers have received two large collections of this fungus. Some of the material was in a living condition and enabled the writers to obtain pure cultures for comparison with the other species of' Endothia. This species is closely related to E. parasitica, but is readily sepa- rated by its larger ascospores and larger and more variable pycno- spores and its nonparasitic habit. ENDOTHIA PARASITICA (Murr.) P. J. and H. W. And., 1912, in Phytopathology, v. 2, no. 6, p. 262 SYNONYMS : Diaporthe parasitica Murrill, 1906, in Torreya, v. 6, no. 9, p. 189. Valsonectria parasitica Rehm, 1907, Asc. Exs., no. 1710. Valsoncctria parasitica Rehm, 1907, in Ann. My col., v. 5, no. 3, p. 210. Endothia gyrosa var. parasitica Clint. 1912, in Science, n. s., v. 36, no. 939, p. 913. Endothia gyrosa (Schw.) Fckl. Hohnel, 1909, in Sitzber. K. Akad. Wiss. [Vienna], Math. Naturw. Kl., Abt. 1, Bd. 118, Heft 9, p. 1480. TYPE SPECIMEN. — Herbarium N. Y. Bot. Garden, on Castanea dentata, Bronx Park, New York City, Nov. 26, 1905, Coll. W. A. Murrill. PYCNIDIA. — Stromata corticular, slightly erumpent to truncate conical, usually separate and gregarious, frequently confluent in more or less linear series especially in old rimose bark, 0.75 to 3 mm. in diameter by 0.5 to 2.5 mm. high, varying from capucine yellow when young to auburn when old and weathered ; pycnidia consisting of irregular cavities in the stroma, 100 to 300 p in diameter ; sporophores mostly simple, subclavate, acute at the apex, usually 12 to 20 by 1.5 /*, more elongated filaments sometimes reaching 50 /u or more being frequently found among the normal sporophores; pycnospores, oblong to reya, v. 8, no. 5, p. Ill, fig. 2 ; Petri, 1913, in Atti R. Accad. Lincei, Rend. Cl. Sci. Fis., Mat. e Nat, s. 5, v. 22 ; sem. 1, fasc. 9, p. 656, fig. 4; Heald, 1913, in Penn. Chestnut Tree Blight Com. Bui. 5, pi. 13; Clint. 1913, in Conn. Agr. Exp. Sta. Rpt, 1911/12, pi. 28, fig. c, f, i, and k ; P. J. and H. W. And., 1913, in Penn. Chestnut Tree Blight Com. Bui. 4, p. 22, fig. 2, B and D; P. J. And. and Rank., 1914, in N. Y. Cornell Agr. Exp. Sta. Bui. 347, p. 562, fig. 89. EXSICCATI. — Pycnidia and perithecia : Rehm, Asc., 1710 ; Wilson and Seaver, Asc. and Low. Fun., 3 ; Bart. Fun. Col., 2926 ; all on Castanea dentata. This species is closely related in its morphological characters to all the species of section 2 of the genus. It is most likely to be confused with E. fluens, but shows constant differences, though slight, in size and shape of ascospores. They are predominantly broader and more uniform in shape, as shown by the table of measurements on page 35. In its active parasitic condition on Castanea it can always be distinguished by the presence of the mycelial "fans" in the inner bark, as showyn in Plate VIII. It has been confused with E. gyrosa through an erroneous identification of that species. MORPHOLOGY AND DEVELOPMENT. MYCELIUM. By far the most striking mycelial character is the production by E. parasitica of yellow or buff fan-shaped formations of mycelium in the cambium and bark of the host. These " fans " vary from 1 mm. to 1 cm. or more in width, and are composed of radiating hyphse closely pressed together to form a continuous layer. (PL VIII.) So constant are these mycelial fans in their occurrence and so characteristic in their appearance that they furnish the most re- liable field character for distinguishing E. parasitim from related species and may quite properly be regarded as a specific character when the fungus is growing in living trees. Anderson and Anderson (2, p. 204) first called attention to the fact that these fan-shaped formations of mycelium are absent from E. fluens. Rankin (62, p. 248) states that when the fungus grows saprophytically or while the tree is dormant these fans are not pro- duced. Anderson and Rankin (6, p. 565) report that in inoculations ENDOTHIA PAKASITICA AND RELATED SPECIES. 23 on Quercus alba and Q. prinus, E. parasitica produced the typical mycelial fans. Anderson (1, p. 14) considers that the occurrence of these fans is associated with the parasitic habit of the fungus. In his opinion single hyphae do not possess the power of penetrating the living cells, but the fungus grows on the injured and dead cells about a wound until a quantity of mycelium is accumulated, when it "en masse pushes through the living tissues of the bark." This view is also held by Keefer (45, p. 193), who adds that "the action of the ad- vancing mycelial mats seems to be physical rather than chemical, and the cells are mechanically broken to pieces." Kankin, however, states (62, p. 248) that "The host cells, just in advance of the edges of the fan, are disintegrated and form a distinct gelatinous band, which can be seen with the naked eye." This observation suggests to the writers that some toxic or enzymatic action upon the cells of the host probably occurs before the cells are actually invaded by the fungus hyphse. Careful investigation of this point should go far toward determining the causes of the parasitism of this fungus. Whatever the cause or function of these fans, they are very characteristic, and the writers have found them invariably in diseased material of Castanea in America, as well as in that from China and in two specimens of E. parasitica on Quercus. A similar mycelial formation, fanlike in form,1 is produced by Armillaria mellea in the bark of roots attacked by this fungus. Ex- cellent specimens of the Armillaria mycelial fans have been pre- sented to the writers by Prof. Wm. T. Home, of the University of California. STROMATA. Under the name Melogramma gyrosum, in which they included specimens of both Endothia gyrosa and E. fluens, the Tulasnes (83, pp. 87-89) described the structure of Endothia in some detail. Their description was based chiefly on abundant local material of E. fluens collected on Carpinus ~betulus L. during several years, but they also used material sent by Guepin from western France, pycnidial ma- terial on chestnut from Italy, American material sent by Schweinitz to Brongniart and preserved in the Paris Museum, and specimens from Carolina sent by Berkeley. According to the Tulasnes (83, p. 87 )2 the stromata are "developed singly and emerge gradually as so many scattered points with fibers radiating in all directions, soon swell into a yellowish cone, rupture the epidermis above them, 1 Since this manuscript was completed a very similar mycelial formation has come to the writers' attention. As figured by Nowell (50), pi. 1, Rosellinia pepo, when growing under the bark of lime trees, forms mycelial fans resembling those of Endothia parasitica. 2 The portions in quotations are rather free translations of the authors' Latin. 24 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. and put forth a very blunt apex. All are composed of a corky, parenchymatous, very dense, soft yellow material. The mature ones attain a diameter of 3 to 4 millimeters and a height of 1 to 2 millimeters, and on the somewhat reddish, and finally rusty red to yellow top, they are marked by black points, the ostioles." The Tulasnes observed that before the stromata reached their full size the pycnidial cavities were formed within them, sometimes " widely open," sometimes "narrow labyrinthine," and that through one or many openings in the top of the pycnidia, the long, twisted, orange tendrils, composed of mucus, and innumerable thin linear spores were expelled. " Perithecia are* developed chiefly in stromata des- titute of spermogonia, or more often with only a few * * they arise very abundantly and irregularly, some barely buried in the yellow corklike substance, others lower down and seemingly located in the bark of the host itself." Although the Tulasnes included all their material under a single species, they noted that the pycnidial stromata of the American specimens (really EndotMa gyrosa) differed considerably from the European (E. fluens). In describing the former, they say (83, p. 88) "The American fungus is said to grow in the bark of Fagus and Juglans * * * as a whole it abounds with numerous, very small spermatia. Wherefore if it is very thinly sectioned, the pieces, examined with a compound microscope, show cavities just as if you had before your eyes the smallest Gautieria or Balsamia." The Tulasnes do not try to distinguish definitely between stroma and mycelium, but merely state that the stromata develop within the mycelium. Ruhland (67), who was the next writer to discuss the morphology of a species of Endothia, defines the various portions of the fungus body in detail. According to his definition (p. 16) a "stroma (in distinction from mycelium) is the sum total of that part of the vegetative portion of the fungus body, which, without serving ex- clusively for absorption, takes part in the formation of the fruit body." He sets aside Fuisting's (36, p. 185) division of the fungus body into an epistroma and a hypostroma, as essentially nothing but the distinction of " conidial layers " and " perithecial stroma.." Ruhland divides the fungus body into an ectostroma and an ento- stroma. The ectostroma grows " on the upper surface of the paren- chyma of the bark, between it and the periderm, and is composed of a generally wide-lumened plectenchyma which does not possess the power of absorption." This portion has the following functions: " The formation of the conidia, the opening and breaking off of the periderm, and the stimulation of the development of the entostroma." The entostroma, on the other hand, according to Ruhland, " lives in the parenchyma of the bark, and while young is in a high degree Bui. 380, U. S. Dept. of Agriculture. PLATE IX. ENDOTHIA GYROSA. VERTICAL SECTIONS OF STROMATA ON BEECH. X32. FIQ. 1 .—SHOWING NUMEROUS PYCNIDIAL CAVITIES ANDTWO MATURE PERITHECIA. FIG. 2.— SHOWING MATURE PYCNIDIA AND PERITHECIA SIDE BY SIDE. Except where otherwise indicated, the photomicrographs of stromata are from unstained sections cut with a freezing microtome. Bui. 380, U. S. Dept. of Agriculture. PLATE X. FIG. 1.— ENDOTHIA FLUENS. VERTICAL SECTION OF A STROMA FROM ITALY, SHOWIN'G YOUNG PERITHECIA IN A SINGLE LAYER. X 49. FIG. 2.— ENDOTHIA GYROSA. VER- TICAL SECTION OF A STROMA ON BEECH, SHOWING MATURE PYCNIDIA WITH MATURE PERITHECIA BELOW THEM, x 32. FIG. 3.— ENDOTHIA GYROSA. VERTICAL SECTION OF A PORTION OF A LARGE STROMA, SHOWING PERITHECIA IRREGULARLY ARRANGED IN SEVERAL LAYERS. Jul. 380, U. S. Dept. of Agriculture. PLATE XI. 9 8 >.* 5 " * '."Cl- * * '* - Wr> A^r^rAwi Bui. 380, U. S. Dept. of Agriculture. PLATE XII. ' ENDOTHIA PARASITIC A AND RELATED SPECIES. 25 capable of absorption, a power which it retains relatively perma- nently." In addition to its absorptive function the entostroma forms the pseudoparenchymatic cover for the perithecial walls. Ruhland studied herbarium material from the Royal Botanic Mu- seum of Berlin and specimens from Saccardo and Cesati, and de- scribed it under the name of Endothia radically (Schw.) Fr. (E. fluens of the present writers). He distinguishes an ectostroma, shaped like a truncated cone, consisting of fine, thin-walled hyphse, so closely interwoven that the wThole structure has a comparatively firm quality. Among these hyphse are crystals of calcium oxalate. As soon as this ectostroma breaks through the bark there is formed near the middle a short-lived 1-chambered pycnidium. Below this ectostroma (height 0.5 to 0.6 mm., diameter 0.7 to 1 mm.) the ento- stroma grows out as a mycelium through the upper portion of the bark. Ruhland says, " The entostroma with us does not produce per- ithecia, but remains wholly mycelial." He studied the perithecial stage in Cesati's specimens, however, and concludes that the peri- thecia originate without much change in the size of the entostroma and at a considerable distance, about 1 mm., below the ectostroma. The long necks then penetrate through the overlying entostroma and into the ectostroma to the base of the now functionless pycnidia. The upper portion of the ectostroma is then quickly killed and thrown off. Pantanelli briefly described the stromata of the genus Endothia, and pointed out several morphological characters which he considers distinctive of E. parasitica in contrast to E. -fluens. Aside from spore characters, which will be discussed later, Pantanelli (60, p. 870) con- siders that E. parasitica is characterized by numerous stromata, at first embedded in the bark, finally free; by pycnidial cavities numer- ous and irregularly arranged in various planes in the stromata deep in the bark; pycnidial stromata 1.1 to 1.2 mm. in height and 2.1 to 2.2 mm. in diameter; ascogenous stromata, height 1.8 to 2 mm., length 2.5 to 3.4 ; width, 3 to 3.2 mm. ; perithecia arranged in two or three layers; necks of perithecia averaging 1.25 mm., with inconspicuous ostioles ; walls of the perithecia uncolored or light brown. Endothia fluens, on the other hand, has isolated stromata, chiefly outside the bark; pycnidia aggregated, regularly arranged in a single superficial series; pycnidial stromata, height 0.4 to 0.5 mm., diameter 1.1 to 1.3 mm.; ascogenous stromata, height 1.1 to 1.4 mm., length 2.5 to 3.2 mm., width 1.2 mm. ; perithecia arranged in a single row ; necks of perithecia averaging 0.45 mm.; ostioles prominent; walls of the perithecia black. Anderson (1, pp. 17-24) described the development of the fructifi- cations of Endothia parasitica in detail. He studied the growth of 26 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. the pycnidia in pure culture and made sections of perithecial stro- mata growing on bark. According to Anderson, the pycnidium originates as a mass of densely intertwined hyphse, in the center of which numerous pycno- spores are cut off. The crowding of these spores increases the size of the pycnidial cavity and crowds the outer hyphse together to form a sort of wall. The ostiole is formed in the top by the loosening of the hyphse. The stroma always starts as a loose growth of hyphso around the pycnidium. It does not precede, but follows the first stages in the development of that organ. A fluffy growth of light- yellow mycelium surrounds the pycnidium and covers it over. If these are embedded and sectioned, they will be found to contain a loose tangle of undifferentiated hyphaB surrounding a central pyc- nidium. But as soon as the cork layer is broken the stroma under- goes a change. There is a rapid increase in size and at the same time a differentiation of the cells at the tips of those branches which reach the exposed surface. These cells now become shorter arid thicker, acquire heavier walls, and are densely crowded together, so that in cross section they appear as a pseudoparenchymatous tissue. The layer thus formed covers all the exposed surface of the stroma and also grows up around the necks of the perithecia. The stroma increases very rapidly in size and a mass of stromatic tissue is formed beneath the pycnidia, which are thus pushed out through the cork layer into the periphery. The primordia of the perithecia are formed usually in the tissues of the bark below the base of the original pycnidium, but at times are formed well up in the stroma. Usually 15 to 30 perithecia mature in a stroma. According to the writers' observations, the Tulasnes' description (83, pp. 87-89) is substantially correct so far as it goes. They, of course, placed pycnidial material of Endothia gyrosa in the same species with E. fluens, but, as already noted, they observed the dif- ference in the structure of the stromata and aptly compared the pycnidial stroma of E. gyrosa,, as seen in section, to a Gautieria. The division of the stroma into ectostroma and entostroma made by Euhland (67, p. 16) has, at least in the species of Endothia, no validity whatever. While it is true that pycnidia usually occur in the portion of the stroma first developed and perithecia often develop below them, this is by no means an invariable rule; and while stromata are developed which contain only pycnidia', other stromata apparently produce only perithecia or no spores whatever. Certainly no portion of the stroma can be distinguished which in- variably produces only perithecia or only pycnidia. On the con- trary, there is great variation in the relative position and time of appearance of the two types of fruiting structures. Also, while ENDOTHIA PARASITICA AND BELATED SPECIES. 27 the pycnidial cavity is sometimes small and simple, as described by Ruhland, it is more often large and much convoluted. (See Pis. XV and XVI.) While the writers, of course, agree with Pantanelli (60) that Endothia parasitica and E. fluens are distinct species, many of the stromatic characters which he describes are so variable as to be unreliable. In an examination of a large number of specimens the writers have been unable to find any constant difference in the ar- rangement or structure of the pycnidial stromata. This seems to depend chiefly in both species on the character of the bark and the moisture conditions. As to size, while the stromata of E. parasitica examined average somewhat larger than those of E. fluens, the range of the pycnidial stromata is about the same in the two species, vary- ing from 0.4 to 2 mm. in height and from 0.2 to 3 mm. in length. The ascogenous stromata are also very variable in size. Those measured by the writers varied in height from 0.5 to 2 mm. in En- dothia parasitica and from 0.5 to 2.3 mm. in E. fluens. In width the perithecial stromata were from 1 to 2.5 mm. in both species, while there is apparently no method for determining their length, since on thick-barked trees continuous narrow masses of perithecial stromata are often formed in the crevices of the bark. These stromatal masses frequently extend from 5 to 10 cm., and while they are in all prob- ability formed by the fusion of several stromata there is no way of determining how far each extends. The arrangement of the perithecia mentioned by Pantanelli (60) as a specific character seems to depend on the nature of the bark of the host. When the bark is thin and easily ruptured the stromata tend to spread out so that the perithecia occur in a single layer, while if the bark is thick and deeply ridged the stromata are thicker and the perithecia occur in two or more layers. That this is not a specific character is clearly shown by Plate XVI. Figures 1 and 3 of this plate show a stroma of E. parasitica and of E. fluens, respec- tively, both with three layers of perithecia, while Plate XVI, figure 2, and Plate X, figure 1, show stromata of both species with perithecia arranged in a single layer. Although, as already indicated, the stromata of each species are very variable, they are sufficiently distinct so that the native American species may readily be distinguished in the field. The stsomatic characters of Endothia gyrosa and E. singularis are much more distinct than those of .the other species. The stromata of E. gyrosa are erumpent, irregularly subglobose, with a rather roughened surface. They are usually from 1.5 to 2 mm. in height and vary from 1.5 to 3 mm. in width. The stromata of E. singularis are much larger than those of any other species of Endothia, being 28 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. usually from 2 to 4 mm. in length and 3 to 5 mm. or more in diameter. They are decidedly erumpent, rather regular, and subglobose in out- line. The contents of the stromata are brick red in color and are very powdery when old. The stromata of EndotMa fluens, E. fluens mississippiensis, and E. pamsitica resemble each other so closely that the species are prac- tically indistinguishable on this basis. All these species are char- acterized by partially embedded, confluent stromata which vary greatly in outline, depending on the nature of the bark of the host. As already stated, they vary from 0.4 to 2 mm. in height and from 0.7 to 5 mm. or more in length where confluent. E. tropicalis and E. longirostris resemble this group in their stromatic characters. Pycnidia. — The pycnidia of EndotMa gyrosa and E. singularis are very distinctive also. The pycnidial cavities of E. gyrosa are narrow and so irregularly convoluted that in a section of the stroma the cavities vary in width from 0.03 to 0.3 mm., averaging about 0.15 mm. On the whole, however, they are much narrower than those of E. fluens or E. parasitica. A section of a pycnidial stroma of E. gyrosa shows numerous irregular, rounded to elongate chambers separated by narrow walls. The pycnidial cavities of E. singularis (PL XIII) are minute, 0.03 mm. in diameter, nearly spherical, evenly distributed through the stroma and separated at first by com- paratively thick walls, which disintegrate and become powdery when the stroma is old. So far as the writers have been able to determine, the " tendrils " of pycnospores so characteristic of EndotMa fluens and E. parasitica are not formed in either E. gyrosa or E. singularis. Mature pycnidial stromata of E. gyrosa when placed in a moist chamber exude nu- merous droplets containing spores and scattered well over the surface of the stromata. The writers have been unable to produce any such change by placing the pycnidial stromata of E. singularis in moist chambers, and it seems probable that the pycnospores of E. singularis are set free by the breaking down of the outer walls of the stromata. As already mentioned, the inner partitions are friable, so the spores are readily scattered by the wind. The pycnidial cavities of EndotMa fluens and E . parasitica, and apparently all the other species of this section of the genus, vary from 0.2 to 0.3 mm. or more in diameter and may consist of a single chamber rather regular in outline (PL XIV, fig. 1) or of an irregular cavity consisting of many chambers (PL XV, fig! 3) more or less completely separated from one another. These species differ from E. gyrosa in that the pycnospores are usually discharged through a single opening near the top of the stroma and emerge in a single twisted tendril. ENDOTHIA PAEASITICA AND RELATED SPECIES. 29 Development of the stromata, — The writers have not followed the development of the stromata in culture, but an examination of nu- merous sections of Endothia singularis, E.gyrosa, E.fluens, and E. parasitica and a study of the three latter species under field condi- tions on various hosts shows that their development is by no means as uniform as indicated in Anderson's description (1). According to Anderson, the pycnidium develops first, and about the young pycnidium the stroma is quickly formed, while the perithecia arise later, usually in the lower portion of the stroma. This may perhaps be considered the typical course of development, and pycnidia are often found above the perithecia, but all variations occur. A large stroma may be developed without a sign of a pyc- nidium (PL XV, fig. 2). In some cases there is a considerable por- tion of the stroma above the pycnidial cavity (PL XIV, fig. 2), or the pycnidial cavities may be surrounded by a thick stroma (PL XIV, fig. 4, and PL XV, fig. 1). Sometimes, on the other hand, they are large and irregular, with little stroma (PL XV, fig. 3). The perithecia by no means uniformly arise below the pycnidia, but the two often occur side by side in the same stroma (PL IX, fig. 2; PL XIV, fig. 3; and PL XII). Sometimes, even, the perithecia are above the pycnidia (PL XIV, fig. 2). There seems to be no constant relation either as to the relative number of pyc- nidia or of perithecia in a single stroma. Sometimes the pycnidial portion is much larger (PL IX, fig. 1) ; sometimes the perithecia predominate (PL X, fig. 2) ; and sometimes the two portions are practically equal (PL XII). A like variability apparently occurs in the sequence of the fruit- ing bodies. As the figures show, the pycnidia sometimes develop after the perithecia; the reverse order is frequent; while in several sections (PL XII, and PL XIV, fig. 3) the two types of fruiting bodies were side by side and were producing mature spores abun- dantly at the same time. Just what factors determine the produc- tion of each type of spore or prevent or delay spore production is unknown. It seems probable, however, that climatic influences may prevent the development of ascospores in many cases. The action of climate may be very indirect, however, for no ascospores of any species have yet been obtained in artificial cultures, though En- dothia fiuens, E. fluens mississippiensis, E. tropicalis, and E. para- sitica produce pycnospores abundantly on a variety of media. Cer- tainly, climatic factors would not account satisfactorily for the fact that pycnidia and perithecia are produced at the same time in ad- jacent stromata, or even in different parts of the same stroma. The size of the perithecia is rather uniform in the various species (PL X, fig. 3, and Pis. XI and XVI), being about 0.35 mm. in diame- ter. They are typically globose to pyriform, but are usually more or 30 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. less irregular on account of crowding. This pressure may be so great as to produce almost any shape, and such perithecia some- times measure 0.5 mm. in the greatest diameter and 0.1 mm. in the shortest. SPORE MEASUREMENTS. The spore measurements recorded here were made by Miss Tiller. In the case of dried specimens, the spores were first soaked for three hours in lukewarm water and then mounted in the potassium- glycerine-copper medium, prepared according to the following formula : 1 part 2 per cent potassium acetate in water. 1 part 40 per cent glycerine in alcohol. Copper acetate sufficient to color. In the case of fresh specimens they were mounted directly in the same medium. - The measurements were made with a Zeiss filar eyepiece micrometer and a Zeiss 3 mm. 1.40 N. Ap. oil-immersion objective. Only approximate accuracy is claimed for these results, on account of the difficulty of overcoming the motion of the spores in a fluid medium. The results are, however, believed to be fairly comparable, as practically all were measured under the same condi- tions and treatment, and the margin of error is presumably rather uniform. The differences in size of pycnospores do not appear to be sufficient, however, to furnish diagnostic character for most of the species. The number of measurements of ascospores of EndotMa ftuens and E. parasitica is much larger than of the other species, as special attention was first given to these two species on account of their great similarity. In order to make the measurements of these species comparable to the others, the total number of spores of each length has been calculated in the percentage of the total number of spores measured. METHOD OF TABULATION. For better comparison, the spore measurements have been tabu- lated by half microns, all the spores in each specimen coming within 0.2 of a micron of each unit or half being grouped together; e. g., all the spores having a length of 7.3, 7.4, 7.5, 7.6, and 7.7 microns are included under the heading 7.5. The tables thus show at a glance the number of spores of a given length per specimen. The widths have been tabulated in the same way. For a better comparison of the shapes of the ascospores of EndotMa parasitica and E. fluens, the relative ratios of length to width in each spore have been calculated, the width being considered unity. The ratios of length to width were then tabulated by tenths ; that is, all the spores in each specimen having a ratio of length to ENDOTHIA PAKASITICA AND RELATED SPECIES. 31 width from 1.76 to 1.85 microns are included under 1.8. The rela- tive shapes of the spores in each specimen are thus clearly shown. TABLE I. — Measurements of pycnospores and asci of Endothia. PYCNOSPOEE MEASUREMENTS. Specimens. Number per specimen having the given length or width. Total. Lengths (microns). Widths (mi- crons). 2 2.5 3 6 5 in 3.5 4 4.5 5 5.5 6 6.5 < 1 1.5 2 2.5 Sphaeria gyrosa Schw. . Herb. Mus Paris 2 3 11 9 11 4 3 ? 9 5 5 15 11 18 5 8 6 8 7 2 1 1 9 17 19 4 g 26 17 24 14 25 25 12 16 14 25 25 S. gyrosa Schw. , Herb. Schwaeg. Endothia gyrosa on beech, Al- corn Miss No 1796 E singularis No 1939 4 6 8 6 3 5 4 2 6 4 11 12 5 8 1 5 11 E fluens Sowerby 6 5 2 1 E. fluens on chestnut, Fort Payne, Ala 1 1 2 4 1 1 E. fluens, Lugano, Switzerland. E. fluens mississippiensis, No. 1706A E. longirostris 2 3 i 6 8 3 I9 E tropicalis 6 6 3 1 3 2 4 19 13 3 E. parasitica, No. 1696 1 LENGTHS OF ASCI (MICRONS). -\jf. Nui nber p er spec imen ] laving thegi yen lei igth. 25 30 35 40 45 50 55 60 Total. Endothia fluens on Castanea 1702 2 8 11 1 22 Do. 1737 1 14 U 26 Do... 1741 5 6 11 Do . 1729 4 16 6 26 E. fluens on dead Castanea 1715 7 16 3 26 E. fluens on Castanea, Stresa, Italy E. fluens on Quercus 1656 1711 2 6 16 16 7 1 1 1 25 25 Do 1927 2 10 12 24 E. fluens mississippiensis, Blue Moun- tain, Miss 1806 5 14 3 22 E . parasitica on Castanea 1710 1 1 2 4 Do 1739 5 10 10 1 26 E. parasitica, China . 2151 2 14 4 4 3 27 E . gyrosa on Quercus 1709 1 7 8 E. gyrosa on Liquidambar 19 6 25 E. singularis. Palmer Lake, Colo 4 15 5 24 E. longirostris, Porto Rico . . 6 13 3 3 25 E. longirostris French Guiana 6 10 1 17 E. tropicalis 6 5 3 2 16 WIDTHS OF ASCI (MICRONS). Specimens. Number per specimen having the given width. Total. 4 5 6 7 8 9 10 Endothia gyrosa 8 2 2 1 2 7 3 2 10 11 12 11 10 11 9 10 10- 10 E singularis 1 8 6 6 6 2 3 2 1 4 4 2 E fluens America 2 3 6 7 6 4- tO tO E parasitica China E parasitica America 32 BULLETIN 380,, U. S. DEPARTMENT OF AGRICULTURE. PYCNOSPORES. The pycnospores of all the species are oblong elliptic to cylindric in shape and so small as to make accurate measurement very difficult. Slight but apparently constant differences in their size in certain groups of species may, however, be traced. These differences are clearly shown in Table I. Endothia gyrosa, E. singularis, and E. longirostris have smaller pycnospores than the other species, the most frequent lengths being 3 and 3.5 p. The pycnospores of E. singularis are slightly broader than those of E. gyrosa and E. longirostris, being 1.5 to 2 [/,, as against 1 to 1.5 y. in the last two species. Endothia fluens, E. fluens mississippiensis, and E. parasUica are even more closely similar in the size of their pycnospores than in that of their ascospores, the most frequent size being 4 by 2 \L. The pycnospores of E. tropicalis are much larger and more variable in size and shape than those of other species. They range from 3.5 to T [JL in length and from 1.5 to 2.5 \L in width. ASCI. The writers have not attempted a study of the origin and early development of perithecia or asci in any of the species of Endothia. Work on this subject has been published by Anderson and Rankin (6), for Endothia parasitica, but the nuclear phenomena and origin and development of the ascogenous hyphas are not yet entirely clear. The part termed a trichogyne by these authors seems more likely to be the initial stage in the development of the neck of the perithecium than the relic of an organ of fertilization. The asci appear almost or quite sessile in most species, and though varying considerably in size and shape, as indicated in Table I, are usually oblong elliptic or subclavate, having a sort of inner membrane inclosing the ascospores and some thin granular matter extending to the apex of the ascus, where a slight thickening appears, as described and illustrated by Anderson for Endothia parasitica. A similar condition is found in various species of Pyrenomycetes and probably functions in some way in connection with the discharge of the ascospores. The asci are generally wider and slightly longer in E. parasitica than in E. fluens and other members of section 2. The asci of E. gyrosa are shorter than those of any other species. E. tropicalis has the longest asci. The. asci of none of the species show a very wide range of variation, as Table I also indicates. PARAPHYSES. Most students of Endothia have reported paraphyses wanting in this genus. Anderson (1, p. 33, fig. 32) and*Anderson and Rankin (6, p. 579,, fig. 83) report paraphyses present and figure what they Bui. 380, U. S. Dept. of Agriculture. PLATE XIII. V *c «•.. !t$ti Lf i * &- + > , . -T'-- -tt . * rt* iPf -? "*'- < - : " • - • • * "^ " • !^V - • * '*• ^L-; f-,^r,^"- :^^^H--- mmtm^-. * ^ ENDOTHIA SINQULARIS. VERTICAL SECTION OF THE MAJOR PART OF A PYCNIDIAL STROMA. X 32. Paraffin section stained with Bismarck brown. Bui. 380, U. S. Dept. of Agriculture. PLATE XIV. ENDOTHIA FLUENS. VERTICAL SECTIONS. X 49. FIG. 1 .—SIMPLE PYCNIDIUM WITH VERY LITTLE STROMA, FROM ITALY. FIG. 2.— STROMA FROM ITALY, SHOWING A PERITHECIUM ABOVE A PYCNIDIUM. FIG. 3.— STROMA FROM AMERICA, SHOWING A MATURE PYCNIDIUM AND PERITHECIA SIDE BY SIDE. FIG. 4.— STROMA, SHOWING A SINGLE PYCNIDIUM AND FUNDAMENTS OF PERITHECIA BELOW. Bui. 380, U. S. Dept. of Agriculture. PLATE XV. ENDOTHIA PARASITICA. VERTICAL SECTIONS OF STROMATA. X 49. FIG. 1 .—SHOWING A YOUNG, SIMPLE PYCNIDIAL CAVITY AT THE BASE. FIG. 2.— IN WHICH NEITHER PYCNIDIA NOR PERITHECIA HAVE BEGUN TO DEVELOP. FIG. 3.— WITH IRREGULAR CHAMBERED PYCNIDIA. All the above are about the same age — four months after inoculation. Bui. 380, U. S. Dept. of Agriculture. PLATE XVI. v£vV;^?h KM ENDOTHIA PARASITICA AND E. FLUENS. VERTICAL SECTIONS OF STROMATA. X 20. FIG. 1.— E. PARASITICA. SHOWING PERITHECIA ARRANGED IN SEVERAL IRREGULAR LAYERS. FIG. 2.— E. PARASITICA, SHOWING PERITHECIA ARRANGED IN A SINGLE LAYER. FIG. 3.— E. FLUENS, FROM ITALY, SHOWING PERITHECIA ARRANGED IN SEVERAL LAYERS. ENDOTHIA PARASITICA AND RELATED SPECIES. 33 regard as an early stage of their development. They describe them as branching frequently and very crooked, extending around the perithecium as well as upward. The writers have searched in all the species studied for evidence of the presence of paraphyses, but have never seen anything resembling paraphyses as they occur in closely related Pyrenomycetes. If they occur, they would seem to be of an unusual character and difficult to recognize or else are evanescent, disappearing before the asci are mature. ASCOSPORES. The ascospores furnish one of the most marked characters for the separation of the genus into sections (Plate XVII). In section 1 they are more or less cylindric and sometimes curved. In section 2 they are more or less elliptic, being broadest in EndotMa para- sitica and narrowest in E. fluens and E. longirostris. The greatest variation in size and shape of ascospores occurs in E. fluens, as in- dicated by the measurements given in Table II. Anderson (1) , Clin- ton (18), and Heald (39) describe and figure the ascospores of E. parasitica as very obtuse and constricted at the septum. The writers have but rarely seen spores of this form. This may perhaps be due in part to different methods of treatment or to the age and condition of the material. Most of the ascospores studied by the writers have been mounted in the fluid medium described on page 30. Fresh specimens have also been studied in water mounts, but with the same general result. The writers are of the opinion, therefore, that the figures of the authors cited above do not represent the most common and characteristic form of ascospores of this species. (Com- pare Plate XVII, figs. 7 to 15.) 43737°— Bull. 380—17 3 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE, 0 §5 IS CO rl OO |"l-^5 O -FH is COp-frH ^ 10 CO ^(^2 ^° II ^ rHIN 00 II O s 0 OO LO OO O5 CO ^ SS coot- s-|- - 0 CO O5 || >C . si SIS a ssg §r 00 co COCO^C.0^ -5 "5 U5t>. ^S2S S2 asl * 2«s §2 r4 -r 33 d : : i-H OO O rH SS 0505 00 iC CO O s2 CO : : : <*« ; """ "1 s oo^co "2 d JZj 82S3&S5 II! Ills 100 COJ> || 25 I CO Sphaeria radicalis, Fries's herbarium ... . ... 1 oc 0 C : : : : o : Endothia tropicalis: 1 Cpvlrm ^o » E. parasitica: On Castanea sp., Santun- ying, China 215 On Castanea dentata— From Pantanelli l 165 Gordonsville, Va 173 OHAntnn MH 171 " i £. li i . I .. j 1 | ! >> : c I : •c | jf ^f ^ «' II j|f IS I! jj j IS w w 36 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. PHYSIOLOGY. CULTURAL STUDIES.1 During the past three years the writers have had under observation more than 4,000 cultures of the several species of Endothia on more than a dozen artificial media, as well as on sterilized twigs of many kinds. Throughout this work the writers have been impressed with the uniformity of the behavior of the organism in culture and the certainty with which the various species could be distinguished on any of the media used. Cultures of Endothia parasitwa, ior instance, from specimens sent from China or British Columbia were absolutely indistinguishable from cultures made on the same medium from local material. Transfers made from stock cultures which had been kept on artifi- cial media for two years were identical with transfers from freshly collected material. The same remarkable constancy held for the other species. Cultures from material collected in different localities or from different hosts were identical, not only in appearance but, so far as the writers were able to determine, in temperature and moisture relations also. As previously noted, this is in marked contrast to the senior writer's experience with the species of Glomerella and it is believed differs from the experience of many investigators of fungi. No less striking is the certainty with which the several species may be distinguished on any medium tried. Endothia parasitica^ E. tropicalis, and E. fluens and its variety mississippiensis are very closely related morphologically. Moreover all except E. parasitica have, as near as could be determined, much the same relation to their hosts. Yet each species has distinctly and readily recognized charac- ters on culture media. It should not be imagined, however, that the differences are recognizable at once as clearly distinctive characters. The differences at first glance might readily be considered fluctuating variations. But the fact that the characters remain constant through hundreds of generations and have never varied toward one another makes them worthy of recognition as specific characters. In a previous paper (77) the writers described their results with cultures of Endothia parasitica, E. fluens, E. fluens mississippiensis, and E. gyrosa on a number of culture media. At that time the work of other investigators was reviewed and the methods of preparing the various culture media and making the cultures described. Since the publication of that paper, However, cultures of two more species, E. tropicalis and E. singularis, have been secured and about 2,000 additional cultures of the various species made. In addition to the culture media mentioned in the previous paper (77, p. 10), the writers 1 The cultures described were all grown at ordinary laboratory temperatures in the winter, about 20° to 24° C. ENDOTHIA PARASITICA AND RELATED SPECIES. 37 have grown the organisms on sterile twigs of many species and on liquid media. As stated above, the various species of Endothia are distinguish- able on any medium tested. White corn meal in flasks has, however, been most used by the writers in identification work and for keeping stock cultures. All the species grow readily on this medium and may be determined with certainty within 10 days under ordinary con- ditions of growth. In addition, the medium is cheap, easily pre- pared, and does not dry out so quickly as agar media in tubes, so cultures may be kept alive much longer without transfers. Almost equally good for purposes of identification are rice and oatmeal in flasks, corn-meal agar, and potato agar. The distinguishing characteristics of the various species in culture have been described rather fully in the previous publication and may be briefly summarized, as follows: CULTURES ON CORN-MEAL AGAR (UNSLANTED TUBES). Corn-meal agar proved the best agar medium for the production of pycnospores and showed constant differences in the cultural characters of the various species. The most characteristic differences appeared in cultures from six to eight weeks old on unslanted tubes. (See PL XXI, figs. 2 to 7.) Endothia gyrosa at this age showed a rather abundant, felty white myce- lium, flecked with capucine buff, but there were no pycnidia. In older cul- tures small pycnospore threads were sometimes produced. Usually before the cultures were 10 days old the medium was changed to a delicate lavender just below the mycelium, and below this to a light olive green. A few days later the lavender disappeared and the green deepened to olive green. Endothia singularis grew more slowly than any other species. Within three weeks, however, the mycelium covered the entire surface. It was smoother than E. gyrosa and nearly white, with raw umber spots where the mycelium touched the glass. The medium was changed to a light hellebore green one-half inch below the top. Endothia fluens, as pointed out in the previous paper, produced an abundant deep-chrome mycelium, with usually one or two rather small pycnidial pus- tules. Endothia fluens mississippiensis produced a scant surface growth of my- celium, between cadmium yellow and raw sienna in color. The upper one-half centimeter of the agar became reddish orange. The pycnidial pustules were more numerous than those of E. fluens, but smaller and more scattered than those of E. parasitica. Endothia longirostris at the end of six weeks had a scant, webby, orange, aerial mycelium growing against the glass. Mycelium on the surface of the medium was very scant, orange to cadmium yellow in color, with scattered tiny xanthine orange to orange spore masses. The color of the agar changed to medal bronze just beneath the mycelium, shading into orange citrine below. Endothia tropicalis at the end of six weeks showed a thinly felted mycelium, white to capucine orange, with numerous small, scattered pycnidial pustules. The ring of mycelium against the glass was light orange yellow, as contrasted with white in E. parasitica. 38 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. Endothia parasitica gave a scanty white growth of surface mycelium, with several prominent pycnidial pustules clustered near the center and of a slightly darker shade than the " raw sienna " of Ridgway.1 CULTURES ON POTATO AGAR (SLANTED TUBES). Potato agar was used by the Andersons (3) to distinguish Endo- thia parasitica from E. ftuens. The writers have used it extensively and found it a very useful medium for distinguishing the species. As stated in the previous paper (77, p. 11), however, unless this medium was very carefully prepared it varied greatly in acidity and probably in other respects, with resultant variations in the behavior of the organisms. Spore production was not so abundant on this medium as on many others. The preparation of this and other media is described in the paper cited. Endothia gyrosa. — This species developed rather slowly, producing a fairly abundant aerial growth, which was felty rather than fluffy. The color was white, necked with capucine buff, and no spore masses were produced. Endothia singularis. — This species grew even more slowly than E. gyrosa. On cultures made from conidia, growth was hardly perceptible at the end of three days. Mycelial cultures at the end of one week showed less growth than E. gyrosa, but did not differ greatly from it in either color or texture. At the end of one month the mycelium was slightly more fluffy and decidedly less in amount than that of E. gyrosa. Most of the surface was a very light buff color, with sometimes a few spots of capucine orange to English red. Endothia fluens. — Pycnospore streak cultures of this species varied some- what as to the amount and time of appearance of color, probably due to the variations in the acidity of the medium referred to above. Many tubes showed an orange color in one week, while others produced no orange what- ever. In no case did cultures of E. fluens produce the " brassy " metallic sur- face appearance so characteristic of E. parasitica. Pycnidia were few and more scattered than in E. parasitica and did not begin to appear until the third or fourth week. A slight amount of warbler-green color sometimes appeared in the medium at this age, but never so conspicuously as in E. parasitica. Endothia flucns missis sippicnsis. — This produced a less fluffy aerial mycelium along the spore streak than E. parasitica. After five or six days the fungus showed an orange color by transmitted light, and was indistinguishable in this respect from E. parasitica. The character of the surface was somewhat different, however, and by reflected light appeared vanthine orange. When two weeks old this form differed still more markedly from E. parasitica in color, being grenadine red by transmitted light and showing no spore masses. E. longirostris. — At the end of one week this produced a white, fluffy growth scattered in small patches over the surface of +he medium. This later became rather close in texture, especially near the base of the agar slant. No spores were produced on this medium. Endothia tropicalis. — At the end of one week this showed less growth than E. fluens, covering about a third 6f the surface of the medium, while the other covered nearly the entire surface. The mycelium was closely matted and a very pale buff (paler than any in Ridgway). At the end of one month 1 In the descriptions of cultures comparisons were necessarily made with cultures in flasks or tubes. This of course made comparison more difficult and somewhat less accurate than if the material had been removed from the container. ENDOTHJA PARASITICA AND RELATED SPECIES. 39 E. tropicalis covered the entire surface with a thin layer of surface mycelium, considerably darker in color than when one week old. Endothia parasitica. — At the end of three or four days at room temperature this showed a short, fluffy, white, aerial growth along the streak. The surface of the mycelium was orange by transmitted light, while by reflected light it was between raw sienna and antique brown at the sides. Within six days the mycelium, especially at the base of the agar slant, took on a peculiar metallic " brassy " appearance, due apparently in part to the character of the mycelium and in part to the minute water drops scattered over the surface. This portion of the culture was light orange yellow by reflected light and orange by transmitted light. This metallic appearance has been found to be the most constant and reliable distinguishing character of E. parasitica on potato agar. In 12 to 14 days small pycnidial pustules appeared in the upper portion of the tubes, and the agar just below the mycelium became warbler-green, changing later to olive green. CULTURES ON CORN MEAL (IN 100 C. C. ERLENMEYER FLASKS). Endothia gyrosa. — Mycelial cultures one week old showed a growth of rather compact mycelium covering nearly one-half the surface of the medium. The mycelium was ochraceous buff near the point of inoculation, shading into white at the margin. There was no discoloration of the medium and no spore masses were seen. Cultures of the same kind one month old showed an abundant, rather thick growth, having the surface mostly covered with somewhat irregular tubercular masses, suggesting immature pycnidial stromata similar to those found in E. radicalis, but smaller and producing no spores. The surface of the culture was capucine buff, that of the tubercles honey yellow to Isabella. The dark color was apparently due in part to numerous superficial water drops. A por- tion of the medium wras changed to perilla purple. Endothia singularis. — Mycelial cultures one week old covered only one-third of the surface. The growth was mostly white and fluffy, with ochraceous buff near the center. At the end of one month the growth had entirely covered the surface. The mycelium varied in color from cadmium orange to capucine buff, the color being distributed over the surface in patches. The corn meal was changed to perilla purple near the center. No spores were produced. E. singularis wras readily distinguishable from E. gyrosa, wrhich it resembled more closely in culture than any of the other species, by the rate of growth and the color and nature of the surface of the mycelium. E. singularis grew more slowly than E. gyrosa, was rather brighter in color (cadmium orange), and the surface of the mycelium was decidedly more even, lacking the tubercular masses characteristic of E. gyrosa. Endothia fluens. — Cultures at the age of one week showed a growth of loose, fluffy mycelium covering one-half of the surface of the medium. The mycelium was deep chrome to light orange yellow at the point of inoculation, passing through perilla purple and light pinkish lilac and fading into white at the margin. Occasionally the medium was changed to perilla purple near the center. No spores were present. Cultures one month old showed a compact growth, with a nearly smooth surface. The color ranged from light cadmium to empire yellow. The whole mass of the medium was perilla purple. Spore masses were rarely present at this stage, but shortly afterwards a few large erumpent stromata were formed, which extruded spores in thick masses. 40 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. Endotliia fluens mississippiensis. — Cultures one week old showed an orange- chrome growth a little more than half covering the surface of the medium. The superficial growth was very similar to that of E. parasitica. There was no discoloration of the medium and no spore masses were found. The same organism one month old produced a growth with a compact, rather uniform surface, the superficial portion having a coarse, matted, webby appear- ance, which was most noticeable about the margin. The color of the mycelium was cadmium orange to xanthine orange, while that of the medium was un- changed. Spore masses were much more numerous than in E. fluens, but smaller and less numerous though very similar to those of E. parasitica. E. longirostris. — Cultures one week old covered about one-third of the sur- face of the medium. The mycelium was short, fluffy, white, with only a tiny spot of cadmium orange near the point (ft inoculation. At the end of six weeks the entire surface was covered with a compact growth rather uniform in tex- ture, cadmium orange to xanthine orange in color. The surface was irregularly ridged, giving it a wrinkled appearance, with tiny mars orange spore masses irregularly scattered over the surface. This species closely resembles E. fluens mississippiensis on this medium, being distinguished from that variety by the smaller and much less numerous spore masses. The medium is changed to amber brown just below the mycelium, shading into mars yellow in the lower portions. Endothia tropicalis. — At the end of one week this showed less growth than either E. parasitica or E. fluens, covering about a third of the surface. The mycelium was matted close to the surface and was a very pale buff (paler than any of the buffs shown in Ridgway). No pycnidia were present. At the end of one month's growth the surface was entirely covered with a closely felted mycelium and small, numerous, thickly scattered spore masses, more closely resembling those of Endothia parasitica than any other species. The mycelium was orange buff to apricot orange, and orange chrome against the glass. The color of the medium was unchanged. Endothia parasitica. — In cultures one week old the growth on corn meal covered about one-half of the surface of the medium. The outer margin was pure white, the remainder buff yellow below, with a superficial white growth above. A few small pustules with spore masses occurred near the point of inoculation. The medium was uncolored. Cultures one month old showed a compact growth, nearly smooth on the surface. The superficial mycelium was pale orange yellow. The pale yellow- ocher spore masses were minute, very numerous, and nearly covered the sur- face. The medium was slightly greenish about the sides of the flask just beneath the mycelium. DISTINGUISHING CHARACTERS OF THE VARIOUS SPECIES ON CORN MEAL IN FLASKS. The color reactions of the various species on corn meal are very striking. Endothia fluens (PI. XXI, fig. 1&), as noted above, changes the whole mass of the medium to perilla purple in less than a month. E. gyrosa and E. singularis also produce this color change, but somewhat more slowly. E*; fluens mississippiensis, E. tropicalis. and E. parasitica, on the other hand, in hundreds of cultures have wholly failed to produce any purple color. This furnishes an easy and reliable method of distinguishing E. parasitica from E. fluens Bui. 380, U. S. Dept. of Agriculture. PLATE XVII. \ M I - 6 « 8 10 11 12 PHOTOMICROGRAPHS OF PYCNOSPORES AND ASCOSPORES OF ENDOTHIA. FIGS. 1 TO 6.— PYCNOSPORES: 1, ENDOTHIA GYROSA; 2, E. SINGULARIS; 3, E. FLUENS; 4, E. LONGIROSTRIS; 5, E. PARASITICA (AMERICAN); 6, E. PARASITICA (CHINESE), FIGS. 7 TO 1 5.— ASCOSPORES: 7, E. GYROSA; 8, E. SINGULARIS; 9, SPHAERIA RADICALIS, FROM SCHWEINITZ'S SPECIMEN IN FRIES'S HERBARIUM; 10, ENDOTHIA PSEUDORAD- ICALIS; 11, E. FLUENS; 12, E. FLUENS MISSISSIPPIENSIS; 13, E. LONGIROSTRIS; 14, E. TROPiCALiS; 15, E. PARASITICA. Bui. 380, U. S. Dept. of Agriculture. PLATE XVIII. ENDOTHIA PARASITICA ON PLATE CULTURES OF CORN-MEAL AQAR 4 WEEKS OLD. THE UPPER PLATE WAS KEPT IN TOTAL DARKNESS: THE LOWER PLATE IN THE DIRECT LIGHT OF A NORTH WINDOW. Bui. 380, U. S. Dept. of Agriculture. PLATE XIX. ENDOTHIA SPECIES ON WHITE CORN MEAL (10 GRAMS OF CORN MEAL TO 20 C. C. OF WATER). CULTURES 2 MONTHS OLD. FIG. 1.— ENDOTHIA GYROSA-, FIG. 2.— E. SINGULARIS; FIG 3.— E. FLUENS; FIG. 4.— E. FLUENS MISSISSIPPIENSIS. Bui. 380, U. S. Dept. of Agriculture. PLATE XX. ENDOTHIA SPECIES ON WHITE CORN MEAL (10 GRAMS OF CORN MEAL TO 20 C. C. OF WATER). CULTURES 2 MONTHS OLD. FIG. 1.— ENDOTHIA TROPICALIS-, FIG. 2.— E. PARASITICA; FIG. 3.— E. LONGIROSTRIS. Bui, 380, U. S, Dept, of Agriculture, PLATE XXI. **» • »'>*•' '' CULTURES OF ENDOTHIA SPECIES FIG. I.— a, Corn meal after i month's growth of Endothia parasitioa; b, corn meal after i month's growth of E, fluens. Typical cultures on upright tubes of corn-ineal agar 6 weeks old. FIG. 2. — E. gyro&i. FIG. 3.— E. singularis. FIG. A,.— E.jluens. FIG. 5.— E. fluins mississippicnais. Fio. 6— E. tropically. FIG. 7. — E. parasitica. ENDOTHIA PARASITICA AND BELATED SPECIES. 41 (PL XXI, fig. 1) in field work when fructifications of the species are wanting or doubtful. Aside from the differences in color, the most conspicuous and important characteristic of these fungi in corn-meal cultures is found in the fructification. Clinton (18, pi. 26) has already men- tioned and illustrated similar differences in cultures of these organ- isms on agar in Petri dishes. In Endothia parasitica the pycnidia and spore masses are small, numerous, thickly scattered, and em- bedded in the mycelium. E. fluens, on the other hand, forms few, large, erumpent stromata, with spores extruding in thick, elongated masses. E. tropicalis closely resembles E. parasitica in number, size, and arrangement of pycnidia and spore masses, but differs in color of mycelium. E. ftuens mississippiensis appears somewhat inter- mediate between E. parasitica and E. fluens in regard to the character and abundance of the pycnidia and in color of the growth. These peculiarities have been very uniform and constant in all the cultures on this medium and if they could be coordinated writh regular mor- phological differences in nature would justify the separation of this form as a species. (See Pis. XIX and XX.) CULTURES ON LIQUID MEDIA (IN 100 C. C. FLASKS). Some difficulty was experienced at first in growing the species of Endothia satisfactorily on a liquid medium. Abundant growth was obtained on a medium suggested by Dr. Mel. T. Cook. This is a modification of the liquid medium No. II as given by him (19). Cook's liquid medium, No. II, is prepared as follows : Into 500 c. c. of distilled water put 15 grams of glucose and 20 grams of peptone steamed at 100° C. for three-fourths hour; into another 500 c. c. of distilled water put 0.25 gram of dipotassium phosphate and 0.25 gram of magnesium sulphate, steamed for 20 minutes; filter both 500 c. c. into same receptacle, steam 10 minutes, put into flasks, about 30 c. c. in each flask, and autoclave. All species grew readily on this medium, Endothia parasitica even producing pycnospores. At the end of one month's growth the sev- eral species were readily distinglished on this medium and may be briefly described as follows: Endothia gyrosa. — Growth scanty; did not form a continuous mat, but re- mained in small bunches, giving an almost flocculent appearance. The mycelium appeared white when removed from the culture solution, but the solution itself was honey yellow. Endothia singularis. — Growth even less abundant than E. gyrosa; formed small brown knots against the glass. Mycelium buff, and the medium was changed to honey yellow. Endothia fluens. — Growth somewhat more abundant and less closely matted than E. parasitica, entirely submerged; mycelium white; liquid unchanged in color. 42 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. Endothia fluens mississippiensis. — Growth slightly less abundant than in E. parasitica; submerged except at the very edges ; much lighter in color, being reddish brown. Endothia tropicalis. — This differed markedly from either E. parasitica or E. fluens. The mycelium formed a thin felt over the surface, white to salmon orange in color, with no change in the medium. Endothia parasitica. — Mycelial growth very abundant, closely matted, chiefly submerged, but slightly arborescent in one or two small areas, which remained above the surface. Color, dark greenish brown. CULTURES ON STERILIZED TWIGS (IN TUBES). Early in this work it was notec^ that all the species of Endothia grew readily on sterilized chestnut twigs in test tubes. Later, tests were made with twigs from a number of common, woody plants. Twigs of Acer saccharum, Alnus rugosa, Betula papyri/era and B. lenfia, Carpinus caroliniana, Cornus florida, Fagus grancfifolia, Fraxinus americana, Ostrya virginiana, Populus grandidentata, Prunus serotina, Rhus glcibra, Tilia americana, and Tsuga canadensis were collected in New York State early in June, placed in test tubes with a few cubic centimeters of distilled water and sterilized in an autoclave. All the species of Endothia were tested, and all grew on every species of twig except Tsuga. The difficulty of completely de- scribing this series may readily be seen from the fact that each species of Endothia had a different appearance on every kind of wood. In general it may be stated that Endothia gyrosa and E. singularis grew more slowly than the other species and produced no spores, while all the other species produced spores on most hosts. The mycelium of E. parasitica was usually white,. especially on the bark. E. gyrosa and E. singularis produced various shades of buff, while E. fluens, E. fluens mississippiensis, and E. tropicalis developed a much more brightly colored mycelium, usually showing yellow or orange shades. MOISTURE RELATIONS. In an earlier paper (77, p. 7) the writers reported tests with Endothia fluens and E. parasitica on media containing various per- centages of water. It was observed that pycnospore production began earliest and was most abundant on the media containing the least moisture. Aside from this the writers have thus far been unable to make definite tests as to the moisture relations of these fungi. However, incidental observations in connection with the light tests (p. 43) and temperature tests (p. 45), as well as results of field experiments, particularly those at Woodstock, N. Y., make it apparent that the amount of available moisture is a very important factor in the fructification of the fungus. ENDOTHIA PAEASITICA AND RELATED SPECIES. 43 LIGHT RELATIONS. The relation of light to pycnospore production in Endothia para- sitica was first discussed by Anderson (1, p. 20). He says — When plate cultures are grown in total darkness on chestnut-bark agar, no pycnidia are developed, while on plates made at the same time and grown in the light, the usual rings of pycnidia appear (fig. 57). Experiments were also tried in which the plate was left in darkness until about half covered with mycelium and then brought into the light. Circles of pycnidia were developed, beginning with the ring which marked the outermost limit of the colony when removed from the dark chamber. The concentric rings which always appear on agar cultures are due to the alternation of night and day. Later, in a bulletin by Anderson and Rankin (6, p. 592), the same results are attributed to D. C. Babcock. Up to the time the above-mentioned work was published the writers had grown about 3,000 cultures of the several species of Endothia on various media in flasks and tubes. Practically all of these cultures had been kept in dark cases and EndotMa parasitica had produced pycnidia abundantly on most of the media used. It seemed desirable, therefore, to determine whether wholly different light relations existed when the fungus was grown on plates. The following series of tests was accordingly made, using E. parasitica only. LIGHT TESTS OF CULTURES ON PLATES. In experimenting with plate cultures in order to check up the results reported by Anderson and Rankin (6, p. 592) it was noted that there was great variation in the rate at which the cultures dried out. There was considerable variation in this respect in dif- ferent plates kept side by side, apparently due to differences in the Petri dishes, and a marked difference between cultures kept in light and those kept in darkness. Since a causal relation between lack of moisture and abundant spore production had already been shown, it seemed probable that this might influence the results of the light tests in plate cultures. In fact, in a few cases the cultures kept in the light did produce spores earlier than those kept in dark- ness. Accordingly, in order to eliminate at least in part this fact which seemed to obscure the possible effect of light, a method was sought of equalizing the loss of moisture. In the following series half the plates were placed under a plain bell jar and the other half under a bell jar of equal size but darkened by being covered inside and out with heavy black paper, such as is used to wrap photographic plates. The two bell jars were then set side by side in front of a north window. By this means the conditions were made much more uniform as to temperature and moisture. There was still a slight difference in the rate of drying and undoubtedly at times a difference 44 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. in the temperature of the light and dark plates, but probably not sufficient to interfere seriously with the experiments. Series 1. On corn-meal agar plates under bell jars. — In nine days there was no distinguishable difference between the plates in light and darkness, a few spore masses occurring near the middle of each. In 18 days most of the light plates showed a central ring of spore masses and a zone of scattered spore masses near the edge. The dark plates showed a few small spore masses near the center, and scat- tered about the outer portion were the small masses of mycelium which usually constitute the early stages of pycnidial formation. In 30 days the number of spore dnasses had increased somewhat in both sets of plates, but more in the darkened plates, so that the number of spore masses was about equal in all the plates. The two sets of plates were fairly uniform as to the arrangement of the spore masses. Plate XVIII shows a typical example. Series 2. On chestnut-twig agar pieties under bell jars. — After nine days the cultures in light and darkness were alike. No spores had yet appeared in either set. In 30 days there were a few spore masses on nearly all of the plates, there being no difference between those in light and those in darkness either in number or distribution. Series 3. On corn-meal agar and chestnut-twig agar under bell jars. — In this test the plates were piled alternately, first a corn-meal and then a chestnut-twig agar plate, so that the two media would be under conditions as nearly identical as possible. The plates were inoculated as before and left untouched for 18 days and after that were examined daily. After 18 days all the corn-meal plates showed spore masses in practically equal numbers, while the chestnut-twig agar plates showed no spore masses whatever. There was no ap- parent difference in the growth on either medium between the plates in light and those in darkness. At the end of 25 days the cultures on chestnut-twig agar plates showed numerous small masses of mycelium, indicating the forma- tion of pycnidia. No difference was perceptible between the dark and light plates. In 28 days, from 100 to 150 of these pycnidia in each plate were extruding spore masses. The light plates showed in general a larger mass of spores than the dark plates, but this was not marked, cer- tainly no greater than was accounted for by the unavoidable dif- ference in radiation and the consequent difference in moisture. This difference in the moisture of the medium was clearly shown each morning by the greater amount of moisture condensed on the covers of the darkened Petri dishes. At this time (after 28 days) four corn-meal agar plates which had been wrapped in four layers of heavy black photographic paper and ENDOTHIA PARASITIC A AND RELATED SPECIES. 45 placed on a window sill were opened and examined. In spite of the cold weather prevailing during this test and the consequent low tem- perature of the room at night, these plates contained an average of nearly 200 well-developed spore masses. At the end of 35 days the chestnut-twig agar plates which had been kept in the light showed an average of 160 spore masses, while those kept in darkness showed an average of 130 spore pustules, a comparatively small difference in favor of the light plates. There was, however, a wide difference between the various plates in each series, and it was impossible in most cases to distinguish cultures grown in the light from those grown in darkness either by the num- ber, size, or arrangement of the pycnidia and spore masses. From these experiments it is evident that pycnidia are produced abundantly in total darkness on chestnut-twig agar as well as on other favorable media. There is no perceptible difference in the amount of spore production or in the arrangement of pycnidia be- tween cultures kept in total darkness and those kept in the light during the day if the temperature and evaporation remain the same in both. Continued observation of numerous cultures grown both in daylight and in darkness has convinced the writers that light has no perceptible effect on mycelial growth either in amount, nature, or color production. It seems evident, therefore, that light is a neg- ligible factor in the growth and fructification of these fungi. TEMPERATURE RELATIONS. In an earlier paper (77, p. 9) the writers published the results of three series of tests made to determine the temperature relations of three species of Endothia. Since the publication of that paper cul- tures of other species and additional material of some of the species from widely separated localities have been secured. Four series of temperature tests including this new material were made on solid media. TESTS ON SOLID MEDIA. In these tests cultures of Endothia gyrosa, E. singularis, E. fluens, E. ftuens mississippiensis, and E. parasitica were tried on corn-meal agar in slanted tubes, oatmeal in flasks, and potato agar in slanted tubes. The cultures tested were from specimens chosen from the extremes of the known ranges of the fungi and from their different hosts. No difference could be detected in the various cultures of the same species, even in those from widely separated localities and from different hosts. Cultures appeared to have the same temperature relations whether made from spores or mycelium. The results may be briefly summarized as follows: At 41° and 39° C. there was no growth in any species. Cultures removed from the incubator at the end of 11 days and kept at room temperature showed no growth. 46 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. At 35° C., Endothia gyrosa, E. singularis, and E. parasitica showed a slight development within 2 days, but at the end of 11 days it was still slight and abnormal in appearance. E. fluens and E. fluens mississippiensis showed no growth at this temperature. At 31° C., Endothia gyrosa, E. singularis, and E. parasitica appeared about the same as at room temperature for the first four days. At the end of six days these species showed somewhat less growth than at room temperature, while at the end of two weeks the growth was less in extent and markedly less freshly colored than that at room temperature. E. fluens and E. fluens mississippiensis showed somewhat less growth than at room temperature even in 4 days, and markedly less at the end of 2 weeks. At room temperature (which at this time varied from 20° to 24° C.) the growth was much as described in the previous paper. Within 11 days growth was practically complete and in 14 days there was abundant spore production in Endothia parasitica. At 18° and 16° C., all species showed considerably less growth than at room temperature, but there seems to be little difference in the comparative growth of the various species at these temperatures. At 13° the growth was decidedly less than at 16° C. but was fairly normal in appearance in all the species except that Endothia fluens mississippiensis failed to produce the characteristic color at this temperature. At 9° C. there was a very slight growth in all species. At 7°, 5°, and 2° C. there was no growth whatever. Cultures removed to room temperature at the end of 11 days developed normally and at about the same rate as in newly made cultures. These additional tests seemed to confirm the results already pub- lished (77, p. 27) ; that is, growth was best in all species at ordinary room temperature, about 20° to 24° C. The minimum temperature for all was about 9°, and all failed to grow at 7° C. The maximum temperature for Endothia gyrosa, E. singularis, and E. parasitica appeared to be about 35°, while the maximum for E. fluens and its variety E. fluens mississippiensis was apparently about 32° C. At all the temperatures tried E. singularis grew much more slowly than any of the other species. It was noted that cultures kept at 7°, 5°, and 2° C. showed no growth, but when removed to room temperature developed normally, while cultures kept at 41° and 39° C. failed to grow when removed to room temperature. This seemed to indicate that the fungi are more susceptible to heat than to cold, and such is perhaps the case. There was, however, the additional factor of moisture involved, for while the agar of the cultures kept at 7° and lower was in apparently the same condition at the end of 11 days as when first inoculated, the agar of the cultures kept at 41° to 39° C. was considerably dried. This raised the question as to whether the drying out of the agar had not affected the growth of the fungi in those cultures kept above room temperature as much as the higher temperatures themselves. The same idea was suggested by the- fact that several of the species grew for a few days at 31° C. as well as they did at room temperature, and then fell behind. It seemed possible that this falling off in the ENDOTHIA PARASITICA AND BELATED SPECIES. 47 rate of growth might be due, at least partly, to more rapid drying of the agar at 31° C., or possibly to the more rapid development of some toxin, as was suggested by Balls (7) to explain a similar observation on the "soreshin" fungus. These observations threw doubt upon the accuracy of the writers' previous conclusions, and made it seem possible that the optimum temperature of the species of Endothia might be well above room temperature. This could onlv be determined accurately by some method which would control tem- perature without altering the supply of moisture. Some months after the above tests were concluded it was discovered that the various species of Endothia would grow readily on several liquid media. Consequently, several series of tests on liquid media were run parallel to those described above, except that the tests were continued for only four days. Experiment showed that at the higher temperatures the medium became considerably reduced by evaporation if left for a longer period. TESTS ON LIQUID MEDIA. In the series of tests on liquid media, all the species of which cul- tures had been obtained were grown on Cook's medium (see p. 41) both in tubes and in flasks, using ten tubes and six flasks at each temperature. The cultures of Endothia gyrosa and E. singularis were made with bits of mycelium from pure cultures. The other species were grown from conidia and the cultures were kept for two days at room temperature, in order to allow the conidia to germinate before being placed in the temperatures to be tested. The following temperatures were used for making the tests: 40°, 37.5°, 35°, 29°, and 27°, and room temperature which was fairly constant at about 22°, 17°, 12°, 9°, 7°, 3°, and 2° C. There was some variation in the temperature of the incubators and refrigerators used, but in most cases they did not vary more than 1 degree above or below the temperature indicated. At 40° there were occasional traces of growth, especially in Endothia parasitica, but- this may have occurred when the incubator dropped to 39° C. There is no regular and continued growth at this temperature. At 37.5° C. there was perceptible growth in all the species. This is in striking contrast to the results on solid media, as no species grew at a temperature above 35° C. on solid media. At 35° C. Endothia parasitica showed practically the same amount of growth as at 27° and 29° C. for the first three days, but fell behind after that. E. fluens showed less growth at 35° than at the lower temperatures. These two species were the only ones tested at 35° C. At 27° and 29° C. growth was markedly more abundant than at 37.5°, and in most of the species was more abundant than at room temperature. In Endothia gyrosa and E. fluent mississippiensis the 48 BULLETIN 380, U. S. DEPAETMENT OF AGRICULTUBE. growth at 27° C. was apparently equal to that at room temperature. At 22° C. (room temperature) all species developed much more rap- idly than at the lower temperatures. At 17°, 12°, and 9° C. there was progressively less and less growth. At 7° C. and lower there was no growth whatever. While these tests are not wholly satisfactory and must be regarded only as approximations, they are of some interest. Below 7° C. there is no growth in any species. It is evident that there is a considerable range of temperature, from below 20° to well above 30° C., within which the species of En- dothia grow readily. Within tkis range there may be a definite optimum for each species, but this has not yet been determined. For Endothia parasitica the optimum appears to be at 27° C. or above, and the same may be true of the other species. At 40° C. or above no growth occurs. There is considerable evi- dence, however, that Endothia fluens is less resistant to the higher temperatures than either E. parasitica or E. gyrosa. After several of the tests the flasks were kept at room temperature for some days. It was found that all developed normally except those which had been kept at 40° and 37.5° C. These developed more slowly than those which had been kept at lower temperatures. It was particu- larly noticeable also that E. parasitica and E. gyrosa developed prac- tically as well after being kept at 40° as at 37.5° C., wrhile cultures of E. fluens which had been in 37.5° developed fairly well; but if kept at 40° for three days they entirely failed to develop. DISTRIBUTION OF THE SPECIES OF ENDOTHIA. During the past two years the writers have studied over 600 speci- mens of Endothia from various parts of the world. The greater number of these specimens have naturally come from the United States. The maps (figs. 1-4) show the known ranges of the various species in this country. Each dot on a map represents a locality from which the species has been collected. Frequently, of course, many specimens have come from a single locality ; hence the number of dots by no means represents the number of collections. In the case of Endothia parasitica, the dark portion represents the area over which the blight is practically continuous; that is, practically all the stands of chestnut are either diseased or dead. The dots represent known isolated infections and the solid line marks the botanical limit of the chestnut. Endothia gyrosa is known only from the United States, but has a range in this country wider than that of any other species. As shown in figure 1, it has been found as far north as central Michigan, east to Connecticut, on the Pacific coast near San Francisco, and on ENDOTHIA PAKASITICA AND RELATED SPECIES. 49 the Gulf of Mexico. There is, however, a very great difference in the abundance of this species at different points. In the southeastern United States — that is, the region south of central Indiana and southern Virginia and east of central Arkansas and Louisiana — this species occurs in great abundance wherever its hosts are found. Broken branch stubs and exposed roots of Liquidambar, Fagus, and Quercus are covered with fructifications of this fungus. This is especially true of roots exposed by erosion or excavation which have suffered mechanical injury through the tramping of men or cattle. Farther north in Maryland, New Jersey, and Connecticut only an occasional specimen is found. Three days' search in southern Con- FIG. 1. — Outline map of the United States, showing the distribution of Endothia gyrosa. necticut, for example, yielded only two specimens, both on Liquidam- bar, showing pycnidia only. Endothia singularis is known at present only on oaks in the dry foothill regions of Colorado and New Mexico. Bethel, in a letter, states that it is very abundant in certain localities in Colorado. Endothia fluens has long been known to occur in both Europe and America. Recently, through the kindness of Dr. Y. Kozai, director of the Central Agricultural Experiment Station, Nishigahara, Tokio, Japan, the writers received four specimens of fungi on chestnut. One of these, collected by S. Tsuruta on October 14, 1914, in the Province of Totomi, was the pycnidial stage of an Endothia, which when cultured proved to be E. fluens. Ascospore material of this species has since been collected by Meyer at Nikko, Japan, on the bark of Pasania sp. 43737°— Bull. 380—17 4 50 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. Endothia fluens, while common to Europe, Asia, and America, has a much more limited range in the United States than E. gyrosa. It is fairly common on Castanea and Quercus from southern Pennsyl- vania and Ohio to northern Mississippi and Alabama. In south- eastern Pennsylvania it has been found so far only on roots of Quercus, and in northern Mississippi and Alabama only on Castanea dentata. EndotJiia fluens mississippiensis was first sent to the writers from Corinth, Miss., by Mr. T. E. Snyder, of the Bureau of Entomology, and has since been collected in only four other localities, three near the northeastern corner of Mississippi and one in central Kentucky. FIG. 2. — Outline map of the United .States, showing the distribution of EndotMa fluens. As both Endothia gyrosa and E. fluens were collected in this country nearly a century ago by Schweinitz, it seems altogether probable that they are indigenous species which may have already reached the limits of their natural ranges in this country. While the maps (figs. 1-4) do not give by any means every locality where Endothia is to be found and specimens are likely to be col- lected at many points outside the present known range, the writers feel justified in assuming that these maps represent the limits of the territory where Endothia gyrosa and E. fluens may commonly be found. This is especially trile in the eastern portion, where the field has been rather thoroughly worked. It is unlikely, for instance, that E. fluens occurs abundantly in southern Alabama and Georgia, where E. gyrosa was found so commonly. Southeastern Pennsyl- vania must be somewhere near the northern limit for E. fluens, for the writers' four collections in that region are the result of six days' ENDOTHIA PAKASITICA AND RELATED SPECIES. 51 search. At the northeastern limit of E. gyrosa, Clinton (15, p. 79) found only a single specimen after two years' search, and the writers have looked for it in all the other New England States without find- ing a single specimen. The report of E. gyrosa from Massachusetts by Hitchcock (42, p. 63) has already been shown to be a probable error in identification. FACTORS INFLUENCING DISTRIBUTION. HOST RELATIONS. Just what determines the present ranges of the species can not, of course, be positively decided, but some relation to certain external factors may be traced. Neither species has the same distribution as FIG. 3. — Outline map of the United States, showing the distribution of EndotJiia fluens mississippiensis and E. singularis. The dots indicate collections of E. fluens mississippi- ensis and crosses indicate collections of E. singularis. its hosts. Quercus and Fagus are both abundant farther north than EndotJiia gyrosa has yet been found, while Quercus is abundant north and south of the known range of E. fluens. It may be worthy of note, however, that E. gyrosa extends north as far as Liquidambar is found. Perhaps more significant is the relation of the range of E. fluens to that of the chestnut. As will be seen from a comparison of the maps (figs. 2-4) , E. fluens is not found abundantly at any point outside the natural range of the chestnut. Especially interesting is the fact that the southeastern limits of E. fluens and Castanea den- tata are practically coincident, for in this region EndotJiia fluens was found only on Castanea, never on Quercus. This suggests the possibility that Castanea may be the original and favorite host of EndotJiia fluens. 52 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. SOIL CONDITIONS. Greater opportunity for infection seems to be an important factor in the greater abundance of Endothia in the South. By far the most favorable places of infection, especially for EndotMa gyrosa, are bruised or broken but still living roots. Soil, cultural, and climatic conditions combine to make these many times more abundant in the Southern States than elsewhere. The more sandy and easily eroded soil, usually without turf, subject throughout the winter to the action of wind and rain, leaves innumerable oak roots exposed, which are readily injured by vehicles and the tramping of horses and cattle, leaving wounds suitable for the entrance of Endothia. In the FIG. 4. — Map of the United States, showing the distribution of Endothia, parasitica in December, 1915. The solid portion shows the area in which E. parasitica is generally present. The dots indicate scattered infections. The heavy line shows the limits of the range of Castanca dcntata. North, the more rocky soil, frequently covered with sod, protected through much of the winter by snow, makes exposed roots much less common, and the roots so exposed are rather less subject to mechani- cal injury. In the writer's experience the most favorable localities for collecting E. gyrosa are the unfenced public squares of Southern towns, where partial grading, erosion, and constant traffic have left hundreds of oak roots exposed, and the pastures of southwestern In- diana, where the roots of Fagus are often found injured by cattle. COMPETITION AMONG FUNGI. The writers' extensive field studies and observations have con- vinced them that competition among fungi must be considered as a EXDOTHIA PAKASITICA AND RELATED SPECIES. 53 factor in determining their distribution. As already stated, while EndotMa fluens occurs on Quercus, it has been found toward the southwestern limit of its range (northern Mississippi and Alabama) only on Castanea, and in Tennessee the writers have sixteen collec- tions of this species on Castanea and only three on Quercus. In this same region, E. gyrosa is everywhere abundant on Quercus. In numerous inoculations with E. gyrosa and E. -fluens on oak it has been found that E. gyrosa is more generally successful than E. fluens. Moreover, E. gyrosa occurs abundantly on Liquidambar and Fagus in this region, thus providing more numerous sources of infection for this species than for E. fluens. It seems highly probable, there- fore, that E. gyrosa, writh its greater affinity for oak and greater opportunity for infection, may occupy the available oak roots to the exclusion of E. fluens, even though climatic conditions are favor- able for the growth of the latter species. Castanea rarely serves as a host for E. gyrosa; consequently, on this host E. fluens meets with little competition and is very abundant. In the northeastern limit of its range, EndotMa fluens has been found only on oak roots. Whether it grows naturally on chestnut in this region can not well be determined, since practically all the chestnut trees here are dead or badly diseased with E. parasitica. E. gyrosa is rare in this region, but E. fluens here evidently comes into competition with Valsa frustum-coni (Schw.) Curtis, which is common on exposed roots of various species of Quercus. CLIMATE. Since none of the species of Endothia in America extends to the limits of its host species, climate probably has an important part in determining their present ranges. In this connection it is of interest to compare several life zone and climatic maps which have been published with the range maps of the various species of Endothia. The map entitled " Life zones of the United States," by C. Hart Merriam (50, pi. 14), is based largely on a study of animal life. Merriam deduces from his studies the conclusion that the northward distribution of animals and plants is determined by the total quantity of heat and their southern dis- tribution by the mean temperature of the hottest part of the year. The life zones which he outlines show, however, a striking relation with the known ranges of Endothia in America. With the exception of a single locality for Endothia gyrosa in Michigan, all the known localities for E. gyrosa and E. fluens fall within the Upper Austral and Lower Austral zones. All the known localities for E. fluens and all the region where E. gyrosa has been found abundantly fall within the humid divisions of these zones. The northeastern limits of the Upper Austral coincide very closely with those of E. gyrosa; its 54 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. limits in Pennsylvania include the northern localities known for E. fluens, while the southern limits of this zone coincide closely with the southern limit of E. fluent. The Livingstons (47) have published maps based on temperature summations and temperature efficiencies, as well as maps in which isoclimatic lines of temperature are combined with precipitation indices and evaporation indices for the mean frost-less season. While no very definite relations between these maps and the ranges of Endothia can be traced it is noteworthy that the localities where Endothia gyrosa is known to be abundant are all south of or near the 600 line of temperature efficiency, and only one collection of E. gyrosa has been made north of the 400 line. E. singularis, on the other hand, has thus far been found only north of the 400 line. Zon's map (86) of vegetal regions of the United States is based on periods of growth and rest. The regions where Endothia gyrosa and E. fluens are abundant are all south of the line which marks the northern limit of seven months' vegetation. In fact this coincides very closely with the northern limit of E. fluens, and no specimen of E. gyrosa showing ascospores has been found farther north. The relations pointed out above strongly suggest the possibility of some causal connection between climatic conditions and the present ranges of Endothia species, but just what factors may limit the spread of the species is not yet determined. The temperature tests recorded on pages 45 to 48 throw little light on this problem, for the maximum and minimum temperatures are about the same in the vari- ous species. Endothia fluens seems to be less resistant to the effects of high temperature (40° C.), but it is difficult to see that this fact alone has any direct bearing on the question of distribution. DISCOVERY OF ENDOTHIA PARASITICA IN CHINA. For eight years after its discovery in the New York Zoological Park in the summer of 1904, Endothia parasitica was known only from eastern North America, During this time two quite different opinions as to the origin of the fungus were advanced. Some in- vestigators maintained that E. parasitica was an indigenous fungus (15) ; others that it had been imported from some foreign coun- try, probably oriental (51, 52.) In the fall of 1912, however, pyc- nospore material was sent from Agassiz, B. C., by H. F. Giissow, Dominion Botanist of Canada. Cultures made from this material were identical with E. parasitica, and a series of inoculations on Castanea dentata produced typical cankers. Later, a large quantity of material collected at Agassiz by Dr. James R. Weir was received, which included a few ascospores. These proved to be typical E. parasitica. ENDOTHIA PARASITICA AND BELATED SPECIES. 55 A brief description of the identification of other specimens of E. parasitica from Agassiz is given by Faull and Graham (29). These writers report that in the material sent them in the summer of 1913 there were no perithecia, but that the pycospores were typical E. parasitica and the characteristic mycelial fans were present in the bark. Cultures of the fungus proved it to be identical with E. parasitica. They also state (p. 203) that the chestnuts grown at Agassiz " are of oriental, European, and American origin. The stock was purchased from nursery firms located in New Jersey, Ohio, and California. One of these at least ' was a heavy importer of oriental trees and shrubs '." They suggest that it " is significant that a connection with the Orient exists." In support of this view, the statement of Mr. Sharpe, who had charge of planting the nut orchard at Agassiz, may be given. Dr. Weir visited Mr. Sharpe at Salmon Arm, B. C., and Mr. Sharpe stated definitely to him that he would be willing to furnish affidavit to the effect that in the main or entirely the chestnut trees in the nut orchard were originally imported from the Orient; in fact, a part of the trees, according to Mr. Sharpe, undoubtedly came from Japan or China and were shipped to Agassiz in the original wrap- pings, which consisted of the peculiar mats and casings of those countries. In a letter accompanying the specimens from British Columbia Giissow states that " these trees may be regarded as absolutely iso- lated. There is no other chestnut tree anywhere round it for 500 miles and more." It seems highly probable therefore that E. para- sitica was carried to this locality on nursery stock, perhaps as sug- gested by Faull and Graham and by Weir by importation from the Orient. The following spring (1913) Mr. Frank N. Meyer, agricultural explorer, discovered this fungus in Chihli Province, China, under such conditions as could leave no doubt that it is indigenous there. The account of this discovery and its corroboration in this country was published by Fairchild (27), and also by the writers (76). As outlined by Fairchild (27), Meyer first found the diseased chestnuts near Santunying, a small town 1J days journey by cart from a railroad, northeast of Peking in Chihli Province, between Tsunhua- tcho and Yehol. A small specimen of diseased chestnut bark from this region was inclosed in a letter from Mr. Meyer which was received by Mr. Fair- child on June 28, 1913. From this specimen, which showed only pycnospores. cultures were obtained, which proved it to be true E. parasitica. On July 23 more Chinese specimens were received from the same locality, as well as from Scha Ho in the same Province. These included a large canker on a chestnut branch about 6 cm. in 56 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. diameter, which agreed in every respect with cankers produced on varieties of Japanese chestnuts in this country (PL XXII). Other specimens in this collection showed well-developed perithecia and ascospores. The ascospore measurements made at the time, as well as the cultures of the Chinese fungus and the inoculation experi- ments on C. dentata, are described in the previous paper by the writers (76, p. 296). Shortly after this first series of inoculations was made subcul- tures of the Chinese material were sent to several investigators who had been studying the chestnut-bark disease, in order that the Endothia from China might be tested as soon as possible under American conditions by inoculations at various points throughout the known range of the disease. A series of inoculations was made by Prof. J. Franklin Collins at Martic Forge, Pa., on July 14, 1913, using American and grafted Paragon and grafted Japanese chestnut trees. Another series of inoculations, 56 in number, was made at the same locality Septem- ber 10, 1913, by Dr. Caroline Rumbold on grafted Paragon chest- nuts. Twenty inoculations were made on native chestnuts at Ander- son, Pa., October 2, 1913, by Dr. F. D. Heald and R, A. Studhalter. Inoculations with the Chinese Endothia were made at Leesburg, Va., on both Castanea dentata and C. pumila by G. Flippo Gravatt and J. T. Rogers, August 16, 1913. All these investigators made duplicate inoculations with American material, and all agreed that the Chinese fungus was identical in its effects on the host with the American chestnut-blight fungus. Dur- ing the season of 1914 numerous inoculations with material from China were made by the writers at various points in New Hamp- shire, Massachusetts, Connecticut, New York, Delaware, and Mary- land, while others have been made in Rhode Island by Prof. Collins with the same results. ADDITIONAL CHINESE SPECIMENS. Since the publication of the previous paper (76) additional speci- mens of E. parasitica from China have been received from Meyer; one collected at Changli, Chihli Province, China, October 13, 1913, by Mrs. Mary S. Clemens ; a quantity of material collected by Meyer himself in the village of Tachingko, near Taianfu, Shantung, China, March 21, 1914; and another 'collected by him at Yatyeko, Shensi, China, September 2, 1914. A few cankers have also been sent by Meyer, collected by him at Shihbonshan, near Hangchow, Chekiang Province, China, June 26, 1915. The label on this specimen bears the further comment, " very destructive in this locality." Cultures have been made from all these specimens and have invariably proved to be identical with cultures of E. parasitica found in this country. Bui. 380, U. S. Dept. of Agriculture. PLATE XXII. AN OLD CANKER CAUSED BY ENDOTHIA PARASITICA ON A BRANCH OF CASTANEA MOLLISSIMA. Collected by Frank N. Meyer, May 31, 1913, near Santunying, Chihli Province, China. Bui. 380, U. S. Dept. of Agriculture. PLATE XXIII. FIQ. 1. -JAPANESE CHESTNUT AT NIKKO, JAPAN, FROM WHICH THE CHESTNUT BLIGHT FUNGUS (ENDOTHIA PARASITICA) WAS COLLECTED BY F. N. MEYER, ON SEPTEMBER 17, 1915. FIG. 2.— Two BRANCHES OF A JAPANESE CHESTNUT. THE LARGER (TO THE LEFT) WAS BROUGHT TO THIS COUNTRY BY F. N. MEYER, AND FROM IT ENDOTHIA PARASITICA WAS ISOLATED. ENDOTHIA PABASITICA AND RELATED SPECIES. 57 As Tachingko is 300 miles south of Changli, where E. parasitica was first collected by Meyer, and Yatyeko is 500 miles west of Tachingko, it seems highly probable from the collections that E. parasitica is widely distributed in China (fig. 5). Meyer, writing from Hangchow, July 1, 1915, refers as follows to the condition of the chestnuts in that locality : Well, I have a few interesting discoveries to report. First, there are many specimens of Castanea mollissima scattered at the bases and on the lower slopes of the hills around here, and these chestnuts are seriously attacked by the bark fungus, and in my estimation are going to succumb to it these coming years. The chinquapins (Castanea spp.), however, which are very abundant on the higher and more sterile hill slopes, seem to be immune; FIG. 5.- -Outline map of China and Japan, showing the localities in which Endothia parasitica has been found. at least I did not see any evidences of damage or even of attacks. This brings another interesting point to my mind. I was told in Nanking that various missionaries at Ruling, the great summer resort in central China for missionaries, were cutting down their chestnuts, as the tops were all dying, due to borers working underneath the bark. Meyer has since stated to the writers that he believes the de- struction of the chestnut at Kuling is due to Endothia parasitica rather than to borers. In the writers' earlier publication the following statement was made (76, p. 297) : The Chinese organism has thus been shown to be practically identical with the American in all its morphological and physiological characters and in the production of the typical chestnut blight and the pycnidial fructifications 58 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. of the fungus. There is apparently but one other requirement that could be made according to the strictest pathological canons to perfect the proof in this case, and that is the production of typical ascospores of E. parasitica on the lesions produced by the inoculations. The last requirement has now been fulfilled. Specimens collected February 15, 1915, from inoculations made September 20, 1913, on chestnuts in Virginia, near Point of Rocks, Md., with Chinese ma- terial, show perithecial stromata with typical ascospores of E. par- asitica, thus completing the evidence. DISCOVERY OF ENDOTHIA PARASITICA IN JAPAN. More than two years after hi^ original discovery of Endothia parasitica in China (June 3, 1913), Meyer also discovered the fungus in Japan. A brief account of his discovery has already been pub- lished by the writers (78). It may be sufficient here to state that fol- lowing the discovery of Endothia parasitica in China the writers endeavored by correspondence to obtain the fungus from Japan. While not successful in obtaining Endothia parasitica, the writers did receive several specimens of fungi, including species of Endothia on species of Castanea. These, together with several specimens of fungi found on chestnut nursery stock from Japan, make it clear that there are in that country several Pyrenomycetes other than Endothia parasitica more or less parasitic on Castanea. Meyer first discovered the chestnut-blight fungus in Japan at Nikko, September 17, 1915, on wild trees of Castanea crenata Sieb. and Zucc. A photograph of the trees from which he collected speci- mens of Endothia parasitica is shown in Plate XXIII, figure 1, and a branch from which the diseased material brought to the United Sates was taken is shown in Plate XXIII, figure 2. Shortly after Meyer's arrival in Washington in December, 1915, the specimens collected at Nikko were turned over to the writers for study. Examination at once showed cankers and mycelial fans typical of Endothia parasitica. The material also contained typical pycnospores and ascospores of the fungus. Cultures made from single ascospores on various culture media proved to be identical with those of Endothia parasitica found in this country and in China, thus establishing beyond question the identity of the fungus. Meyer's observations as to the resistance of the Japanese chestnuts to this disease are of great interest. He states that the trees vary considerably as regards their p^ower of resistance, but that in general the Japanese chestnut is even more resistant to Endothia parasitica than is the Chinese chestnut (Castanea m-ollissima) . As announced in the same publication (78), Endothia parasitica was collected by Dr. Gentaro Yamada at Morioka, northern Japan. These specimens, which show typical cankers as well as ascospores of the fungus, were received by the writers on January 8, 1916. ENDOTHIA PARASITIC A AND RELATED SPECIES. 59 PRESENT DISTRIBUTION OF ENDOTHIA PARASITICA IN AMERICA. The present range of Endothia parasitica in America, as shown by the map (fig. 4), is probably merely the extent to which it has been able to spread in the time since it was first introduced. Whether Endothia parasitica was introduced into one locality or several is uncertain, but the studies of Heald (40, 41) and others have shown clearly that the spores of E. parasitica are carried by the wind, by insects and birds, and on nursery stock, which would account for its wide distribution and for its occurrence in isolated localities, long distances away from the main body of the disease. It also makes it seem probable that the fungus wrill continue to spread with some rapidity. Certainly, there is no evidence that any factor, climatic or other- wise, is likely to prevent the spread of this fungus into the large area of chestnut south of its present range. On the contrary, the duplicate inoculations made by the writers show clearly that the fungus grows more rapidly at the southern limit of its present range than farther north, where it is much more common. The longer growing season in the South is also no doubt an important factor. In this connection, it may be noted that Koppen (46), in his map of the vegetation regions of the earth, places the portion of China where EndotMa parasitica has been found indigenous in the same climatic region as that portion of the United States where it is now doing such destructive work. He designates this region as the " Hickory " division of the mesotherms. HOST RELATIONS OF THE SPECIES OF ENDOTHIA. ENDOTHIA GYROSA. Endothia gyrosa occurs commonly on Liquidambar, Fagus, and Quercus, occasionally on Castanea, and has been found on Vitis in Alabama, but the writers were unable to obtain fresh material from this host. While Fagus and Quercus are, of course, closely related, it seems remarkable that a fungus should be abundant on hosts so different as Liquidambar and Quercus, yet so rare on any other host as to be only once reported. It seemed possible, indeed, that the fungus on Liquidambar, while morphologically and culturally identical with that on the various other hosts, might prove to be physiologically dif- ferent. In order to obtain more definite information on this point, several series of cross inoculations were made. It had been observed that Endothia gyrosa was found most fre- quently on the cut or broken ends of branches or on exposed, bruised, or broken roots. In making inoculations, therefore, a small branch, 60 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. 1 inch or less in diameter, was cut off about 6 inches from the main trunk. Mycelium from corn meal in flasks was placed on the cut end of the stub and covered with wet cotton, over which oiled paper was tied. In about two weeks the paper and cotton were re- moved. In all cases, branches similar to those inoculated were cut as checks. TABLE III. — Inoculations with Endothia gyrosa. Source of fungus and date. Host inocu- lated. Number of inocu- lations. Number success- .fuL Remarks. Fagus: May 8 1913 Castanea 6 3 Pycnospores first observed on Oct. 16. May 29 1913 3 3 Pycnospores first observed on Aug 29 for Sept 15 1913 Liquidambar . 5 2 two and on Oct. 10 for the third. No growth until the spring of 1914; pyc- Do Quercus.. 4 2 nidia scattered and small on Oct. 13. No growth until spring; well developed on Apr 2 1914 Fagus. 0 Oct. 13, 1914. Do Quercus 0 Do Castanea 2 Pycnldial stromata well developed on Oct. May 23 1914 . .do 4 13, 1914. Do. Do Liquidambar . 0 Do Quercus * 4 0 Do Fagus 4 3 Do. Quercus: May 29 1913 do.. .. 3 3 Pycnospores first observed on Aug. 29, 1913. Do Liquidambar . 4 2 Very slight indications of growth on Aug. Sept 15 1913 .do 8 0 29, 1913; a few pycnidia with spores on Oct. 16. Do Castanea 4 2 Large well-developed pycnidia on Oct. 13 Apr 2 1914 Fagus 4 o 1914. Do .. Quercus l 4 0 Do Castanea 4 4 Large abundant pycnidial stromata on Oct. May 23 1914 do 4 4 13, 1914. Abundant well-developed pycnidial stro- Do... Liquidambar . 4 0 mata on Oct. 13, 1914. Do Quercus 1 4 o Do Fagus. 4 3 Castanea: May 29, 1913 .. .do 3 3 Pycnospores first observed on Aug. 29, 1913. Do.. Liquidambar 3 3 Slight indications of pycnidial formation on Apr 2 1914 Fagus 4 o Aug. 29, 1913; pycnospores on all on Nov. 17, 1913. Do Quercus 1 . 4 1 Large well-developed pycnidial stromata Do Castanea 4 3 on Oct. 13, 1914. Scattered fairly well-developed pycnidia May 23, 1914 do 4 4 on Oct. 13, 1914. Abundant well-developed pycnidia on Oct. Do Liquidambar 4 o 13, 1914. Do 4 o Liquidambar: May 29, 1913 Fagus 3 o Do Liquidambar 3 3 Pycnospores first observed on Aug. 29. Sept. 15, 1913 Fagus. 8 5 No evidence of growth until the spring of Do Castanea g 2 1914; pycnidia few and small on Oct. IS. No growth until the spring of 1914' pyc- Do. Quercus 6 o nidia small on Oct. 13. Apr. 2, 1914 . . . Fagus 4 o Do.... Quercus l 4 o Do Castanea 4 o May 23, 1914 Do do Liquidambar 4 4 0 4 Abundant pycnidia on Oct. 13 1914. Do Quercus J . . . 4 0 Do Fagus 4 o I 1 The species used in this case was Quercus prinus, which proved to be an exceedingly unfavorable host for Endothia gyrosa. ENDOTHIA PARASITIC A AND BELATED SPECIES. 61 Inoculations with Endothia gyrosa were also made on numerous hosts from which it had never been reported. Six or more inocu- lations were made on each host, in the manner described above, ex- cept that a part of each series was left unwrapped. The following inoculations showed no growth whatever: Those made in Virginia, April 4, 1914, on Cornus florida, Fraxinus americana, Juglans cinerea, Ilex opaca. Sassafras variifolium; in Maryland, April 17 and 22, 1914, on Carya glabra, Cornus florida, Liriodendron tulipifera, Nyssa sylvatica, Sassafras variifolium, and Quercus alba; and in New York, July 11, 1914, on Betula alba, Prunus serotina, Populus trem- uloides, Rhus glabra, Salix sp., and Sassafras variifolium. On Acer pennsylvanicum and Carya two out of the six inoculations developed a few stromata. These were found only on the tissue injured by the cut and there was no evidence of parasitism. On Castanea, Fagus, Quercus, and Liquidambar, however, a branch inoculated as described above dies back rather faster than the checks. This would indicate, as suggested by Clinton (18, p. 419), that E. gyrosa is a weak parasite ; that is, that it is able to invade injured and dying tissue. It is evident from Table III that Endothia gyrosa coming from any of the four hosts named will, under favorable circumstances, grow on any of the others. Several other interesting facts are brought out by the table. Inoculations made with material from Liquidambar grew in general more rapidly on Liquidambar than on any of the other hosts. In many cases, material from, Liquidam- bar failed to grow on Castanea, Fagus, and Quercus, and even when inoculations were successful growth was somewhat slower and pyc- nidial production less abundant. On the other hand, inoculations from Fagus, Quercus, and Castanea usually grew less rapidly on Liquidambar than on any of the other three hosts. This is, of course, what would be expected from the systematic relationships of the host species, and while the inoculations made are too few to permit any definite conclusions they are nevertheless suggestive. As shown by Table III, Quercus prinus proved a very unfavorable host for Endothia gyrosa. In all cases inoculations made in the fall (Sept. 15) failed to show any growth until the following spring. This corresponds with the results in inoculations of Endothia parasitica, but it is, of course, impossible to determine whether this failure to grow is due to the dormant condition of the host or to unfavorable weather con- ditions. Perhaps correlated with the results just noted are the unusually poor results obtained from inoculations made in the early spring. It will be noted that inoculations made on April 2, 1914, were in general much less successful than those made on May 23, 1914, in exactly the same locality and in many cases on the same hosts. 62 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. ENDOTHIA SINGULARIS. The material of Endothia singular'^ distributed by Sydow as Calo- pactis singularis was on Quercus gambellii Nutt. The writers have seen abundant material on this species as well as specimens on Q. utahensis (A. DC.) Rydb., Q. leptophylla Rydb., and Q. nitescens Rydb. Specimens on the latter two hosts were sent by Bethel, who, in a letter, reports finding this species also on Q. pungens Liebm. All of these species except Quercus leptophylla are chaparral- forming shrubs growing at an elevation of 4,000 feet or more. There is at present no evidence that the fungus is parasitic on any of the species. Inoculations with the mycelium of Endothia singularis were made on Fagus and on Quercus alba, Q. velutina^ Q. rubra, and Q. palustris, as well as on Q. Uidfolia on Overlook Mountain in the Catskills. No growth has, however, been noted in any case. ENDOTHIA FLUENS. When these investigations were commenced, the writers thought that the Endothia found in Europe might be the same as Endothia parasitica found in America. Inoculations were accordingly made in Maryland during October, 1912, with cultures from material col- lected on the chestnut by the senior writer at Stresa, Italy, and Etrembieres, Switzerland, using material of E. fluens sent by P. J. Anderson from Pennsylvania; also material of that species and of E. parasitica collected in Virginia as checks. In this case, as in all others where no special mention is made of the method, inoculations were made by cutting through the bark to the wood with a sharp knife. The inoculating material was then inserted with a freshly cut twig and the wound tied up either with cord or rubber bands. If cord was used it was cut away within two to four weeks. The rub- ber bands became loosened by exposure to the weather within about the same time. Inoculations were made with all the above material on sprouts of Castanea dentata and Quercus prinus. The results are summarized in Table IV. TABLE IV. — Inoculations of Endothia in Maryland in October, 1912. Fungus. Host inoculated. Number of inocu- lations. Number showing growth. Endothia parasitica Castanea dentata 32 28 Do 6 o E. fluens: European Castanea dentata 14 14 American. . . do . .. 26 23 Do Quercus prinus 12 9 ENDOTHIA PARASITICA AND BELATED SPECIES. 63 The inoculations were examined every 10 days until December 1 and monthly thereafter throughout the winter. There was no per- ceptible growth until the last of April, when several of the inocula- tions of Endothia parasitica showed slight sunken areas. By May 20 all inoculations checked as showing growth (last column of table) showed the slight yellowish elevations of the bark which indicate the beginnings of pycnidia. On August 30 all the inoculations of E. parasitica checked as showing growth had spread rapidly and attacked the living tissues of the host, producing typical cankers with mycelial fans and abundant pycnidia. No signs of growth were noted in the inoculations of Endothia flwns until about the middle of May, 1913, when most of them showed signs of pycnidium formation. By August 30 all those marked as showing growth had produced characteristic pycnidia with spores, which when cultured proved to be typical E. fluens. In no case, however, did this fungus spread for any appreciable distance beyond the injured portion or show signs of active parasitism. These results agree with those given by Anderson and Anderson (2, p. 206) with American material of E. fluens, and have since been fully con- firmed by further observation. During the summer of 1914 about 1,100 inoculations of Endothia fluens from both European and American sources and of E. fluens 1 mississippiensis were made on Castanea sprouts. In no case was there any evidence of active parasitism, as in E. parasitica. Although Endothia fluens has been found in Europe on a con- siderable number of deciduous host plants (as recorded on p. 18), the writers have thus far failed to find it in this country on any except Castanea and Quercus. It seemed possible that the European strain of the fungus might be somewhat more plurivorous1 in its habits than the American. In order to throw some light on this point, the following inoculations were made : On March 31, 1914, 10 inoculations were made, half of European and half of American material, at Francis, Md., on the following hosts: Alnus rugosa, B etui a nigra, Carpinus caroliniana, Gary a glabra, Fagus grandifolia, Lirio- dendron tulipifera, and Liquidambar styraciflua. Pycnidia appeared only on Carya glabra and Carpinus caroliniana. Of the inoculations which actually produced pycnidia, four on Carpinus and three on Carya, one of each was the European strain. On April 22 inoculations were made with American material of E. fluens at Kensington, Md., on Acer rubrum, Carya glabra, Cornus florida, Fagus grandi- folia, Prunus serotina, Quercus prinus, Sassafras variifolium, Vaccinium sp., 1 This term is proposed to apply to fungi occurring on two or more hosts or substrata and may be applied to all fungi except true parasites. It is derived from plus (plur-), more, and vorare, to devour. Compare omnivorous already in use for fungi. The term pleioxonous might be derived from De Bary's proposed word pleioxony and applied to true parasites having the power to invade more than one species of host plant, and the term plurivorous restricted to nonparasitic organisms. BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. and Vitis sp. Of these, Acer rubrum and Carya glabra gave numerous small pycnidia. On July 10 the following hosts were inoculated at Woodstock, N. Y., with E. fluens from Europe : Acer rubrum, A. pennsylvanicum, Carya ovata, Corylus americana, Fraxinus americana, Hamamelis virginiana, Kalmia latifolia, Popu- lus grandidentata, Prunus serotina, RJius glabra, Salix sp., Sassafras variifo- lium, and Syringa vulgaris. Each host was inoculated in six or seven places, but all failed to develop except two inoculations on Acer pennsylvanicum and one on Corylus americana. The results cited above are so largely negative that they prove very little except that the European strain shows no special affinity for these hosts in America. ENDOTHIA FLUENS MISSISSIPPIENSIS. Only five collections of Endothia fluens mississippiensis have thus far been made, three on Costarica dentata and two on Quercus sp. From the results of the inoculations its host relations appear very similar to those of E. fluens. The results are; shown in Table V. TABLE V.- -Inoculations with Endothia fluens mississippiensis on Castanea and Quercus. Source of culture. Host inoculated. Date. Number of inocu- lations. Number showing pycnidia. Castanea Castanea Jan 20 1912 8 8 Do... do May 8, 1913 4 4 Do do do 4 4 Do... Quercus prinus do 9 7 Do Castanea . Apr 18, 1914 12 10 Quercus do do 12 10 The inoculations of January 20, 1912, showed no signs of growth until early in May, when the first signs of pycnidium formation were observed. The inoculations with Endothia fluens mississippiensis made May 8, 1913, showed within three weeks discolored areas near the cut which were larger than those about the check cuts. On July 25, 1913, all of the inoculations of E. fluens mississippiensis marked "successful" showed the beginnings of pycnidium formation. By August 30, 1913, they were producing pycnospores, which when cul- tured proved to be E. fluens mississippiensis. Inoculations were made in April, 1914, for the purpose of com- paring the material collected on oak with that collected on chest- nut. No difference was detected,*and there was no indication of active parasitism. This form behaved in this respect exactly as did the E. fluens from Virginia both on Castanea dentata and Quercus prinus. A series of inoculations parallel to that made with E. fluens was made with E. fluens mississippiensis. The same hosts were used, and in most cases the dates and places of the inoculation were the same. The results of all that showed any growth are given in Table VI. ENDOTHIA PAEASITICA AND RELATED SPECIES. 65 TABLE VI. — Inoculations with Endothia ftuens mississippiensis on Acer and Carya. Location. Host. Number of inocu- lations. Number showing pycnidia. Woodstock N Y Acer rubrum 6 •j Do Q 2 Francis, Md do 6 I Kensington, Md 1 1 Do 2 2 As in Endothia fluens the growth was confined to the injured tis- sues, and there was no evidence of parasitism. ENDOTHIA TROPICALIS. The material of Endothia tropicalis from which the writers se- cured their cultures, was collected by T. Fetch in Ceylon. As the species of Endothia in the Northern Hemisphere are chiefly on members of the Fagaceae, Fetch's statements with regard to hosts are of considerable interest. In a letter of March 6, 1914, he writes : We have no Fagacese native in the island. We have introduced various species of Quercus and Castanea, but subsequent to Thwaite's discovery of this fungus. I do not think there can be any doubt that the fungus is native to Ceylon * * * Of the speciments now sent * * * those in the packet * * * are from a tree which was producing shoots from the base. This tree is Elaeocar- pus glandulifer Mast. From the bark and habit, I believe that all my " finds " of Endothia have been on this species. In the accounts of the American ckestnut disease," I 'notice that several authors speak of " cankers," and give their rate of growth. I never see "cankers" (Krebs) on the Ceylon trees. The bark appears to die regu- larly and smoothly from above downward, and is quite unbroken except for the minute cracks through which the stromata emerge. Inoculations. — As already noted, ascospores of Endothia tropi- calis resemble those of E. parasitica even more closely than do those of E. fluens. This fact, together with its similarity on culture media and its oriental origin, led the writers to fear possible parasitic tendencies. Inoculation experiments were accordingly made only on the chest- nut and under carefully guarded conditions. In all, about 30 inoculations were made on 2-inch chestnut sprouts, using the methods described for other species. Of 25 inoculations made in May and June, practically all had de- veloped a few pycnidial stromata by October 20. These stromata were a somewhat brighter orange than those of E. fluens or E. fluens mississippiensis, and the spores when cultured produced typical E. tropicalis. In no case, however, was there any evidence of parasitism. 43737°— Bull. 380—17 5 66 BULLETIN 380, U. S. DEPARTMENT OF AGEICULTURE. ENDOTHIA PARASITICA ON HOSTS OTHER THAN CASTANEA. The first collection of Endothia parasitica on a host other than Castanea of which the writers have any knowledge is that made by J. Franklin Collins at Martic Forge, Pa., June 30, 1909. As an- nounced by Dr. Metcalf at the Boston (December, 1909) meeting of the American Phytopathological Society, the specimen consisted of a small dead branch of Quercus velutina with several spore tendrils typical of E. parasitica. This material, which consisted of a terminal branch with leaves still retained, was at once sent to the laboratory at Washington, and cultures obtained from it were sub- sequently used in making numerous inoculations on Castanea dentata on Long Island, N. Y., in July, 1909. On November 17 of the same year, Metcalf reported that the inoculations were entirely successful and had produced typical lesions, thus establishing without question the identity of the fungus. Fulton (37, p. 53) reports E. parasitica on the dead bark of Quer- €us alba and Quercus velutina, but found no evidence that the fungus produces in any sense a disease of such trees. Clinton (18, p. 428) mentions cultures from three different species of Quercus and (p. 376) reports specimens on Quercus alba, Q. rubra, and Q. velutina. Anderson and Babcock, as quoted by Anderson and Rankin (6, p. 564), found Endothia parasitica on Quercus velutina, Q. alba, Q. prinus, Rhus typhina, Acer rubrum, and Cory a ovata, but it seemed parasitic only on Quercus alba. They made inoculations with mate- rials isolated from Castanea on Quercus prinus, Q. velutina, Q. alba, Q. cocdnea, Rhus typhina, Acer rubrum, Liriodendrontulipifera,^^ Carya ovata. Two trees of Rhus were girdled and killed by the growth of the fungus. On Quercus alba the fungus seemed slightly parasitic, but none of the trees were killed. The fungus grew and produced spore horns on the wounded tissue near the point of inocu- lation on all the hosts except Acer and Liriodendron. Rankin (62, p. 238) also made inoculations with Endothia para- sitica from Castanea on Quercus prinus. Q. rubra, Q. alba, and Q. cocdnea. He found that the mycelium advanced into the living tissues for a short distance in a few cases, but that in no case were typical cankers formed. Py^cnidia were produced abundantly on the injured tissues of all the hosts. During the course of this work only four specimens of Endothia parasitica on hosts other than Castanea have come to the writers. One was on chestnut oak (Quercus prinus) collected by F. W. Besley, at Towson, Md., December 26, 1911; one from Quercus velutina, at Germantown, Pa., as well as one from white oak (Quercus alba), at Kennett Square, Pa., were collected by S. B. Detwiler; and one from dead maple, Acer sp., at Florence, Mass., by Roy G. Pierce. ENDOTHIA PARASITICA AND BELATED SPECIES. 67 The specimen collected by Besley on Quercus prinus showed the fan- shaped mats of mycelium typical of E. parasitica on Castanea spe- cies. The fungus had apparently girdled the tree. The specimen on Quercus alia, collected by Detwiler, was similar to one on Quercus prinus in appearance and came from a dead tree which had appar- ently been killed by the growth of the fungus. The specimens on Acer sp. and on Quercus alba were received in the spring of 1914, and cultures isolated from them were used in making inoculations for the purpose of determining whether the fungus had either lost or gained in virulence by passing through other hosts. INOCULATION EXPERIMENTS. The cultures secured from Acer and Quercus, together with one made from Castanea at about the same time, were inoculated into three separate sprouts of Acer rubrum, Castanea dentata, and Quer- cus prinus. The sprouts chosen were of nearly the same size, 2 inches in diameter, and similarly situated, and each was inoculated in five places, with two check cuts above. The inoculations were made the usual way on March 31, 1914, and were examined at least once a month during the summer. None of the inoculations on Quercus produced any growth what- ever. On Acer the inoculations with the culture from Quercus all failed to develop; one of the inoculations with the culture from Acer showed a few pycnidia, while four of the inoculations with material from the chestnut developed a few pycnidia. On Castanea the three series of inoculations were almost identical, every inocula- tion producing a typical canker. Of course, these inoculations are too few to be conclusive, but it is evident that there was no decrease in virulence on the chestnut in passing through Acer or Quercus and that no particular affinity for either Acer or Quercus was gained. On the maple, in fact, the culture direct from chestnut produced the most growth. In addition to those listed above, numerous inoculations were made in order to determine whether EndotMa parasitica had any parasitic tendencies on other deciduous hosts. These inoculations were all made during the spring of 1914 by the usual method of cutting well through the bark and inserting mycelium and spores from a pure culture, usually on corn meal. The wounds were then wet, some bound with wet cotton, others with paraffin paper, and about half were left unwrapped. Seven or more inoculations were made on April 4 in Maryland on Alnus rugosa, Betula nigra, Carpinus caroliniana, Fagus grandi folia, Kalmia latifolia, Liriodendron tulipifera, and Liquidambar styraci- flua, none of which developed. Inoculations were also made on April 68 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. 22 in this locality on Acer rubrum, Carya glabra, Cornus florida, Fagus grandifolia, Liriodendron tulipifera, Quercus prinus, Sas- safras variifolium, Vaccinium sp., and Vitis sp. without success. On April 18, the following hosts were inoculated in Virginia : Acer rubrum, Betula nigra, Benzoin aestivale, Carpinus caroliniana, Carya glabra, Cornus florida, Fag us grandifolia, Liriodendron tulipifera, Prunus serotina, Quercus alba, Ulmus americana, and Vitis sp. Each host was inoculated in from four to six places. Of these, pycnidia were produced only on Acer rubrum, Carpinus, and Lirio- dendron. A similar series was made on the same hosts in the same place on May 27. Inoculations on one tree of Quercus alba showed undoubted evidence of parasitism and is described below. On July 9 and 11 from five to fourteen inoculations were made on each of the following hosts at Woodstock, N. Y. : Acer rubrum, Betula alba, Carya ovata, Fagus grandifolia, Frawinus americana, Hamamelis virginiana, Juglans cinerea, Kalmia latifolia, Nyssa syl- vatica, Ostrya virginiana, Populus grandidentata, Prunus serotina, Rhus typJiina, Quercus rubra, Salix sp., Sambucus canadensis, and Sassafras variifolium. Pycnidia appeared on Acer rubrum and Ostrya only. The fungus made considerable growth on two plants of Rhus typhina, partly girdling branches one-half inch in diameter and producing distinct fans. The fans were, however, much smaller than those usually found in Castanea. Inoculations were made at Avon, Conn., July 15, on Acer saccharum, Betula alba, Carya glabra, Cornus florida, and Ostrya virginiana. Pycnidia developed only on Ostrya. The successful inoculations with Endothia parasitica are shown in Table VII. TABLE VII.- -Successful inoculations in IfUSi with Endothia parasitica on hosts other than Castanea. Locality. Date. Host. Number of inocu- lations. Number success- ful.^ Virginia... Apr 18 Acer rubrum 9 7 Do do g 2 Do . . .do. Liriodendron tulipifera g 1 Do May 27 Quercus alba 4 4 New York July 11 Acer pennsylvanicum 14 4 Do do g 2 Connecticut July 15 do. 15 4. 1 Inoculations producing pycnidia are classed as successful. It must be noted that while pycnidia were produced in the cases listed as successful, there was no indication of parasitism, nor did the growth extend beyond the tissue injured by the cut except in Quercus and Rhus, Out of about 400 inoculations with Endothia parasitica on hosts other than Castanea, about TO of which were made on different ENDOTHIA PARASITICA AND BELATED SPECIES. 69 species of Quercus, chiefly Q. prinus and Q. alba, only one case has been noted in which the fungus assumed a typically parasitic role. The data in this case may be summed up as follows : Four inocula- tions were made May 27, 1914, on a small tree of Quercus alba* This tree was suppressed, and although when cut down it showed about 30 annual rings it was only 16 feet high and about 2 inches in diam- eter. It was in a moist, shady locality close beside a stream, and in spite of its small size was apparently healthy. The inoculations were made in the usual way from a culture of E. parasitic® on corn meal. On August 1 it was noted that all four inoculations were pro- ducing pycnidia, and in at least one case typical fans had been developed. On October 15 all four cankers had more than half girdled the seedling. No observations were made during the winter, but at the time the leaves had reached half the normal size, in the spring of 1915, the tree was completely girdled. On July 1 this tree presented an appearance closely similar to that of a small chestnut tree girdled by EndotMa parasitica. All the leaves above the point of inoculation were dead and remained attached to the branches. Below the girdled portion, water sprouts had developed, as has been frequently described for chestnut trees affected with E. parasUica. Cultures made from this tree showed the fungus to be typical of E. parasitica. Whether this case of parasitism was due to unusual virulence on the part of the fungus or to unusual susceptibility on the part of the host is, of course, merely a matter of conjecture ; the latter alternative seems, however, somewhat more probable, as other inoculations with this strain of the fungus on Q. prinus and Q. alba failed to show similar results. In addition to the above, a somewhat similar observation has been made by the writers near Amherst, Mass. In connection with other work, a sprout of Quercus prinus about an inch in diameter was inoculated with Endothia gyrosa on July 15, 1914. When this inocu- lation was made the tree was partly (about one-fourth) girdled. E. gyrosa developed normally and by October 1, 1914, had produced several pycnidial stromata. No change was apparent when the inocu- lations were examined in May, 1915. E. parasitica was abundant in the region, however, and apparently gained entrance through the cuts originally made, for when the plat was next visited, August 17, 1915, the sprout appeared quite dead, though still retaining its full-sized dead leaves. Further examina- tion showed numerous pycnidia of E. parasitica in addition to those of E. gyrosa near the region of the original inocul ation. The pycnidia of E. parasitica were on all sides of the stem, while those of E. gyrosa were confined to the portion above the cuts made in inoculating. The mycelial fans typical of E. parasitica were abundant also. These 70 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. observations leave no doubt that the tree was girdled and killed by E. parasitica. Endothia parasitica in exceptional cases undoubtedly attacks other hosts than Castanea, producing cankers and sometimes causing the death of the host. The results of the inoculations just recorded appear to indicate that some unusual conditions of host or parasite must obtain in such cases. Whether such a combination of conditions or factors will ever become sufficiently frequent to lead to serious destruction of Quercus or other forest trees remains to be determined. ENDOTHIA PARASITJCA ON CASTANEA SPP. Although found occasionally on species of other genera, Endothia parasitica is dangerously pathogenic only on members of the genus Castanea. The parasitism of this fungus on the American chestnut (Castanea dentata) was first proved by Murrill (57) and has since been demonstrated by numerous investigators. When Endothia parasitica was discovered in the United States it was considered by some investigators to be a native fungus which had suddenly become parasitic, and various theories were advanced to account for the supposed unusual susceptibility of the host. As enumerated by Clinton (18, p. 391), the factors suggested include winter injury, drought injury, fire injury, weakened condition due to continued coppicing, and reduced amounts of tannic acid due perhaps to weather conditions. Continued study by many investigators in different localities has, however, fully confirmed the observation originally made by Met- calf and Collins in 1910 (53) that " a debilitated tree is no more subject to attack than a healthy one " and that Endothia parasitica is actively parasitic on the healthiest specimen of Castanea dentata in case there is opportunity for Avound infection. The writers have personally made over 1,200 inoculations of E. parasitica on Castanea dentata without finding a single individual that showed any re- sistance. CASTANEA ON LIMESTONE SOILS. Not only are all trees susceptible, but so far as is known no con- dition of soil, altitude, or- moisture renders them more resistant to the disease. The idea has been held by some writers that chestnuts grown on limestone soils were immune to the disease, and the plant- ing of chestnut orchards on such soils was advocated. This view is held by Gulliver (38, p. 53), who sums up his observations in two regions in Pennsylvania as follows: In every series of tracts taken from limestone to overlying shale soils, the percentage of blight is least at a comparatively short distance * * * from the edge of the limestone. Tracts on soils derived from limestone which show the highest percentage of blight seem to be those where the soil has ENDOTHIA PARASITICA AND RELATED SPECIES. 71 become acid from underground drainage. Chestnut trees on soils derived from other alkaline rocks show less blight than is found in the trees on shale soils with limestone underneath. On the other hand, Detwiler (24, p. 67) reports observations in the Lizard Creek valley which seem to show that these relations do not always occur. He says — A belt of limestone borders Lizard Creek valley on the 'south, and the per cent of infection is as high in that region as elsewhere. Infection centers have been found near limestone quarries, where the roots of the chestnut pene- trated to bedrock. Actual proof or disproof of the truth of this idea was peculiarly difficult, since chestnut is but rarely found growing naturally on calcareous soils. During the summer of 1914, however, a careful study of the chestnut on certain portions of limestone areas in west- ern Maryland and western Connecticut was made. These localities were chosen because they were convenient in connection with other work, the blight had been present for several years in both States, and thorough State geological surveys made the location of the lime- stone areas very easy. The two States also are sufficiently far apart to eliminate sources of error that might arise from local weather conditions. In western Connecticut chestnut was abundant on glacial till over the Stockbridge limestone of this region. Chestnut was also grow- ing directly over limestone at various points near Danbury, Twin Lakes, Chapinville, and Lakeville. Several localities near the latter place were kindly pointed out by Dr. George E. Nichols. Near Dan- bury every tree examined showed the blight in a more or less ad- vanced stage, while near the other towns, all in the northwest corner of the State, nearly 50 per cent of the trees were blighted. About 30 inoculations were made on sprouts in this region, and all except two developed cankers quite as rapidly as did check inocula- tions made on the trap ridge west of Hartford. Chestnut is very rare on the Shenandoah limestone in the Hagers- town and Frederick valleys of western Maryland. A number of chestnut trees were, however, located growing on limestone soil near Frederick Junction and Adamstown in the Frederick valley. The disease was already established west of Adamstown, where 20 per cent of the chestnuts were either diseased or dead. Twenty-two in- oculations were made on nine chestnut sprouts in these two regions^ and all developed typical cankers quite as rapidly as the checks made in similar sprouts growing over Baltimore gneiss 50 miles east. RECESSION OF THE CHESTNUT IN THE SOUTHERN STATES. While it has been definitely proved that Endothia parasitica is pathogenic on healthy chestnut trees, one of the points brought for- 72 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. ward by the advocates of the " weakened host " theory seems to be fully established; that is, that the chestnut trees have suffered se- verely in the southern Appalachian regions previous to the present epidemic, in some cases being practically exterminated, so that the range is now considerably less than formerly. The evidence on this point has been summarized by Clinton (18, pp. 408-413). Various writers quoted by him cite fire injury and borers and other insects as causes for this recession. Long (48, p. 8) considers a root rot due to Armillaria mellea as " very probably an important factor in the gradual recession of the chestnut" in North Carolina, it seems probable that all of the above-mentioned factors, and perhaps others, have played a part in the destruction of the chestnut in this region. RELATIVE SUSCEPTIBILITY OF SPECIES OF CASTANEA. The importance of Castanea dentata as a timber and nut tree and its abundance in eastern North America, where the blight is preva- lent, has made the chestnut blight an object of much investigation. Descriptions of the nature and importance of the disease, the rate of its spread, methods of distribution, and attempted methods of control have been given in detail by Anderson (1-5) , Clinton (12-15) , Heald (39-41), Metcalf (51 and 52), Metcalf and Collins (53), Kan- kin (62), and others. It may be sufficient here to state that the fungus enters the host through a wound in the bark, probably never or very rarely through lenticels or natural cracks, grows chiefly in the cambium, penetrating for only short distances into the wood, and kills the tree or branch by girdling. Once a tree is attacked, it is only a question of time till it succumbs. The chinquapin (Castanea pumila) wras found by Murrill (58) in 1908 to be attacked by EndotMa parasitica. Rogers and Gravatt (65) in 1915 made inoculations of E. parasitica on C. pumila and found that the parasite grew as rapidly on this host as on C. dentata. They attribute the apparent resistance of the chinquapin to its com- parative freedom from bark injury, a view also held by other writers. Pantanelli (60) and Metcalf (52) have proved that the European chestnut is readily susceptible to the disease. The only chestnuts thus far observed which show any resistance to EndotMa parasitica are those of oriental origin. Metcalf (51) first pointed out the resistance of the Japanese chestnut. This observation has since been confirmed by Clinton (18, p. 375), who " failed to produce the disease in a Japanese variety in the [Conn.] station yard, although the bark was inoculated in 16 different places." Van Fleet (84), in describing the spread of the chestnut blight in his breeding plats at Washington, D. C., says (p. 21) : " The Asiatic chestnuts and the chinquapin- Asiatic hybrids are plainly highly resistant." ENDOTHIA PARASITIC A AND RELATED SPECIES. 73 Morris (56) sums up eight years' observation of the effect of the chestnut blight on 26 species and varieties of chestnuts at Stamford, Conn., as follows: Every one of the 5,000 American chestnut trees became blighted * * * None of [the grafted varieties or seedlings of European and Asiatic varieties appear] to be as vulnerable as the American chestnut, but most of mine are now dead. Korean chestnuts and chestnuts from the Aomori regions in Japan resisted the blight until six years of age. Since that time they have shown a marked tendency to blight, but resist it better than does the American chestnut * * * None of the American species of chinquapin * * * has blighted with the exception of two limbs * * * None of the specimens of Castanea alnifolia [or] * * * of Castanea mollissima has blighted, but these latter include only five trees. These observations as to the resistance of the oriental varieties of chestnut when grown in America are of particular interest in con- nection with the observations of Meyer in the region where he dis- covered Endothia parasitica native. In his letter to Fairchild, writ- ten from Santunying, China, June 4, 1913, Meyer makes the following notes with reference to the effect of the blight in that region : This blight does not by far do as much damage to Chinese chestnut trees as to the American ones * * * Not a single tree could be found which had been killed entirely by this disease, although there might have been such trees which had been removed l>y the ever-active and economic Chinese farmers * * * Dead limbs, however, were often seen and many a saw wound showed where limbs had been removed * * * The wounds on the majority of the trees were in the process of healing over * * * Old wounds are to be observed here and there on ancient trees. Meyer's photographs taken near Santunying substantiate his state- ments. Certainly no specimens of C. dentata in a blight-infested region in this country could survive to the age of the Chinese chest- nuts shown in his photographs. That the Chinese chestnuts are by no means uniformly resistant, however, is clearly shown by Meyer's later notes. On the label of a package of Endothia parasitica collected on chestnut at Tachingko, Shantung, China, March 21, 1914, he writes, "Trees very severely attacked, many dying off," and in a letter written from the same place he says, " A serious canker ; many of the trees here were killed by it," Further evidence that the virulence of Endothia parasitica on Chi- nese chestnut differs in different parts of China is found in subse- quent communications from Meyer. From a point near Chingtsai, Chekiang, China, on July 15, 1915, he writes: "All around Hang- chow and west of it one finds the chestnut trees seriously attacked by this destructive bark fungus." On July 11, 1915, near Changhua, Chekiang, China, he com- ments, "With the exception of near Taianfu, Shantung, chestnuts 74 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. are much more severely attacked in the Chekiang Province than either in Chihli, Shansi, or Shensi. Could the greater humidity of central China be of assistance to a more vigorous development of this destructive fungus?" COMPARISON OF HOST RELATIONS. It will be seen from the above description of the host relations of the various species that while some other members of the genus (E. gyrosa, e. g.) may have slight parasitic tendencies, Endothia parasitica alone is an active parasite. The contrast is still more striking in the section of the genfts to which E. parasitica belongs, for E. fluens and E. fluens mississippiensis, which resemble E. para- sitica so closely in their morphological characters, and to a less degree on culture media, and are common on Castanea, are almost purely saprophytic. This fact is established by the work of Ander- son (2), Clinton (18), and others, and by two years' field observa- tions and several thousand inoculations made by the writers and their colleagues. The host relations of the parasite are equally striking. Although Endothia parasitica is so pathogenic on Castanea dentata that this tree has been practically exterminated over several hundred square miles of its natural range and its extinction is threatened, the fungus has been only occasionally found as even a weak parasite on the closely related genus Quercus, and never, to the writers' knowledge, on Fagus. During the course of this work the writers have been continually impressed with the possibilities of a physiological study of E. para- sitica and one or more closely related species which might throw some light on the fundamental question of the nature and cause of parasitism. No other case is known to the writers of a virulently parasitic fungus and a closely related purely saprophytic one which will grow readily and fruit on a large variety of artificial media, which are readily distinguishable on those media, and remain con- stant for hundreds of generations. SUMMARY. The pathological and economic importance of this group of fungi was first recognized when the chestnut-blight fungus was discov- ered in New York in 1904. This organism was first referred to the genus Diaporthe, but was later shown to belong to the genus Endothia. The specific identity, relationships, and native home of this para- site were at first uncertain. Some pathologists considered it a native organism which was attracting attention and causing injury chiefly ENDOTHIA PARASITICA AND BELATED SPECIES. 75 by reason of the weakened condition of the chestnut trees. Others believed it to be of foreign origin. Its recent discovery in China and Japan has settled this question. To determine positively the identity of the organism, a thorough study was made of the types or authentic specimens of all the species of Endothia obtainable. As a result of this work a revision of avail- able species of the genus is presented. This is based upon the field and laboratory study of over 600 collections. Over 4,000 cultures have also been studied. Endothia gyrosa (Schw.) Fr. is the type of the genus, which is naturally divided into two sections, chiefly by the character of the ascospores. In section 1 they are short, cylindric to allantoid, and continuous or only pseudoseptate. This section contains two species, E. gyrosa and E. singularis. Section 2 has oblong-fusiform to oblong-ellipsoid uniseptate as- cospores. This contains four species and one variety, Endothia fluens, E. fluens mississippiensis, E. longirostris, E. tropicalis, and E. parasitica. E. tropicalis is a hitherto unrecognized species. Radiating layers of yellowish or buff mycelium situated in the bark and cambium of the host are found to be constant and dis- tinctive characteristics of Endothia parasitica. None of the other species studied shows this character. * All species of the genus possess a stroma having a distinctive yellow to reddish color. There is no division of stroma into distinct layers, as described by some authors. Pycnidia or perithecia may arise in any portion of the stroma. Most commonly where pycnidia and perithecia are both present the pycnidia are above the perithecia, though the reverse arrangement is sometimes observed and all intermediate conditions frequently occur. The stromata of the species of section 1 are larger, more erumpent, and contain more numerous pycnidia than those of section 2. En- dothia singularis is especially striking in this respect. The stromata of section 2 are smaller and very similar in all the species. The pycnidia consist of more or less irregular chambers or locules in the stroma. The pycnospores are small in most species and furnish no very distinctive specific characters. The pycnospores of Endothia trop- icalis are, however, constantly larger and more variable in size than those of the other species. Paraphyses have been described by some authors, but have never been observed by the writers. The ascospores in the species of section 1 are very similar in size and shape. Those in section 2, though similar, have been found by thorough study and careful measurement to show constant though 76 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. slight differences, as indicated in the tables of measurements and ratios. Numerous cultures of all the species on a variety of media show that each species has constant and distinctive characters of growth and color. All the species grew equally well in light or darkness, and no de- cided differences in temperature relations have been demonstrated. The species appear to have well-defined geographic limits of distribution, which have been approximately determined for the American species. The distribution of the species does not coincide with that of the hosts, but seems to be determined in part by soil and climatic conditions. Endothia fluens has the widest distribution, being frequent and widely distributed in Europe and the eastern United States, and also occurring in Asia. Endothia parasitica is evidently of oriental origin. Specimens have been received from five rather widely separated localities in China and from two localities in Japan. In the eastern United States it is now abundant from Maine to North Carolina and is rapidly spreading south and west. It has already destroyed most of the chestnut trees within a radius of 100 miles of New York City. The species have rather definite host relations. Endothia gyrosa has been found on five genera of plants, viz, Cas- tanea, Fagus, Liquidambar, Quercus, and Vitis. Endothia singularis occurs, so far as known, only on Quercus species. Endothia -fluens has been found in America only on Castanea and Quercus, but in Europe it occurs on Alnus, Carpinus, Castanea, Corylus, Quercus, and Ulmus, and has been reported on Aesculus, Fagus, and Juglans. Endothia fluens mississippiensis has been found only on Castanea and Quercus. Endothia tropicalis is known only on Elaeocarpus. Endothia parasitica has been found on Acer, Carya, Castanea, Quercus, and Rhus, but at present is only known as a serious para- site on Castanea. Upon the American species of Castanea it is actively parasitic under all the conditions of soil and climate observed. Oriental species of chestnut are more or less resistant to the disease both in America and their native homes. None of the species except Endothia parasitica has thus far been found to be actively parasitic. LITERATURE CITED. (1) ANDERSON, P. J. 1914. Morphology and life history of the chestnut blight fungus. Com. Invest, and Control Chestnut Tree Blight Disease in Penn. Bui. 7, 44 p., 17 pi. 1913. (2) - and ANDERSON, H. W. 1912. The chestnut blight fungus and a related saprophyte. In Phyto- pathology, v. 2, no. 5, p. 204-210. (3) 1912. Endothia virginiana. In Phytopathology, v. 2, no. 6, p. 261-262. (4) 1913. The chestnut blight fungus and a related saprophyte. Penn. Chestnut Tree Blight Com. Bui. 4, 26 p., 6 fig. (5) and BABCOCK, D. C. 1913. Field studies on the dissemination and growth of the chestnut blight fungus. Penn. Chestnut Tree Blight Com. Bui. 3, 45 p., 14 pi. (6) and RANKIN, W. H. 1914. Endothia canker of chestnut. N. Y. Cornell Agr. Exp. Sta. Bui. 347, p. 531-618, fig. 77-101, pi. 36-40 (1 col.). Bibliography, p. 611-618. (7) BALLS, W. L. 1908. Temperature and growth. In Ann. 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AT 35 CENTS PER COPY UNIVERSITY OF ILLINOIS Agricultural Experiment Station URBANA, ILLINOIS, JUNE, 1916 BULLETIN No. 189— ABSTRACT PARASITIC RHIZOCTONIAS IN AMERICA' BY GEORGE L. PELTIER, ASSOCIATE IN FLORICULTURAL PATHOLOGY INTRODUCTION One of the most serious and troublesome diseases which must be contended with by carnation growers in this country is the so-called "stem rot" due to the fungus Rhizoctonia. In July, 1912, a study of this disease was undertaken by the writer, together with a thoro in- vestigation of those diseases of vegetable, field, and floricultural crops which are caused by Rhizoctonia, the primary object being to deter- mine whether infection is brought about by one or by more than one race or species of this fungus. DISTRIBUTION OF RHIZOCTONIA The fact that 165 species of plants are reported as being more or less susceptible to RJiizoctonia Solani Kiihn (Corticium vagum B. & C.) in the United States indicates the wide distribution of the fungus in this country. The writer himself has observed this fungus on seventy- five species, sixty-five of which were greenhouse plants. It is obvious that as long as investigations are continued the list of plants re- ported as susceptible cannot be regarded as complete or final. Plants belonging to the families AmarantJiacece, Caryophyllacece Cruciferce, Leguminosce, Solanacece, and Composite are especially susceptible. Under favorable conditions the fungus can attack plants in these families at any stage, when grown either in the field or in the greenhouse. About fifty important families of flowering plants are represented, several gymnosperms, and Equisetum, one of the Pteri- dophytes. The list includes a number of monocotyledons, which for- merly were reported as being non-susceptible to Rhizoctonia. Among the dicotyledons are many annuals and perennials, including herbs 'The complete edition of Bulletin 189, consisting of 112 pages, will be sent upon request. Address Director, Illinois Agricultural Experiment Station, Urbana, 2 and woody plants, as well as most of the greenhouse and garden plants, field crops, and weeds. R. Crocorum (Pers.) DC. has been reported so far in this country from only a few scattered states, on alfalfa and potato tubers. As investigations continue, however, this fungus will probably be found in many other localities. R. Solani ( C. vagum) has also been reported from Europe, Can- ada, the West Indies, South America, India, and Australia, so that it may be regarded as a truly cosmopolitan fungus. TYPES OF SYMPTOMS PRODUCED BY RHIZOCTONIA The symptoms produced by Rkizoctonia Solani (Corticium vagum) in natural infection are largely similar when appearing on the same type of host. The damping-off of seedlings and cuttings, of which Rhizoctonia is the most common cause both in the cutting bench and in the seed pan, is identical with the various plants, as is also the rotting of a number of root crops. In most herbaceous plants, such as the carnation, a stem rot is produced, the symptoms of which are identical on the various hosts. On very resistant plants, however, lesions only are formed ; these are apparently identical on the different hosts. INOCULATION EXPERIMENTS With the view of determining the degree of biologic specialization which may exist between the various cultural strains of Rhizoctonia, or between strains isolated from different hosts or of different geo- graphical origin, cross-inoculation experiments were conducted in- volving about 3,000 cuttings, 2,000 plants, and 7,000 seedlings of vari- ous kinds. With these, comparisons were made of about forty-five strains of Rhizoctonia, many of which were isolated by the writer. When carnation cuttings were infected, the strains used, with but two exceptions, whether from carnation or from other hosts, were able to cause more or less loss, the mortality of the cuttings ranging in either instance from 0 to 100 percent. Again, the same strains varied in virulence from one year to another, in most cases decreasing in viru- lence with age. When cuttings other than carnation were used, the results were the same. When young rooted carnation plants were inoculated, the percent- age of loss was much less than with cuttings. Here, however, the carnation strains seemed to be slightly more virulent than those from other sources, altho there was still a great difference in the strains from carnation themselves. Only one of the strains from other sources was unable to attack young rooted carnation plants. On old carnation plants in the greenhouse which were inoculated by contact, even the carnation strains did not cause a high percentage of infection. However, when plants growing under these same condi- 8 tions were slightly wounded and then inoculated, the percentage of loss was very high with nearly all the strains studied. When condi- tions (temperature and moisture) were favorable to the fungus, most of the strains studied were able to infect carnation plants as readily as the carnation strains themselves. In the majority of cases all strains were able to cause damping-off of various seedlings. There was a great difference in the virulence of strains when inoculated on the same host from which they had been isolated and when Inoculated on other hosts. Only occasionally was there any indication of marked specialization, and in no case was such indication corroborated in succeeding experiments. In older plants, a marked difference in susceptibility was found in the different species. As a rule, the root crops were highly susceptible. Herbaceous crops showed a very marked resistance, altho under cer- tain conditions they were quite susceptible. This variability of re- sistance held true for most of the vegetable and field crops other than root crops. Under ordinary conditions, the majority of flori cultural plants were not subject to attacks of Rhizoctonia, altho the mycelium of this fungus was known to be present in the soil or even on the plant itself. In a study of these experiments the point that stands out at first glance is the great variation in the mortality of the plants when inocu- lated with strains from the same host and when inoculated with strains from other sources. From the fact that all the strains studied showed the ability to attack the same species of plant and produce the same characteristic symptoms,. it seems clear that they can be in- cluded under one form, Rhizoctonia Solani Kiihn (Corticium vagum B. & C.). These experiments show further that the virulence of R. Solani ( C. vagum) is very variable, as is also the degree of resistance of the various host plants, both depending on a number of varying factors. GROWTH ON MEDIA Studies of the growth of Rhizoctonia Solani on media show that the strains are very variable, those from the same host often producing a different growth even on the same media, and that the differences in various cultural characters which are shown by strains from different hosts are no greater than differences which may be manifested by two different strains isolated from the same host or by the same strain at different ages. MEASUREMENT OF MYCELIAL CELLS Measurements of mycelial cells of various strains of RJiizoctonia Solani showed such variation, even with different strains from the same host, that on them, as 011 the growth on media, no conclusions can be based in regard to distinguishing the strains of this difficult species. SOIL SUEVEY By means of a local soil survey, it was found that Rhizoctonia So- lani (Corticium vagum) is abundant in sod and cultivated land with any crop, where it may live either on dead organic matter in the soil or on weeds and other plants. PARASITISM OF RHIZOCTONIA That Khizoctonia Solani (C. vagum) is an active parasite under certain conditions would never be (questioned by anyone who had seen a severe attack of carnation stem rot in the field or greenhouse. In the cutting bench this fungus causes damping-off of cuttings in an in- credibly short time, and of seedlings almost as quickly. At times Rhizoctonia causes considerable loss in potato fields. In fact, it may become epidemic and cause serious injury to most of the field, vege- table, and floricultural crops. The epidemics are apparently due to a combination of factors, such as the presence of a virulent strain of the fungus, a susceptible variety of plant, and optimum conditions of temperature and moisture for in- fection and development. Under ordinary conditions most of the strains appear to be weak parasites. The apparently universal presence of Rhizoctonia in the soil, where, under ordinary conditions, it can live indefinitely on dead or- ganic matter, makes it a dangerous fungus. The fact that it shows no marked specialization and can attack a large variety of weeds assists in the harboring of the fungus and in keeping up its virulence. The sclerotia and mycelium of Rhizectonia can live under adverse condi- tions for several years. In all but one of the experiments inoculation was brought about without wounding the plants in any way, in many cases the fungus be- ing simply mixed with the soil in which the plants were growing. The results furnish convincing proof of the parasitism of the fungus. The conditions under which all strains manifested their greatest para- sitism were primarily a high temperature (above 88° F.) and a mois- ture content of the soil either too low or too high for the best develop- ment of the plant. Repeated observations in the greenhouse and field have shown that a certain amount of the mycelium must be present before the fungus is able to attack and kill the plant. A small amount of mycelium has always been observed around a carnation plant in the bench a week or more before the plant showed any signs of being diseased. In fact, a certain amount of mycelium is always present in the carnation soil in the greenhouse, but it is only when the temperature is high that the fungus is able to attack the plants. This explains why stem rot of car- nations is more severe during the summer months than in the winter. In the field similar conditions are necessary to result in the infection of a plant. UNIVERSITY OF ILLINOIS Agricultural Experiment Station BULLETIN No. 189 PARASITIC RHIZOCTONIAS IN AMERICA BY GEOEGE L. PELTIEE UKBANA, ILLINOIS, JUNE, 1916 CONTENTS OF BULLETIN No. 189 PAGE Introduction 283 General Historical Account 283 General Characters of Ehizoctonia 286 Distribution of Ehizoctonia in the United States 292 Distribution of Rhizoctonia in Canada 306 Distribution of Rhizoctonia in South America and the West Indies 306 Distribution of Rhizoctonia in Europe 306 Distribution of Rhizoctonia in India and Australia 308 Plan of Procedure " 308 Symptoms of Rhizoctonia Disease on Various Hosts 308 Inoculation Experiments 337 Discussion of Inoculation Experiments 358 Growth on Media 364 Measurement of Mycelial Cells 370 Soil Survey of Rhizoctonia 372 Parasitism of EJiizoctonia Solani Kiihn 375 Summary 376 Appendix 378 Bibliography 386 FIG. 1. — CARNATION STEM ROT CAUSED BY Rhizoctonia Solani PARASITIC RHIZOCTONIAS IN AMERICA" BY GEORGE L. PELTIER, ASSOCIATE IN FLORICULTURAL PATHOLOGY INTRODUCTION One of the most serious and troublesome diseases which must be contended with by carnation growers in this country is the so-called "stem rot" due to the fungus Rhizoctonia. In 1911 a study of this disease was undertaken at the University of Illinois by Mr. H. W., Anderson, at that time Assistant in Floricultural Pathology and now' Professor of Botany in Wabash College. Since July, 1912, when Mr. Anderson left, a thoro investigation of those diseases of vegetable, field, and floricultural crops which are caused by Rhizoctonia has been conducted by the writer, the primary object being to determine whether infection is brought about by one or by more than one race or species of this fungus. The results of this phase of the work are pre- sented in the following pages. Extensive studies have also been made of stem rot, with a view to publishing at a later date. GENERAL HISTORICAL ACCOUNT The first description of Rhizoctonia was given by Duhamel,33 who in 1728 found it causing a disease of saffron (Crocus sativus) in southern France. The diseased bulbs were thickly covered with a reddish vio- let network of hyphaa which spread out into the surrounding soil, with knot-like swellings here and there in the mycelial network. Duhamel conceived these swellings (tubercules) to be the individual plants and the hyphse to be the roots, and named the fungus Tuberoides. Almost sixty years later (1785) another French investigator, Fou- geroux de Bondaroy,23 mentioned that asparagus that was grown on land in which diseased saffron bulbs had been previously grown suf- fered from this same disease. Bulliard11 in 1791 numbered it among the Truffles and named it Tuber parasiticum. Ten years afterward Per- soon82 placed the fungus in the genus Sclerotium and called it Sclero- tium Crocorum. De Candolle,24 who discovered a similar disease on lucerne, gave to the fungus the name Khizoctonia. Later he distinguished three species, /•*. Crocorum, R. Medicaginis, and R. Mali. Nees70 in 1817 referred "The results presented in this bulletin formed part of a thesis submitted by the author to the Graduate School of the University of Illinois in partial fulfil- ment of the requirements for the degree of doctor of philosophy in botany, May, 1915. Revised to date of issuance. 283 284 BULLETIN No. 189 [June, to a fungus attacking crocus as TJianatophytum Crocorum. This ap- pears, from his description and figures, to have been Rhizoctonia. A new species of Rhizoctonia was described in France by Duby20 as RJii- zoctonia Allii on Allium ascalonicum. In 1843 Leveille65 noted a simi- lar Rhizoctonia on Rubia tinctorum, Solanum tuberosum, Phaseolus, and Tulipa, without attempting to place it under any particular species. In 1851 the Tulasne brothers134 classified all the forms of Rhizoctonia as a single species, Rliizoctonia violacea, a classification which has been adopted by a number $>f writers. Rhizoctonia on cro- cus was reported in Germany in 1858 by Kuhn.64 He also found this same fungus, which he identified as R. Medicaginis, on sugar beet. At the same time he described a new species of Rhizoctonia on potato, which he clearly distinguished from the above species and to which he gave the name R. Solani. In the United States, Rhizoctonia was first reported by Webber137 in 1890 on the roots of alfalfa in Nebraska. He listed the fungus as Rliizoctonia Medicaginis DC. The first extended account of Rhizoc- tonia in the United States was given by Pammel,76 who found it caus- ing a serious disease of beets in Iowa. Later, Atkinson3 observed Rhizoctonia causing damping-off of cotton seedlings, and following that, of a number of other kinds of seedlings. In 1901 Duggar and Stewart32 added a large number of hosts subject to Rhizoctonia attack. Many observations of other hosts and in new localities have since been made until at the present time Rhizoctonia has been found on one or more hosts in practically every state in this country. It has also been reported from Canada, the West Indies, South America, India, and Australia, so that it may be regarded as a truly cosmopolitan fungus. Duggar," in an article published since this manuscript was com- pleted, brings out the fact that the violet root felt fungus, commonly known in Europe and the United States as R. violacea, should be re- ferred to as R. Crocorum (Pers.) DC. He states that unfortunately this name has priority over the more descriptive name R. violacea. Under R. Crocorum (Pers.) DC., Duggar lists the following pro- visional synonymy: Tuber parasiticum Bull. (1791) Sclerbtium Crocorum Pers. (1801) Ehizoctonia Crocorum DC. (1815) Ehizoctonia Medicaginis' DC. (1815) Thanatophytum Crocorum Nees (1816) Tuber Croci Duby (1830) Ehizoctonia Eubice Dene. (1837) Ehizoctonia Dauci Kabenh. (1859) Ehizoctonia violacea Tul. (1862) Ehizoctonia Asparagi Fckl. [non Fr.] (1869) Hypochnus violaceus Eriks. (1513) "Duggar, B. M. : Ehizoctonia Crocorum (Pers.) DC. and E. Solani Kuhn (Corticium vagum B. & C.) with Notes on Other Species. Ann. Mo. Bot. Gard., 2, 403-458, 9 figs., Sept., 1915. 19 16] PARASITIC RHIZOCTONIAS IN AMERICA 285 Under R. Solani Kiihn (Corticium vagum B. & C.), the form com- monly found in this country and to a less extent in Europe, and the name generally used by American authors, Duggar gives the following synonymy : BMzoctonia Betce Eidam [non Kiihn] (1887) Ehizoctonia Napcsce West. (1846) Ehizoctonia Rapce West. (1852) Hypochnus Solani Prill. & Del. (1891) Duggar states further that with the evidence at hand a number of species of Rhizoctonia described from Europe may be excluded from the genus, while several species are doubtful. He adds that in all probability the six species described from America, listed in Saccardo, may also be excluded, altho a more critical study of material is needed. Many attempts have been made to connect the sterile fungus Rhi- zoctonia with a perfect stage. Fuckel43 in 1869 stated that the ascomy- cete ByssotJiesium circinans Fkl. (LeptospJiceria circinans Sacc.) was the perfect form. However, beyond the association of these two forms on decaying stems of Medicago sativa, there were no signs of their con- nection. The same observation was also recorded by Prunet,90 but again with no more conclusive proof than the presence of the two forms on the same plant. Massee66 considered Rhizoctonia as representing the vegetative condition of Rosellinia, because of the fact that the struc- ture and color of the mycelium and the general habit of Rhizoctonia resembles that of the Rosellinia quercina Hartig and other destructive parasites belonging to that genus. He had no further evidence, how- ever, to support this supposition. During the summer of 1913, Cook,20 while examining tubers af- fected with Rhizoctonia, found a sclerotium that contained a mass of well-developed asci bearing spores. The mycelium of the sclerotium was characteristic of Rhizoctonia and the asci appeared to arise di- rectly from it ; this point, however, could not be determined with any degree of certainty. In 1891 Prillieux and Delacroix89 described a basidiomycete, Hy- pochnus Solani, and altho at the time they did not associate it with Rhizoctonia, it has been accepted by a number of European writers in recent years as the perfect stage of R. Solani. In 1897 Frank41 reported Rhizoctonia violacea as attacking grape- vines, and since a Thelephora was found associated with it, he pro- posed the name Thelephora Rhizoctonia?. In 1903 Rolfs,93 working with the Rhizoctonia disease of potatoes in Colorado, found constantly associated with this fungus a basidiomy- cete which Dr. E. A. Burt identified as Corticium vagum B. & C., var. Solani. He was able to trace the connection between the two forms, and completed his evidence when he obtained cultures of Rhizoctonia from single spores of the Corticium stage. 286 BULLETIN No. 189 [June, Eriksson38 has described a new combination, Hypoclinus viola- ceus (Till.) Eriks., which he believes is the perfect stage of Rhizoctonia violacea Tul. However, beyond association on different plants in the same field, he appears to have no further evidence to show that the perfect stage which he found on a number of weeds is connected with R. violacea, found on a number of root crops. GENERAL CHARACTERS OF RHIZOCTONIA • The morphological characters of RJiizoctonia Solani Kuhn. vary with the age of the mycelium. The young hyphas branch at an acute angle from the parent hypha, subsequently lying parallel to it. A constriction is shown at the point of union, and a septum is generally laid down a short distance from this point. The threads are colorless and vacuolate. With age the hyphae lie more at a right angle with the main axis, showing less constriction. They deepen in color into a yel- lowish and then a rather deep brown, becoming more or less granular and empty. (Fig. 2.) - Fusion of hyphae is very common and can be observed in any young culture of the fungus. It occurs either between hyphae of the same parent mycelium or between hyphae from separate colonies (Fig. 2). On many hosts a short tufted or bushy growth of the mycelium may occur with some strains. This tufted growth is likewise present FIG. 2. — (1) YOUNG HYPHAE OF Rhizoctonia Solani; (2) OLD, BROWN, AND EMPTY OF Rhizoctonia Solani 1916] PARASITIC RHIZOCTONIAS IN AMERICA 287 in cultures of the strains that produce such growth on the host plants. The tufts are composed of brown hyphae, closely septate, constricted at the septa, and often branching in an irregular manner. Sclerotia in cultures first appear as small, soft, white masses of hyphae. Later they become larger and turn dark and hard. Study of sclerotia at different ages shows that they are of uniform structure com- posed entirely of masses of irregular and barrel-shaped cells which break up into sections of one or several cells (Fig. 3). These shortened hyphal cells function as conidia and germinate readily under suitable conditions. Germination generally takes place by the protrusion of a tube thru the septum of a cell where it has broken away from an adja- cent cell. In some cases the hyphae of the germinating cells pass thru adjacent cells, which are apparently empty. Occasionally these irreg- ular and barrel-shaped cells germinate equatorially instead of at the poles. After the germ tube has grown out some distance, it becomes narrowed near the germinating cell and a septum is laid down. The mycelium then develops in the usual manner (Fig. 4). The formation of sclerotia in nature is rather common on many hosts. The best known examples are those formed on the potato tuber. The size and shape of the sclerotia vary considerably. On potatoes they are small, about 1 to 5 millimeters, and are generally flat. On carnation plants they may reach a diameter of 5 to 8 millimeters. When the fungus is grown on soil in pure culture, they become 5 to 6 centimeters in diameter (Fig. 5). The sporiferous stage of RJiizoctonia Solani was first observed in this country by Rolfs93 in 1903, on potato stems. It was described by Hurt 94 as Corticium vagum B. & C., var. Solani* In Europe this same fungus is generally known as Hypochnus Solani Prill. & Del." Altho the writer has observed RJiizoctonia Solani on seventy-five species of plants, including weeds and field, vegetable, ornamental, and floricultural crops, growing under diverse conditions and at different times of the year, for the past three seasons, it was not until the spring of 1915 that he found the Corticium stage. It was then observed in his home garden on bean, beet, radish, potato, parsnip, carrot, chard, spinach, pea, plantain, and pigweed. This stage was also found on winter vetch growing on newly plowed land, on carnation plants, and on a number of annual and perennial plants. In some cases patches of soil well protected from desiccation were covered with the ashy gray mycelium of the perfect stage. "In a recent letter from Dr. Burt, he states : " I do not now believe that there is even a varietal difference between Corticium vagum B. & C. and that on the potatoes; hence I shall drop var. Solani." bln his monograph on the Thelephoracece, Burt12 limits Hypochnus to resupi- nate species with colored, echinulate spores, while under Corticium he includes species always resupinate, which have colorless spores and lack cystidia. Accord- ing to Burt's classification, Hypochnus Solani Prill. & Del. becomes a synonym under Corticium vagum B. & C. 288 BULLETIN No. 189 [June, Fi«. 3. — (1) YOUNG, BARREL-SHAPED CELLS WHICH COMPOSE THE SCLEROTIA OF Ehizoctonia Solani -, (2) OLDER, EMPTY CELLS FROM THE SCLEROTIA FIG. 4. — GERMINATING SCLEROTIAL CELLS OF Rhizoctonia Solani PARASITIC RHIZOCTONIAS IN AMERICA 289 & 290 BULLETIN No. 189 [June, The presence of the Corticium stage seems to depend on climatic conditions. A cool season with an abundance of moisture is appar- ently essential for its development in the field. This stage is gener- ally found on plant tissues that are perfectly healthy ; it is in no way injurious to them. Some cases have been found where it had devel- oped on stems almost cut off by Rhizoctonia, but in no instance has the writer seen it form directly on a lesion or on injured tissue. (Sec Figs. 6 and 7.) The development of the Corticium stage may be described as fol- lows : The dark brown hyphae of the sterile stage gather, usually at the base of the plant, and from them arises an ashy gray mycelium, which forms a fine network around the stem. The development is usually faster where a little soil, thrown up by the rains, has formed a film around the stem. The extent of this fruiting layer varies, but it may proceed several centimeters up the stem. It is so lightly attached to the plant that it may easily be rubbed off. As it becomes old, it cracks and falls off. The outer hyphae of the fruiting layer bear club-shaped basidia with four sterigmata and spores. Cystidia are lacking. The spores are colorless, oval to ovate, and have pointed bases. The usual spore measurement varies from 9 to 14 /x by 6 to 8 p. Cultures of Rhizoctonia from single spores of the Corticium stage have been obtained both by dilution methods and by the method used by Rolfs,94 which consists in placing a stem covered with the fruiting stage over an open petri dish containing a nutrient agar, and allowing the spores to drop on the agar. Another fungus belonging to the genus Corticium, C. oclira- Icucum (Noack) Burt (see footnote b, page 287), found in the United States by Stevens and Hall117'119 011 pomaceous fruits, has been care- fully examined by the writer. The mycelium of this species corre- sponds in many respects to that of R. Solani and the development of the perfect stage is similar to the development of the Corticium stage of that species. It appears that these two species are very closely re- lated, but are entirely distinct forms. Duggar,a wrho has had an opportunity to study R. Crocorum (Pers.) DC. more at length, gives the following description of this species in his recent work : "The external, general hyphae are more or less different in form and appear- ance with age. The younger hyphae are usually dilutely violaceous with a pigment which may be decolorized by the application of acidulated water. The protoplasm is dense towards the tips of branches and vacuolated farther away. The hyphae are somewhat flexuous, branched (sometimes closely), with the branches arising at right angles to the main hypha, and with a partition wall laid down at not over 10 p. distant. With age the hyphae become rigid, somewhat less in diameter, 4-8 fji, the branching is distant, and these branches readily break off at the first partition wall. At the point of union the diameter is uniform with the main •See footnote, page 284. 1916] PARASITIC KHIZOCTONIAS IN AMERICA 291 FIG. 6. — GREEN TOMATO SHOWING THE SUPERFICIAL ASHY GRAY MYCELIUM OF Cor- ticium vagum B. & C. PRESENT AT THE POINT WHERE THE TOMATO TOUCHED THE SOIL FIG. 7. ENLARGED VIEW OF A SECTION OF FIG. 6, SHOWING THE DARK STRANDS OF HYPH.E AND SMALL, SPHERICAL, BROWNISH SCLEROTIA OF Rhizoctonia Solani KUHN WITH THE ASHY GRAY NETWORK OF MYCELIUM OF Corticium vagum B. & C. (5x) 292 BULLETIN No. 189 [June. hypha. The partition walls are distant, often 120-200 //, apart. The walls now possess the violet -brown pigment and in the lumen little or no protoplasm is ob- servable. ''The internal mycelium is likewise branched, septate, often associated into loose strands, passing between the cells or traversing them. In the early stages of the disease, so far as reported, these internal hypha} are nearly colorless and are generally of less diameter than those constituting the external mat. " the hyphae constituting the external mantle may be uniformly dis- tributed, as is the case usually when the fungus attacks fleshy roots or tubers, or they may also form a number of aggregates having the appearance of loose or root- like strands." The infection cushions are distributed^ over infected roots. ' ' The external hyphae are for the most part similar to those of the general mycelium, but there occur also branches in which the cells are short and swollen, sometimes resembling a short chain of spores The medullary portion of younger cushions is made up of finer, almost colorless hyphae, and it is this type which enters — strand- like — the cortical tissues of the root, destroying particularly the cambium and younger phloem regions. In the later stages of development it will be found that the cushions seem to extend considerably into the cortex, and more of the hyphae are colored." ' ' The true sclerotia are flattened or rounded bodies varying in diameter from a few millimeters to several centimeters. When mature they are of a deep violet- brown and are thickly clothed with a persistent velvety felt, externally of the same color as the root-investing hyphae, but darkening further in. Among the surface hyphae of the sclerotia as well as of the 'infection cushions' are found chains of enlarged cells quite distinct from the enlarged cells of R. Solani. The sclerotia, as noted previously, are always connected with the root felt by large hyphal strands. tf a sclerotium consists of fairly compact tissue made up of cells often considerably branched and sometimes curiously lobed. " DISTRIBUTION OF RHIZOCTONIA IN THE UNITED STATES In Table 1 is presented a list of those species and sub-species which have been reported as being susceptible to R. Solani in the United States. It is obvious that as long as investigations on this dis- ease are continued, such a list cannot be regarded as complete or final. It may be noted that plants belonging to the families Amaranfhacece, Caryophyllacece, Cruciferce, Leguminosce, Solanacece, and Composite are especially susceptible to this .fungus. Under favorable conditions it can attack plants in these families at any stage, from seedlings or cuttings to older plants, when grown either in the field or in the green- house. About fifty important families of flowering plants are repre- sented, several gymnosperms, and Equisetum, one of the Pterido- phytes. The list includes a number of monocotyledons, which for- merly were reported as being not susceptible to Rhizoctonia. Among the dicotyledons are many annuals and perennials, including herbs and woody plants, as well as most of the greenhouse and garden plants, field crops, and weeds. R. Crocorum, as will be seen in Table la, has been reported so far in this country from only a few scattered states. It is probable that as investigations continue this fungus will be found in many other localities. 1916] PARASITIC BHIZOCTONIAS IN AMERICA 293 bo a BH~ 03 &JD CJD -»J O ~> o O S M I io g § 1= at 1 o 2 — I r- IT— IT— li— lOrHi— IO»— loOr- IT— IOr- IT— IO»HOOO Oi Oi O^ O^ Oi O^ Oi Oi O} Oi Oi O^ o^ OS Oi Oi Oi OS OS O5 OS O5 OS OS OS OS OS OS OS OS OS OS OS -^ M S-l _ >H o o >H 2 ^ 2 K* 'o g'o ^ .9 ,2 .9 ^ ^ 1 io o.2 .2 ;i! 1 5 I- c3 >« si IF 15 gJ S "e rO § ^^ yl -^ ^ sob *"poa«» * ::::: • : :> 1 = s« §| J it C-4 ' ^J : ^r - bo PH i! :« ^P,^ - • • I • !"S !ii: ?- 7-r> ^ 2 ?! -I p: .Is S rt fe ,U^^: : : : : : * • Tfl H ^ O .§ * Q- - ifi " fil£. a^s 1 ^«s^^ ^llllS. :;|||1I: ^^^^^ ^ S^ ^ o iir ;|| «s ?f"l =o os • -^ &LS £ C ^ <3i g •S .§ S. f = "8," - - ^ - - Illi 55 l^§^s I S =o 02 3 »-*1 o 294 BULLETIN No. 189 [Jane, la 09 CU -g g ocd s .s H a g ^03 QC-P -.i., 003 MP ^-2fl^SFo^3sc3^ S^g- r^lj^^^s ocS^^1--^lTJoSrO^HO-rr5^ a2^c»pHQc» HoQPQcC'^P MPH0205OWHJQHWMOPH 1 ?HiHrHi-lrHrHr-li-lrHi— li-Hr-l^rHr-lT-li— IrHi-l QQ o'o® 1916] PARASITIC EHIZOCTONIAS IN AMERICA 295 ld) » t S ,ort 22QP3Q QQ GC i f S s ccP Decaying stem Eoot rot field Dujjgar and Stewa Wolf* Pelti OD 0> M —* M &>2 " • D K S iC bCr^ be SB 53^ S7S 3 « 02 K W Q 02 ft W O^i^rHTHrHrHiHiHrHi^Or^rHrHrHrHrHO Oi O^ Oi Oi Oi Oi Oi Oi Ci Oi Oi Oi Oi Oi Oi Oi Oi O^ Oi Ci Oi Oi Oi Oi Oi Oi Oi Oi Oi O^ Oi Oi O^ Oi M *ts 613- " 296 BULLETIN No. 189 [June, 5~3 8 « & 60 - o -o p ,3- I So « M 0 1 II: h- S: .2 a |: as •» y O V_X Q' bC-M bO o 2 fl o PHCQ OGQ 02 02 Q 02 P 02 5 5 a o^ « rt > pa® op 0.53®^ W 0 PH Pn P M W O PM >-3 ^ ill * ^ 0313 a •73 •gf 111: eso arol tn ~ > "* i— < -i-i o cs o ~ (73 Q tf> Q Cfc O3 •s w •* £ ^-* $4- ^5H- ^So S 50- bC 4-> bjo -*a S- bo oaP fi eS* '^" 02 P P M >H (H §§ flt ^ 1 ^^ 5»| g S|fe ^ § S 53 39 O 0) -fH i— I i— IJOOiCiCiOi rHOOr- liHOi-H 03 ^ .5 ^ "oj 00 03 • ^ 03 .O 9 ^ .OJ ' ? .2 &H HH ill 1 298 BULLETIN No. 189 [June, •S bo 9 *P< 4* H O CO W P M S-S g02 02 n=J •3 > * fl * co Oi o co oa CQ 0 O r-l rH i— I T-H 01 Oi Oi O^ O5 O^ 02 1916} PARASITIC KHIZOCTONIAS IN AMERICA 299 300 BULLETIN No. 180 be a a •" seedlings O bc^, be 02 W M r£ "CD „ : : : : S^ o o -Jf be „ s. . . . 2.2 PH " PJ^ •»•>•» P^ 111 I I 3Pn O »2Q a wo* tg^- CH -2 'oQj" ^3 «W K^ dlilff: ^WopqW^ c.2 ^~ - ,2 « :|1 «8 S P^ s-a o > Co M CH O fe^ ll^ (^ «n .3 2 2 -2 ^ 03 o s M « pi M o s-g « 03 I 1916] PARASITIC RHIZOCTONIAS IN AMERICA 301 2 'QJ «d V.8 2 « §45 ^5 PH g O £S - QCC O E3 •a. ~|, 2 $- 2 §~ eg *H ® O> ^~" bo e « « g g 9 29 8 S •!- : ^JU S pq pq p oq f§ H 03 •45 S II So «? ^ s s .2 " .2 "s S" S'S S O s_x o fcC -4-a 5JJD OQ 02^ ^HsQQpM C5PB pnPPHHsPH T-H-r+irafMm-^ti'rfl-rfli— iTtt-rtli— l ro ffM ^« • T* rH CO (M rt< TP Oi O^ Oi Oi Oi Oi Oi Oi Oi Oi Oi O^ Oi Oi OS Oi s ^ .a a > « > " •« -< *« •» " •> •> • 5 - ~ * - » - - £ 7. ^ ^ ^ ^ ^ ^ ^ C5 1 4 : 5 », ^ $ .S 'c 1 « - 4 !3 1 P= <5J a c LI ? t£ .'s > •> ts « s »,s •^••^ c "^20 M rO S « r2 *~ ?3s S O 1916] PARASITIC RHIZOCTONIAS IN AMERICA 305 S> II I O ^~^ bJO 02 |1 II si II . ® 5 ® a j5k< Q g ' a * 3! be |: & i 1 306 BULLETIN No. 189 [June, DISTRIBUTION OF RHIZOCTONIA IN CANADA In a letter to the writer, Dr. H. T. Giissow of the Central Experi- mental Farm, Ottawa, Canada, stated that he had observed Rhi- zoctonia Solani on potato, pea, sweet pea, and aster. That the stem rot of carnation also occurs in Canada is shown in a paper read by John Morgan of Hamilton, Ontario, before the Canadian Horticul- tural Association at Guelph, in August, 1906. DISTRIBUTION OF RHIZOCTONf A IN SOUTH AMERICA AND THE WEST INDIES The following list of plants reported as susceptible to R. Solani in South America and the West Indies, with character of injury, has been compiled from Cook's19 Diseases of Tropical Plants: Bean Damping-off, dry rot of stem, and pod rot Beet Boot disease Cotton Damping-off and sore shin Cucumber Damping-off Lettuce Damping-off Melon Damping-off Nursery stock Damping-off Pea Boot and stem rot Potato On stem and tubers Seedlings Damping-off Sweet potato Boot rot Tobacco Seed-bed rot Tomato Rosette and fruit rot DISTRIBUTION OF RHIZOCTONIA IN EUROPE Despite the wide distribution of Rhizoctonia in Europe, the nomen- clature of the species is in a very confused state. Some writers under- stand Rhizoctonia Crocorum (Pers.) DC. to include several species, while others treat it as a separate species including forms with a rich violet mycelium. This uncertainty extends to the other common species of Rhizoctonia, so that the European literature on the subject offers many difficulties. Another fact which adds to the confusion is that both Rhizoctonia Solani and Rhizoctonia Crocorum attack potato stems and tubers, and while the symptoms caused by the two fungi can be easily distinguished from one another in the field, it is another mat- ter to differentiate between them in literature. A partial list of the hosts in Europe which are attacked by Rhizoc- tonia is given below to show the extent of the distribution of this fun- gus. Only the more important references are mentioned. Austria Hungary. — Rhizoctonia was first reported in Austria Hun- gary in 1875 on potato. Later R. Crocorum was found on sugar beet, potato and lucerne, and R. Solani (Corticium vagum), on potato. 1916] PARASITIC RIIIZOCTONIAS IN AMERICA 307 Belgium. — R. Crocorum has been observed in Belgium on sugar beet, potato, and asparagus. Denmark.— Ei. Rostrup,90'97 during the years 1884-1905, reported Rhizoctonia in Denmark on a large number of hosts, including many weeds and the roots of several species of forest trees. Among the cultivated crops mentioned are carrot, clover, lucerne, kohl-rabi, beet, turnip, sugar beet, and potato. Both R. Solani and R. Crocorum were observed on the potato. In 1892 Rostrup described a new species from turnip, which he called Rliizoctonia fusca and which differed only in one or two essential characters from R. Crocorum, also found on turnip. England. — Rhizoctonia was first reported in England on mangel in 1901, and on potato in 1904. The next year Giissow,48 in an ex- tended account of this disease, stated that it was due to R. Solani. Salmon,101 in working on a disease of seakale due to R. Crocorum , found that it was also able to attack salsify, parsnip, carrot, parsley, lettuce, and potato. Finland. — Reuter91 has studied a Rhizoctonia in Finland which causes a root rot of rye. R. Crocorum has been found on beet. France. — Between the discovery of R. Crocorum in France in 1728, on crocus, and 1851, a number of hosts, including asparagus, bean, clover, Citrus, Coronilla, grape, onion, Rubia, Sambucus, and tulip, were reported. Germany. — In 1858 Kuhn64 found R. Crocorum on sugar beet in Germany and described the species R. Solani on potato and carrot. Eriksson38 states that in Germany in 1893 R. Crocorum appeared on sugar beet in several places ; on lucerne, in 55 localities on plants 1 to 5 years old ; on potato, in 11 localities ; on asparagus, in 3 locali- ties ; on hop, in 1 locality ; and also on a f ew weeds, such as Taraxacum officinale, Convolvulus arvensis, etc. ; and that in 1894 it was observed on lucerne, in 77 localities; on potato, in 11 localities; and on red clover, in 8 localities. The species R. Solani (Corticium vagum) and R. Strobi Scholtz on white pine, have beeru recorded. Holland. — Dr. Johanna Westerdijk reports both R. Crocorum and R. Solani as being very abundant on potato in Holland. Ireland. — Pethybridge 83'55 has shown that both R. Crocorum and R. Solani are present on potato in Ireland. Italy. — R. Crocorum has been reported at various times as present on alfalfa, sugar beet, clover, asparagus, carrot, parsley, chard, the roots of grape, and many weeds in Italy. Rhizoctonia destruens Tassi occurs on the roots of Delphinium. Portugal. — The Rhizoctonia attacking sugar beet has been reported from two localities in Portugal. Russia. — R. Solani was reported on potato in Russia in 1899. 308 BULLETIN No. 189 [June, Sweden. — Eriksson37'39 observed a disease of carrot and beet in 1898 in Sweden, caused by R. Crocorum. He was able to inoculate this fungus on garden and sugar beet,^ alfalfa, potato, and many weeds — Stellaria media, Myostis arvensis,' Galeopsis, Titrahit, Erysimum clieiranthoides, Urtica dioica, and Sonchus sp. In addition to these hosts Eriksson has reported R. Solani (Corticium vagum) on potato and R. Crocorum on turnip and kohl-rabi. DISTRIBUTION OF RHIZOCTONIA IN INDIA AND AUSTRALIA Shaw,109 working on the morphology and parasitism of Rhizoctonia in India, reported RJiizoctonia Solani on peanut (Arachis Jiypogoea), cowpea (Vigna catjang), jute (Corchorus capsularis), Dolichos Lab- lab, Trichosanthes cucumernia, soybean (Glycine soja), mulberry (Morus alba), sesame, melon roots, cotton, roots of Agave rigida, and potato. In Australia, McAlpine67 found R. Solani very widely distributed on potato. PLAN OF PROCEDURE The main object of the present research was to determine whether of the culturable forms of Rhizoctonia one or more than one race or species. is present in this country. The work was taken up from the following standpoints : 1. Symptoms of Khizoctonia disease on various hosts 2. InocuJation experiments 3. Growth on media 4. Measurement of mycelial cells 5. Soil survey SYMPTOMS OF RHIZOCTONIA DISEASE ON VARIOUS HOSTS Following are presented the observations of the writer concerning the nature of the diseases caused by Rhizoctonia on the various hosts, together with the principal facts which appear in literature regarding Rhizoctonia on the more important crop plants in this country. ALFALFA, Medicago sativa On March 17, 1914, the attention of the author was called to the damping-off of young alfalfa seedlings in the agronomy greenhouse of the Station. Microscopic examination and pure cultures showed it to be due to Rhizoctonia. The seeds had been sown in rows in pure quartz sand and kept well moistened. The young seedlings, on ger- mination, were somewhat crowded, so that the conditions were very PARASITIC BHIZOCTONIAS IN AMERICA 309 favorable for damping-off. The fungus could be seen extending in all directions over the surface of the sand. The fungus found on the diseased alfalfa seedlings was compared with a fungus obtained from mature alfalfa plants sent from Iowa. Altho the mycelium of the two forms was characteristic of Rhizoctonia, it differed in many respects, particularly in the color of the hyphse. The form on the mature plants was undoubtedly Rhizoctonia Cro- corum, while that on the seedlings was the common Rhizoctonia Solani. Rhizoctonia was first reported on the roots of alfalfa from Nebraska in 1890, by Webber,137 as Rhizoctonia Medicaginis DC. This fungus was next mentioned on alfalfa as Rhizoctonia violacea, by Heald,57 who found it causing a root rot in a single locality in Nebraska in 1906. In 1908 it was reported by Freeman,42 under the name Rhizoc- tonia violacea, as spreading rapidly in the alfalfa fields in Kansas. Freeman described the disease as beginning in different parts of the field where at first a single plant dies. From these centers of infec- tion the fungus grows in all directions thru the soil, killing the plants as it proceeds. Thus circles of steadily increasing radii are formed, at the edges of which plants in all stages of the disease are found. The great majority of the plants within the affected areas die, while those which survive are not vigorous and always lose their main tap roots. The first external sign of the disease is a yellowing of the plant, which soon after wilts and dies. The roots of a dead or dying plant are found to be covered with a violet or brownish red mat of mycelial strands, or hyphse. In a few cases the tap root is completely rotted. In less severely affected plants, the cortex of the roots slips off easily when the plants are lifted from the soil, leaving only the central woody cylinder. This condition is due to the fungous threads which grow thru the cortex as far as the cambium layer, which they kill. The fungus forms sclerotia, which may live in the soil for several years. Stewart126 in 1908 mentioned a root rot and damping-off of alfalfa in the field in New York. His description of the disease1 agrees in some respects with the one given by Freeman. Later he also noticed the damping-off of alfalfa seedlings in the greenhouse. He was not certain that Rhizoctonia Crocorum was present in New York, and was of the opinion that the fungus causing the damping-off of seedlings in the greenhouse was different from the one found in the field. Heald,58 in a later article (1911), described more fully the disease occurring in Nebraska. At that time he regarded the fungus as iden- tical with Rhizoctonia Medicaginis DC. of Europe. From the above accounts it is certain that there are two species of Rhizoctonia in this country able to attack alfalfa— R. Solani, widely distributed, causing only a damping-off of seedlings, and R. Crocorum, with a limited distribution, attacking as a rule only mature plants in the field. At present this latter species has been reported on alfalfa from Nebraska, Kansas, Iowa, and Virginia. 310 BULLETIN No. 189 [June, ALTERNANTHERA, Telanfhera sp. In the fall of 1912 cuttings from alternanthera, coleus, and salvia plants which had been placed in the same bench were found to be damping-off. A microscopic observation and pure cultures from dis- eased cuttings showed that Rhizoctonia Solani was the causal organism. Later the fungus was found on alternanthera plants in the field, but apparently it caused no injury there. Alternanthera plants grow low and bushy, and thruout the sum- mer, no matter how dry the season* the soil underneath is usually moist. On close examination of the tangled mass of branches, strands of a fungus, which were later found to be made up of bundles of hyphae, could be seen spreading in all directions. At first glance the masses of mycelium looked very much like old spider webs. A number of different varieties of alternanthera were examined, and all were found to have the characteristic brown strands ramifying upon the surface of the whole under side of the plant. The reddish varieties seemed to have more of the fungous strands than did the green and variegated plants. Cultures from the brown strands in every case yielded pure cultures of Rhizoctonia which corresponded morphologi- cally and physiologically to the Rhizoctonia obtained from the cut- tings. Whether the fungus was at any time parasitic on the plants in the field was questionable. However, cuttings made from them still con- tained pieces of mycelium, and when placed in sand in the greenhouse, the fungus did parasitize not only the alternanthera cuttings but others as well. The belief that Rhizoctonia is present on the branches of the alter- nanthera plant thruout the year was corroborated in 1913 and again in the fall of 1914, when the cuttings made from plants in the field began to damp off in the cutting bench. Repeated observations showed that the fungus was present on the plants in the field, notwithstanding the fact that they had been planted in new soil. Old plants brought in from the field were cut close to the roots and planted in flats in the greenhouse. These sprouted and developed new shoots, from which cuttings were made. Many weeds came up in the flats during the win- ter, and in March both the cuttings and the weeds became infected with Rhizoctonia. It seems, therefore, that the fungus is present on alternanthera at all times of the year, tho the only injury it causes is damping-off of cuttings in the greenhouse. ALYSSUM, SWEET, Alyssum odoratum During June, 1914, when the bedding and decorative plants were being set out from the floricultural greenhouses of the Station, about PARASITIC RHIZOCTONIAS IN AMERICA 311 twenty-five plants of sweet alyssum growing in two and one-half inch pots were found to be diseased. The plants were tall and had fallen over from their own weight, so that they formed a mat over the pots. On close examination the soil and plants were found to be covered with the strands of brown mycelium which are characteristic of 7?. Solani. A number of these plants died, while on the stems of others the fungus formed small lesions near the surface of the soil. The fun- gus continued to grow 011 diseased plants placed in the field, and killed a few more of them. AMARANTHUS Specimens of Rhizoctonia on Amarantlms retroflexus were received from Mr. W. H. Burkholder of Cornell University. The mycelium of the Corticium stage could be easily recognized on the stems, while the Rhizoctonia stage was plentiful on the lower part of the plant. A cul- ture was obtained from scrapings made from the mycelium of the Cor- ticium stage. Several spores Avere found and one basidium showing the four sterigmata was observed. Duggar and Stewart32 reported the occurrence of Rhizoctonia on Amaranfhus retroflexus (pigweed) and A. albus (tumble-weed) in New York in 1901. Several years later Rolfs95 found the perfect stage, Corticium vayum, in Florida on A. retroflexus and A. spinosus. ASPARAGUS, ORNAMENTAL, Asparagus sprengeri Duggar and Stewart32 observed the effects of Rhizoctonia on a number of plants of ornamental asparagus. They found that the plants were killed and that many of the leaves were bound to each other by the brown threads of the Rhizoctonia hyphag. ASTER, CHINA, Callisteplms liortensis Damping-off of aster seedlings was noticed in flats in the floricul- tural greenhouses in the spring of 1913 and again in 1914. The dis- ease first appeared as a small, brown spot on one side of the seedling at the surface of the soil. This lesion increased in size until the seed- ling fell over. After a number of seedlings were prostrated, the fun- gus spread over them, and in time a mat of mycelium covered the sur- face of the soil. In May, 1914, a number of aster plants, four to five inches high, were planted in old soil in which several varieties of carnation plants had been growing during the winter. There had been more or less stem rot among these plants all the season. After a month, when the aster plants were about 6 inches high, they began dying off and con- tinued to die until they were from 9 to 12 inches high and ready to 312 BULLETIN No. 189 [June, bud. Other aster plants set in new soil at the same time that these were transplanted developed normally with no stem rot whatever. TABLE 2. — MORTALITY OF DIFFERENT VARIETIES OF ASTER GROWN IN OLD CARNA- TION SOIL INFECTED WITH Rhizoctonia Solani Variety Number of plants Total dead Total healthy Queen of the Market 50 1 49 Lavender * 50 1 49 Azure Blue 50 4 46 Purple 50 7 43 Pure White 100 13 87 Shell Pink 50 2 48 Kose Pink 50 0 50 Deep Rose 50 0 50 Crimson . . 50 1 49 As can be seen from Table 2, plants from all but two of the varie- ties died in the bench. The varieties Azure Blue, Purple, and Pure White were planted where most of the stem rot on the carnations oc- curred ; hence the higher number of diseased plants in those varieties is due to location rather than to varietal susceptibility to Rhizoctonia. Obviously the Rhizoctonia causing carnation stem rot was in this case able to attack healthy aster plants. The stem rot of these plants was typical and very similar to the rot of carnations. The first sign of the disease was a yellowing and drooping of the foliage, followed, sooner or later, depending on weather conditions, by a sudden wilt- ing of the whole plant. When the plant was pulled, the bark of the stem near the surface of the soil would slough off, leaving only the dis- colored woody tissues. A stem rot of aster due to Rhizoctonia has been reported only once before in this country. Duggar and Stewart32 in 1901 found the my- celium in the tissues of aster and later isolated a pure culture from them. They observed the disease in a number of localities in New York during that summer. BEAN, PJiaseolus vulgaris The damping-off of young bean seedlings by 7?. Solani, which has been observed in the greenhouse and in the field, is characterized by the production of small lesions at the surface of the ground either on one side of the stem or girdling it, followed by the falling over and death of the seedling. When the fungus attacks older bean plants, lesions of various sizes are produced just below the surface of the ground, at the surface, or one or two inches above it. In some plants these discolored spots can be found on the larger roots also. The lesions, as a rule, have a 1916] PARASITIC RHIZOCTONIAS IN AMERICA 313 FIG. 8. — STEMS OP MATURE BEAN PLANTS WHICH HAD BEEN PLACED IN A BENCH INFECTED WITH Rhizoctonia Solani ORIGINALLY OBTAINED FROM CARNATION PLANTS reddish brown band with a lighter colored, sunken area, and extend thru the cortical layer into the woody tissues. As on the young seed- lings, the spots are usually localized on one side of the stem, but in some cases one lesion may girdle the plant. These lesions weaken the stem and cause it to break off easily. The first account of Ehizoctonia causing a disease of bean was given by Atkinson.4 He reported that during the winter of 1894-95 it caused damping-off of bean seedlings and attacked plants that were from 6 to 10 inches high. He referred to this form as ''the sterile fungus," and stated that its most characteristic peculiarity was the mode of branching. In 1901 Duggar and Stewart32 reported this fungus, from New York, as the cause of a stem-rot disease of red kidney beans in the field and of a damping-off among seedling beans in the greenhouse. 314 BULLETIN No. 189 \June, In 1904 Hedgcock00 reported as follows : "The bean crop in the vicinity of St. Louis was severely injured by a Khi- zoctonia which attacked the stems and large roots of the plant and also produced brown sunken areas on the surface of the pods, penetrating the latter and discolor- ing the seeds. An examination of a number of seeds whose surface was discolored, disclosed the fact that the mycelium of the fungus had established itself in the second coat and in many instances had formed minute sclerotia there without rot- ting the seed or even penetrating the cotyledons. The presence of the fungus did not prevent the germination of the seed." Fulton44 in 1908 showed that Rhizoctonia from infected pods caused damping-off of seedling beans and of month-old plants. A serious outbreak of the stem rot of beans was reported from New York by Barrus9 in 1910. He found that in some fields as many as 30 percent of the plants were infected. In the same fields during the following season it caused the death of at least 5 to 6 percent of the seedlings; later in the season, after a rainy spell, a large percentage of the pods in contact with the ground became infected. BEET, Beta vulgaris Young seedlings of the garden beet, in flats, were found damping off in the vegetable-gardening greenhouses of the Station, July 10, 1913. Cultures showed that K. Solani was the sole cause of the dis- ease. Characteristic lesions were found on the beets at the surface of the ground, and strands of mycelium could be plainly seen spreading out on the surface of the soil. As with root rot of other fleshy crops, the fungus gains its first held at the crown of the mature plant, which, as a rule, is just below the surface of the ground. The first evidence of the disease is a darkening of the leaf bases, followed by the rotting of the crown. The leaves retain their color for a long time, or until the leaf stalks rot off almost completely. With the rotting at the crown, the beets begin to crack from this point. While the tissues around the cracks remain firm, as a rule, for a long time, the crown is usually soft, a condition due to the entrance of other organisms. Lesions are some- times formed on the sides of the beets, often extending deep into the tissues. When weather conditions become unfavorable to the fungus, the rotting and cracking stops and the plant may recover from the attack. The disease is generally scattered thru the field, only a few plants in a given area being affected. Under the name Rhizoctonia betce Kiihn, Pammel76 in 1891 de- scribed a root rot of sugar beets. He was the first investigator to re- port serious damage caused by Rhizoctonia in this country. Duggar28 in 1899 regarded the root-rot disease of sugar beet due to Rhizoctonia as one of the important diseases of that plant. At the present time this disease is very widespread and is the cause of considerable loss, especially in irrigated regions. PARASITIC RHIZOCTONIAS tN AMERICA 315 FIG. 9. — GARDEN BEET INOCULATED WITH Rhizoctonia Solani FROM CARNATION, SHOWING A LATE STAGE OF INFECTION (Experiment 8) Damping-off of sugar-beet seedlings has been reported by Selby,108 from Ohio, and by Smith,113 from California. BEGONIA Mr. H. W. Anderson in 1911 found a number of begonia cuttings in the floricultural greenhouses that were damping off badly because oif Rhizoctonia infection. The symptoms were similar to those described for cuttings of alternanthera. Damping-off of begonia cuttings has also been observed in New York by Duggar and Stewart,32 and in North Carolina by Stevens and Wilson.122 BLACKBERRY, Rubus sp. Root disease of blackberry and raspberry caused by Rhizoctonia has been reported only once in this country. Paddock 70 of Colorado, who studied this disease, described it as follows: ' ' The trouble was first noticed by the foliage becoming light green or yellow- ish. Later in the season leaves on occasional plants began to curl and shrivel as parts of the plant beloAV ground were attacked, but the greatest injury occurred on the canes above the crown. Here the bark was discolored and shrunken from the crown to the surface of the soil, or a short distance above. The fungus grew out within the bark, destroying the tissues, and interfering with the movements of plant food. The injury commonly extended around the cane, and when it became deep enough to cut off the supply of moisture and food, the plant died. ' ' BUCKWHEAT, Fagopyrum esculentum In 1911 Stevens and Wilson120'121 mentioned a serious outbreak of Rhizoctonia on buckwheat in the western part of North Carolina. No description of the disease was given. 316 BULLETIN No. 189 [June, CABBAGE, Brassica oleracea Atkinson,4 in 1895, in his article on damping-off diseases, men- tioned cabbage seedlings as being susceptible to damping-off by Rhi- zoctonia. Duggar and Stewart32 in 1898 received from Illinois specimens of cabbage seedlings which had been diseased by Rhizoctonia. They found that the disease sometimes affected very young seedlings, caus- ing damping-off, but that it was mpre common after the plants had developed one or two true leaves. In the latter instances, small lesions at or below the surface of the soil characterized the disease. Later, Duggar and Stewart found Rhizoctonia causing a sim- ilar disease of cauliflower seedlings in New York. The plants showed ulcera- tion at the bases of the stems, the entire cortex in some cases having disap- peared. Fawcett40 reported a stem rot of cabbage seed- lings due to Corticium va- gum B. & C., in Florida, in 1909. According to his description, the disease was a typical stem rot, with a softening of the epi- dermis followed by a shriv- FIG. 10. — STEMS OF YOUNG CABBAGE PLANTS INOCU- LATED WITH Rhizoctonia Solani FROM CARNATION FIG. 11. — STEM OF AN OLD CABBAGE PLANT WHICH HAD BEEN PLACED IN A BENCH INFECTED WITH Rhizoc- tonia Solani FROM CARNATION (Ex- periment 9) PARASITIC RHIZOCTONIAS IN AMERICA 317 eliiip of the outside tissues and a browning of the leaves. However, the plants so affected did not wilt down entirely, and many of them recovered. CANDYTUFT, Iberis sp. During June, 1914, a few plants of candytuft that had been grow- ing in three-inch pots in the floricultural greenhouses, rotted off at the surface of the ground. The symptoms were similar to those described for sweet alyssum. Microscopic examination of diseased tissue re- vealed R. Solani in every case. Dense masses of hyphge covering the leaves and stems of these plants were plainly visible. Duggar and Stewart32 in 1901 reported damping-off by Rhizoctonia of cuttings of candytuft in New York. CARNATION, Dianthus caryophyllus Khizoctonia Solani attacks carnation plants of all ages, both in the field and in the greenhouse, causing not only stem rot, but damping- off of cuttings, of which it is one of the principal causes. The symptoms of stem rot of carnation are very characteristic of the effects of R. Solani (Fig. 1). The fungus usually attacks the stem of the plant at the surface of the ground or occasionally just above or below. As a rule, the first indication of the disease is a pale green color of an entire plant or of a single branch. This lighter color can be noticed in most cases for several days before the actual wilting takes place. During cloudy weather the plant does not wilt for two weeks and sometimes for even longer, altho the stem may be almost completely rotted ; in sunny weather wilting occurs much sooner. If the stem of a plant that shows the first sign of wilting is pressed just at the surface of the soil, a soft place is felt and a slight twist is sufficient to slough off the bark. Beneath this is a slimy, wet area, which gives this rot its characteristic name. Sometimes, however, the stem is dry at the point of attack, and upon being broken off, the fibers appear to be separated and stringy. The fungus enters the cracks in the corky layer of the bark and at- tacks the cambium layer, causing the sloughing off of the bark. It then penetrates the woody tissues, and can be found even in the pith. The plant may remain alive after the cambium layer is destroyed until the fungus plugs the vessels. If a diseased plant is left in the soil for some time, the mycelium overruns the stem, and dark, round sclerotia are formed either directly on the bark or in the crevices, or cracks. The Rhizoctonia disease of carnation has been known to florists ever since carnations have been grown as a commercial crop in the greenhouse. In Volume I of the American Florist, 1886, is found the following paragraph, which is probably the first published statement concerning the stem rot of carnation in this country. ' ' In a few days plants began to show signs of wilting, and upon examination I found them rotted off just at the top of the ground, tho half an inch under the ground the stems appeared perfectly healthy." 318 BULLETIN No. lcS9 [June, 1916] PARASITIC RHIZOCTONIAS IN AMERICA 319 While the cause of the disease was not known at that time, from the description of the symptoms it is not to be doubted that it was due to Rhizoctonia. A great loss of plants from stem rot occurred thruout the country about 1900. Below are given a few excerpts from notes on this dis- ease which have appeared during the last thirty years, some of which agree with our present-day ideas: 1886. "Deep planting causes the disease in many houses. " "In our opinion high temperature and deep planting have much to do with the disease. ' ' 1898. ' ' The most dangerous disease that attacks the carnation. Some varie- ties appear more subject to this disease than others, and there is considerable complaint about Flora Hill and Silver Spray this season. The most common error that very often leads to this disease is too deep planting. The plants should never be planted deeper than they stood in the field, preferably not so deep. The stem of the plant should be out of the ground sufficiently to hold the branches away from the soil. I believe this disease is not found on carnations alone, but on other plants too, and the spores of this fungus may have been embedded in the soil, carried over or imprisoned, dormant in the plant from the cutting bench. ' ' To check and prevent the spreading of this disease, dust flour of sulfur over the plants, and shake them so it will lodge on the stem and branches and on the soil around the stem. ' ' 1900. "Climatic conditions rather than anything else are the chief causes of the trouble. High ranges of temperature whether in the cutting bench, field, or house, the results are the same, the amount of rot varying with preceding condi- tions. Thus, after heavy rains inducing soft growth, a rise of temperature into the 90 's is a capital condition for the development of stem rot. Some varieties are also more susceptible to attacks than others, the woodier ones being able to withstand it more than those of soft growth." 1904. ' l Stem rot is due to allowing plants to become pot-bound. "Rich soil with too much manure causing a rapid growth causes stem rot. I believe this to be responsible for more stem rot than all other conditions com- bined. Too deep planting also favorable for stem rot. Water when absolutely necessary and then water thoroly. ' ' 1906. "Presence of wounds on the bark, or punctures made by insects; faulty planting; sour or too highly enriched soil; lack of drainage; careless cul- tivation; lack of fresh circulating air; the maintenance of too great heat com- bined with atmosphere heavily charged with stagnant moisture during the time when the outdoor stocks are housed, will cause stem rot to become severe in the benches. ' ' 1907. "Stem rot is the most dreaded and only disease of carnations in the South. ' ' 1909. "Stem rot more dreaded in South than in North." 1911. "Fresh air, plenty of circulation, a sweet soil, and proper watering will avoid to a great extent the appearance of stem rot or stop its spread. Weather conditions seem to play an important part, and in most cases as soon as cold nights are the rule, our troubles grow less. The greatest benefit is derived thru a clear and rather dry atmosphere. Deep planting not so important. Too much manure not necessarily a cause of stem rot. "Stem rot is more prevalent in sour soils than others. The surface of the soil should be kept open by frequent scratching. A dry interior and a wet surface is very conducive to stem rot." 1913. "Stem rot in the South is more serious than in the North." The following older carnation varieties have beeen reported as being especially susceptible to stem rot : La Purite, Crimson King, De Graws, Sewan. Flora Hill, Silver Spray, McGowan, Portias, Scott, Jubilee, 320 BULLETIN No. 189 [June, Craig, Boston Market, Crane, Lawson, Lady Bountiful, Winsor. Sev- eral of these varieties are still propagated by a few growers and with good success, but the majority of them have been discarded. Of the newer types no one seems to be more susceptible than the others. To Duggar and Stewart30 is owed the discovery that Ehizoctonia is the cause of stem rot of carnation. This they proved conclusively in 1899 by inoculation experiments with pure cultures, repeated many times. Duggar and Stewart state that this stem rot is one of the most troublesome of the carnation diseases and probably occurs thruout the United States wherever the carnation is grown. Stewart123"124 at the same time distinguished between two distinct diseases, both called ' ' stem rot. ' ' One is caused by Rhizoctonia, and the other by Fusarium. Card and Adams13 of Rhode Island studied methods of control of both Fusarium and Rhizoctonia rots. They came to the conclusion that the use of clean, fresh sand in the cutting bench helps to control the fungus. They also found that stable manure does not favor the spread of the disease. In 1902 Stone and Smith129 reported carnation stem rot in Massa- chusetts. Two years later Clinton14 reported the presence of the disease in Connecticut. In 1906 Heald57 stated that it was found in the field and in the greenhouse near Lincoln, Nebraska. Blake and Farley10 in New Jersey conducted a number of soil experiments for the control of stem rot. CARROT, Daucus carota Occasionally R. Solani causes damping-off of carrot seedlings, but the plants seem to be more susceptible later, when the fleshy root is formed. Here the rot starts at the crown and works up into the leaf bases. It also progresses into the interior of the fleshy root, as a rule showing no signs on the exterior for some time. In some cases lesions are found on the exterior of the carrot and on the larger secondary roots where they branch from the fleshy part. Duggar and Stewart32 were the first to find a disease of carrot due to Rhizoctonia. In 1911 Heald and Wolf59 reported from Texas the Corticium stage of the fungus on carrot. They stated that the roots were covered by white, ropy strands of the fungus, but that no serious rotting was observed. CELERY, Apium graveolens A damping-off of celery seedlings in flats by Rhizoctonia Solani has been observed in the Station vegetable-gardening greenhouses. The symptoms are similar to those described for beets. During a search in the market in the winter of 1914 for leaf spot and soft rot on celery, several bunches shipped from New York were PARASITIC KHIZOCTONIAS IN AMERICA 321 found to have a brown mycelium and many small sclerotia between the stalks near the base. The fungus was causing no injury to the celery. When examined in the laboratory, the mycelium and sclerotia proved to be those of Rhizoctonia. Pure cultures of the fungus were obtained readily from the sclerotia. Repeated examinations of new shipments of celery from New York showed that in the majority of cases Rhizoc- tonia was present between the stalks. Duggar and Stewart32 in 1901 were the first to report Rhizoctonia causing a destructive damping-off of celery seedlings. Rolfs95 in 1905 reported a damping-off of seedlings in Florida caused by Corticium vagum B. & C. Van Hook186 found a Rhizoctonia associated with a root rot of celery in the field. He did not believe, however, that this fungus was the cause of all the trouble. Affected plants never attained full size, and an examination of the roots showed considerable decay. The disease seemed to affect the main roots, which rotted off rapidly near the crown. The fact that seed beds in new soil did not entirely control the trouble showed that the fungus Rhizoctonia was present in the new soil, tho not in any great amounts. Halligan,51 in Michigan, has also studied the damping-off of celery plants in the seed bed. Centaurea gymnocarpa In the spring of 1914 a large number of seedlings of Centaurea gymnocarpa, including some of those which were potted, damped off. By June many of the potted plants were dying with stem rot, the dis- ease having been carried over on affected seedlings and in a few cases, no doubt, on healthy ones. Microscopic examination and pure cultures showed that in each case R. Solani was present in the diseased tissues. The progress of the disease was rather typical. The first symptom was the wilting and drying up of the foliage. On pulling up the plant, a number of the leaves were seen to be rotted off at the crown, while the bark on the stem below the surface of the ground sloughed off and the tissues beneath were wet and stringy. CLOVER, RED, Trifolium pratense In the spring of 1914 damping-off of red and Japanese clover was observed in the agronomy greenhouses. A culture easily obtained from the fungus appeared to be the same in all respects as the one isolated from alfalfa seedlings which were growing under similar con- ditions in close proximity. Stevens and Wilson 122 in 1911 reported that in a field of clover in North Carolina the roots were being attacked by Rhizoctonia and were suffering some damage. This is the only instance in which Rhizoctonia has been reported as injuring clover in the field. 322 BULLETIN No. 189 [June, COLEUS, Coleus sp. In November, 1912, cuttings of coleus began to damp off in a bench in the floricultural greenhouses. The variegated green varieties seemed more susceptible to the fungus than the variegated red and yellow. The trouble was found to be due to R. Solani. The infected cuttings showed characteristic lesions on the stems at the surface of the sand. These lesions were quite large and distinct, brown in color, and depressed several millimeters at the center. They were generally found on one side, but in some cases the whole cutting was girdled. Practically all the coleus cuttings in the bench damped off in this manner. During October, 1913, Khizoctonia was found causing a damping- off of coleus seedlings planted very close in flats. About half the plants damped off. Duggar and Stewart32 reported a damping-off of coleus cuttings in New York, caused by Rhizoctonia, similar to that observed at this Station. CONIFEROUS SEEDLINGS The first case reported of damping-off of white-pine seedlings due to Rhizoctonia was by Duggar and Stewart,82 from New York. Ten years later Clinton17 mentioned the damping-off of a number of conif- erous seedlings. Hartley,55 who made a study of the damping-off of coniferous seed- lings in the West, found that Rhizoctonia is one of several organisms involved. He wrote as follows : ' * Khizoctonia (probably Corticium vagum B. & C.), which ojuises dumping-off of very young seedlings, sometimes continues to work in patches till the plants are two months old or even more. On sandy soil, when seedlings from five to nine weeks old are killed, the youngest and deepest parts of the roots are usually first attacked. At Halsey, roots of Eocky Mountain yellow-pine seedlings about seven weeks old have been attacked at points as much as eleven inches below the ground surface. In many plants as old as this the older parts of the roots resist the en- trance of the fungus which has rotted the younger parts and throw out new root branches, so that recovery takes place without any evidence of the damage being shown by the plant above ground. ' ' Coreopsis lanceolata Duggar and Stewart82 in 1901 mentioned the fact that next to a plot of sweet williams that were being killed by Rhizoctonia, were two rows of Coreopsis lanceolata which were also diseased. They stated that ' ' only a few plants were killed, but from many of them the lower leaves had rotted away. The rot seemed to start in the base of the petiole, where it came in contact with the soil. The decaying leaves were overrun with Rhizoctonia." WIG] 1'AKASITIC KHIZOCTONIAS IN 323 CORN, Zea mays In 1914, during the progress of the soil survey for R. Solani the fungus was found frequently on corn roots in the field. It could not be determined whether the fungus penetrated the roots or not but there was no question as to the abundance of the mycelium on the roots. Rolfs95 in 1905 reported Corticium Vagum B. & C. on corn in Florida. COTTON, Gossypium lierbacsum Glover40 in 1855 described a respects is the same as the disease FIG. 13.-STEMS OF YOUNG CARNA- TION PLANTS INOCULATED WITH KmzocTONiA FROM COTTON, SHOWING LESIONS CHARACTERIS- TIC OF SORE SHIN OF COTTON CAUSED BY THE SAME FUNGUS sore shin of cotton, which in some of seedling cotton caused by Rhizoc- tonia. He stated that ' ' the cause is attributed by many to cold, cutting winds, when the plant is very young. Others, however, assert that when a high wind shakes a tender plant, the main stem is so much bent and twisted that the sap ves- sels are upturned and a serious in- jury occurs." One of the causes of sore-shin disease of cotton remained undis- covered until Atkinson,5 in 1896, found in the diseased tissues a ster- ile mycelium, which he later identi- fied as Rhizoctonia. By means of pure-culture methods and inocula- tion experiments he further proved that this sterile fun^us was the cause of sore shin and also of seed- nng rot and damping-off of cotton. TT j -u AT. T-»T.- • •»• He Ascribes the Rhizoctonia dis- ease of cotton as follows : ' ' There are several phases of the disease. Sometimes the tissues undergo a soft rot which progresses very rapidly, and the early stages are not marked by any striking color characteristics. Another phase may progress rapidly or slowly and is usually quite well characterized by a reddish brown color which accompanies it. This phase is also characteristic in that it is usually manifested on one side of " the stem in the form of an ulcer which gradually deepens until the vascular sys- tem is reached, when the life of the plant becomes really endangered. Even when this stage is reached, however, the plant may, and does frequently, recover. "This latter phase is characteristic of a very common disease of seedling cotton. It is called by the planters in many places 'sore shin.' * ' The diseased portion of the plant is just beneath the surface of the ground and presents an area of shrunken tissue of a dull brown or reddish color. The 324 BULLETIN No. 189 [June, size of the shrunken area and the depth of the injury are proportionate to the serious condition of the ulcer, as it may be termed. If the injury remains con- fined to the superficial tissues, the plant will usually recover. It does sometimes recover when the injury reaches the vascular tissue, but more frequently death results when the trouble has progressed thus far." No further original work has been done on this disease since the time of Atkinson, altho several of the southern experiment stations have published bulletins on cotton diseases, including the sore shin and seedling rot due to Rhizoctonia. - Dianfhus R. Solani was isolated from diseased plants of Dianthus barbatus (Newport Pink), during July, 1913, in the perennial garden of the Station. This variety and Diawfhus barbatus (single mixed) were much more susceptible to stem rot than were any of the other varieties grown. In fact, practically every plant of these two varieties died from stem rot during the summer. These varieties are more like the carnation than any of the others, and when affected, the symptoms of the disease were very similar to those of stem rot of carnation. The first evidence of the disease was the pale green color of the leaves, followed in many cases by a sudden wilting of the foliage. When plants in this stage were pulled up, the bark readily sloughed off, leaving the wood exposed. When plants in the later stages of the disease were pulled up, the stem usually broke off at the surface of the ground, exposing stringy tissue. During the same month, a disease of Dianthus sequeri and D. plumarius was under observation. Diseased parts of these plants yielded Rhizoctonia in every instance. In the case of D. sequeri the fungus seemed to be living saprophytically among the numerous pros- trate, bushy branches. The brown strands of the mycelium could be plainly seen running thru the bushy mass of the plant. Only a few plants died. Unlike the case of D. barbatus, there was no characteris- tic sloughing off of the bark, but a more or less general rotting of the whole stem, which left the tissues very dry and stringy. The attack was not confined to the main stem, but affected any of the branches which touched the ground. Most of the plants of D. plumarius, occupying a space about three feet long, died from attacks of the fungus. The symptoms of the dis- ,ease were very similar to those of D. sequeri, the rotting appearing to extend gradually from one point thru the whole stem. As with D. sequeri also, the bushy habit of the plant gave ample protection to the fungus, and the radiating strands of the brown mycelium of Ehizoc- tonia were visible to the naked eye. ^ Duggar and Stewart32 in 1900 found a badly diseased plot of Dianthus barbatus in which 90 percent of the plants, in the course of the season, died from stem rot due to Rhizoctonia. 1916} PARASITIC EHIZOCTONIAS IN AMERICA 325 EGGPLANT, Solanum melongena During August, 1912, while some field observations were being made on carnation stem rot, the fruits of a number of eggplants in an adjoining field were found to be rotting at the point where they touched the ground. The decay spread in all directions from this point, making a sunken, brown area ; this was followed by the soften- ing and subsequent collapse of the surrounding tissues. Fruits showing this decay were brought into the laboratory and placed under a bell jar. Around the diseased spot there soon developed a thick mass of mycelium, which on microscopic observation was found to consist of hyphae of Fusarium and Rhizoctonia. The decaying spots contained no fungous threads, but were completely filled with bacteria. On plat- ing, pure cultures of R. Solani were obtained. The cause of the pri- mary infection is not known. It is very probable that both the Fusar- ium and Rhizoctonia entered the tissues where the epidermis had been destroyed. In July, 1913, the damping-off of a number of eggplant seedlings in the vegetable greenhouses was noticed. This was shown, by pure cultures of the diseased material, to be due entirely to Rhizoctonia. The fungus produced the characteristic lesions on one side of the seed- lings at the surface of the soil, causing the stem to break. Atkinson,4 in his account of damping-off diseases, mentioned eggplant seedlings among those susceptible to attacks of the sterile fungus (Rhizoctonia). Rolfs95 reported the presence of the Corticium stage of Rhizoctonia on mature plants in an irrigated garden. Here the plants affected drooped for a time and then wilted and died. Le- sions were formed on the stems at the surface of the ground. Wolf140-141 in 1914 reported damping-off and a fruit rot of eggplants due to Rhizoctonia (Corticium vagum B. & C.), but he does not re- gard the fungus as the cause of serious injury to eggplants. FIVE-FINGER, Potentilla sp. A number of five-finger plants were found to be infected with R. Solani during June, 1914, in inoculated sections in the floricul- tural greenhouses. The mycelium of the fungus was present at the nodes which touched the soil and also at the bases of the plants, where crown rot was developing. FOXTAIL GRASS, Set aria glauca Several plants of foxtail grass growing under the same conditions as the preceding host, five-finger, showed a root infection. Gypsopliila repens A number of GypsopMla repens plants were found diseased in the herbaceous grounds during July, 1913. Pure cultures of the diseased 326 BULLETIN No. 189 [June, material showed the causal organism to be R. Solani. The plants were bushy, so that some of the branches and leaves were in contact with the soil. The symptoms and appearance of the disease were similar to those described for Dianthus. LAMB'S QUARTERS, Chenopodium album During the summer of 1913 several wilted Chenopodium plants were observed along the border of the old herbaceous grounds of the Station. On pulling up the wilted ptants, it was found that R. Solani was the cause of the wilting. The fungus did not enter very deep into the tissues, but rather girdled the stem and formed a scurfy layer. Duggar and Stewart32 in 1901 reported the occurrence of Rhizoc- tonia on Clienopodium album. Lavatera arborea variegata During March, 1913, in the floricultural greenhouses, a number of seedlings in small seed pans, among which were several pans of Lava- tera, began to damp off in a manner characteristic of R. Solani. Pure cultures of diseased seedlings yielded this fungus. Strands of the brown mycelium could be seen on the surface of the soil and extending up on the stems and leaves. This was noticed again in the spring of 1914. LETTUCE, Lactuca sativa Atkinson4 in 1895 mentioned the damping-off of seedling lettuce, among a number of other plants, by a sterile mycelium which later proved to be Rhizoctonia. Stone and Smith128 found that R. Solani caused a rot of green- house lettuce, altho the disease was not common. The first appearance was on the lower leaves where they lay on the ground ; a brown rot set in, which spread thru the leaf in a very characteristic manner. The green blade rapidly rotted away, leaving the midrib and stalk as sound as tho the blade had been carefully cut away or had been eaten by insects. Duggar and Stewart32 observed the damping-off of lettuce seed- lings by Rhizoctonia for a number of years. They found that at or near the surface of the ground the tissues become water-soaked in appearance and unable longer to support the seedling, so that it falls to the ground, the fungus invading all parts. Within a day or two this fungus, under favorable conditions, wilted down and destroyed whole boxes of lettuce seedlings. Duggar and Stewart also observed several times what was apparently the same fungus causing a disease of mature lettuce plants. On the older leaves the leaf blades alone were affected, but the more delicate inner leaves succumbed entirely, blackening and decaying with the progress of the disease. 1916} PARASITIC KHIZOCTONTAS IN AMERICA 327 In 1903 Sol by104 reported the presence of a rosette disease of let- tuce, which he described as follows: "The plants affected showed, usually not long after transplanting, but occasionally at other stages, a failure to send out central leaves freely. The leaf -bearing axis re- mained shortened, and the last leaves formed remained short, making a very striking contrast to the remainder of the plants in the bed and to the lower leaves of the same plant. (Frequently the plants overcome this tendency and make a fair amount of product with longer time.) Examination of the roots showed areas occupied by the hyphae of Ehizoctonia. ' ' In 1906 Selby106 treated at length the control of rosette in lettuce due to Rhizoctonia. - 14 DAMPIXO-OFF OF LAVATERA SEEDI.INCS P.Y I!Iti:octoHui (Experiment 9) 328 BULLETIN No. 189 [June, Iii 1905 Rolfs95 reported the presence of the perfect stage, Cor- ticium vagum B. & C., on lettuce from Florida. Lobelia erinus (Single Blue) The lobelia plants in the floricultural greenhouses in 1914 were small and sessile, and covered the tops of the pots in which they were growing. In June a number of them began to die. On close exami- nation, strands of R. Solani could be seen spreading thru the mass of plant material. The low-lying leaves afforded a good hiding place for sow bugs, and no doubt they helped in carrying the fungus from one pot to another. Attacks of Rhizoctonia on other varieties of lobelia have been observed in the greenhouses a number of times. ONION, Allium sp. A culture of Rhizoctonia isolated from onion seedlings was ob- tained from Cornell University by Mr. H. W. Anderson in 1911. Since that time the author has worked with this strain both in the laboratory and in the greenhouse. From its morphological and physiological behavior, it must be classed as distinct from the other strains. Dr. I. C. Jagger states in a letter that he first isolated this form from onion on May 29, 1911, from seedlings growing on muck soil in New York. He found that the Rhizoctonia mycelium was always con- fined to the first, or seed, leaf and that damping-off ceased as soon as the second leaves had developed. PANSY, Viola tricolor During the fall of 1913 pansy plants were placed in a solid bed, in the floricultural greenhouse, as a border for sweet peas. At that time some of the sweet-pea plants died, and eventually a culture of R. Solani was obtained from them. The following April several pansy plants in the vicinity of the spot where the sweet peas had died became diseased and later died. A culture showed the trouble to be due to Rhizoctonia. Later a large number of the plants in the row died. The fungus attacked the plant at the crown and caused a rapid rot. The prostrate branches, the petioles of the leaves, and even the leaves them- selves were also rotted in a characteristic fashion. The strands of the mycelium could easily be seen ramifying between the rotting mass arid the soil. PLANTAIN, Plantago aristata Diseased plants of plantain were found during June, 1914, in inoculated sections in one of the floricultural greenhouses. The mycelium of R. Solani was present around the bulbous base of the 1016] PARASITIC RHIZOCTONIAS IN AMERICA 329 plants, causing a crown rot. In one or two cases several leaves were completely rotted at the crown. POINSETTIA, Euphorbia pulcherrima About October 7, 1912, young poinsettia plants were taken from the cold house (50° to 60 °C.) of the flori cultural greenhouses and put in a box with a glass top. They were then placed near the cutting bench, in which a number of plants of various kinds were damping off. The poinsettia cuttings shortly afterwards began to die off rapidly. The characteristic lesions on the stems of the young plants and pure cultures of the diseased material indicated that this condition was due to R. Solani. The lesions, instead of being on one side and more or less localized, in almost every case formed a collar around the stem at the surface of the soil. The collar was about 2 to 3 millimeters wide, somewhat depressed, and of a dark color. Strands of the brown mycelium were visible spreading over the soil in the pots. This infec- tion probably had its origin in the cutting bench. POTATO, Solanum tuberosum On the potato R. Solani exhibits a number of interesting charac- teristics, which vary with climatic conditions, age of the host, and part of the plant attacked. The sclerotial stage of this fungus has been observed on practically every Illinois potato tuber examined by the writer. Moreover, in every shipment from other states which has been examined, the fun- gus has been found present. The tubers affected were dotted with brownish black sclerotia of various shapes and sizes (Fig. 15), but so far as could be determined, they were causing no direct injury. This type of Rhizoctonia disease of potato is the one most commonly found in the United States. R. Solani also causes, under certain conditions, a russeting, or scab, a cracking of the tuber, the formation of pits at or near the len- ticels, and a wet rot of the tuber. These types of injury have been ob- served by Rolfs92'93 in Colorado, by Orton73 in various states, and by Morse and Shapovalov69 in Maine. On the plant itself this fungus produces various types of diseases. In many cases young plants are completely cut off before they reach the surface of the ground. Older plants that are severely attacked just below the surface of the ground usually die off quickly. If they are only slightly attacked, the fungus produces small lesions on the stems, the plants take on a dwarfed and unhealthy appearance, and the tubers remain small, altho the plants usually live thru the sum- mer. When the stem is girdled by the fungus so as to prevent trans- location entirely, large tops are produced, aerial tubers are formed, 330 BULLETIN JS'o. 189 [June, FIG. 15. — POTATO TUBER SHOWING THE SCLEROTIA OF Ehizoctonia Solani J01t>] PARASITIC Kumx TON IAS IN A.MKKICA 331 and income cases a curling of the leaves or resetting results. When the main stem is attacked below the surface of the soil and the stolons are cut off, the condition known as "little potatoes" is produced; in such cases a cluster of small, short-stemmed tubers is formed above the wound. The production of aerial potatoes, rosette, and leaf curl- ing also occurs when the stolons are attacked and the young tubers are cut off. These abnormal developments of the potato are usually associated, and are secondary physiological effects due to disturbances of the nutrition of the plant. They occur most frequently on poorly drained land and especially on heavy soils. Rolfs92 attributed the potato failure of 1902-03 in Colorado to little potato. Selby103 in Ohio, in his studies of the Rhizoctonia dis- ease on potato, gave particular attention to rosette. In 1914 Morse and Shapovalov09 concluded that the Rhizoctonia disease of potato is of a more serious nature than is generally considered. In one field which they had under observation for several seasons, they attributed the poor and uneven stands, unexpected low yields, early ripening, and death of the tops to Rhizoctonia. In most cases they confirmed the observations made by Rolfs. Recently investigators all over the country have been emphasizing the serious nature of the disease. In January, 1915, material of Rhizoctonia Crocorum on potato tubers was received from Mr. F. D. Bailey of the Oregon Agricultural Experiment Station. On comparing it with Rhizoctonia Solani, it was found to be entirely different in all respects. However, this fungus is identical with the fungus on alfalfa reported by a number of observers (Webber, Heald, and Freeman) as R. Crocorum. Thus it appears that R. Crocorum is present in this country on alfalfa and on potato tubers. Bailey8 describes the Rhizoctonia disease of potato as follows : "The surface was almost entirely covered with a dense, felt-like mat of a chocolate color when dry, violet -brown when moist. This mat was found to be composed of mycelium which had long narrow cells and a branching habit char- acteristic of Rhizoctonia. The greater part of this mycelial mat could be easily removed, and beneath this the surface of the tuber was covered with very small dark spots. These spots appeared to the unaided eye as minute eruptions of the skin. Under the microscope one can see the mycelial threads attached at these points, and a freehand section thru such a spot shows it to be a structure com- posed entirely of interwoven fungus threads forming a sclerotium. No evidence of differentiation or any type of spore formation within this body could be found on examination of many sections. The portion of the sclerotium near the sur- face is composed of cells that are very deeply colored, giving the black appear- ance. The outer surface of the sclerotium is seen to project above the surface, while the lower or underlying portion is embedded in the outer cortical layers of cells of the tuber. Furthermore, there is a strand of fungus tissue extending deeper than the sclerotium, which connects it with a layer of the same type of fungus tissue spreading between the cortex and parenchyma from the poini where this strand reaches the parenchyma. "Attempts to grow this fungus in culture failed. This has boon the experience reported in attempts to grow Ehizoctonia violacea Tul." 332 BULLETIN No. 189 RADISH, Raphanus sativus \June, Damping-off of radish seedlings by R. Solani has appeared sev- eral times in the floricultural greenhouses. During May, 1914, an at- tack of Rhizoctonia on mature radishes was observed in the writer's home garden. The first sign of the disease was the yellowing of the foliage, followed by the wilting of the leaves. On pulling up a plant, the crown was found to be rotted at the base of the leaves. The rot progressed slowly and killed only a few of the plants. After it had proceeded for some length, the radishes cracked farther down. This is very characteristic of the disease at this stage (Fig. 16). In 1895 the damping-off of radish seedlings by a sterile fungus, which was later identified as Rhizoctonia, was first reported by Atkin- son.4 Duggar and Stewart32 in 1901 noted a disease caused by Rhi- zoctonia of mature radishes forced in a greenhouse. The disease caused a soft rot of the crown or lesions in this region. The leaves were generally unaffected until a large part of the root had decayed. Plants in all stages of growth were affected and killed. Duggar and Stewart also found a Rhizoctonia in connection with the damping-off of radish seedlings in the greenhouse. FIG. 16. — LATE STAGE OF KOOT ROT OF RADISHES CAUSED BY Rhizoctonia Solani PARASITIC RHIZOCTONIAS IN AMERICA 333 In 1904 Clinton1 4 observed a damping-off and root rot of radish due to Rhizoctonia. Apparently the disease was not very serious. Stewart125 in 1910 also reported a damping-off and root rot of radish due to Rhizoctonia. Infection took place first at the level of the soil, causing the leaves to have a wilted, drooping appearance. From this point the disease spread into the leaves and roots of the plant, soon causing death. On mature radishes, decayed spots of irregular shape were produced, and at an advanced stage the diseased portions of the plant were covered with a white, felted mycelium. RHUBARB, Rheum rtiaponticum In 1901 Duggar and Stewart32 reported a disease of rhubarb, on Long Island, which they had had under observation for several years. They described the disease as follows : "An unthrifty condition of the plants was noticed, followed by the rapid dying off of many of the leaves. The affected leaves became dry and shrunken in appearance and soon fell to the ground. Where a field was badly affected, the majority of hills showed the trouble to the extent of at least a leaf or two. In several instances from one-fourth to three-fourths of the leaves were already dead. An affected leaf breaks off readily just beneath the surface of the ground, and old dead leaves rotted off in this region. The general appearance reminded one strongly of the effect of Ehizoctonia upon beets. There was very little super- ficial mycelium visible to the unaided eye. Microscopic examination showed hyphse of a Khizoctonia both superficially and immediately under the surface where the leaves were rotting?7 Clinton14 has also reported a stem rot of rhubarb due to Rhizoc- tonia. He found the fungus at the base of leaf petioles, causing dark, sunken cankers. SALVIA, Salvia splendens The symptoms of the Rhizoctonia disease of salvia observed in the flori cultural greenhouses were similar to those described for coleus. All varieties of the cuttings in the bench seemed to be equally suscep- tible. It has been shown that the serious damping-off of the salvia, al- ternanthera, and coleus was due to the fungus which was first brought in on the mature alternanthera plants from which cuttings were made. (See Alternanthera, page 310.) • Santolina cliamcecyparissus In 1914 a number of plants of Santolina cliamcecyparissm growing in pots next to the Centaurea gymnocarpa in the floricultural green- houses, were found to have a typical stem rot, due to R. Solani, very similar to the disease as described for that plant (see page 321). The fungus could be distinctly seen running thru the bushy branches. 334 BULLETIN No. 189 [June, Sedum sp. A few plants of Sedum anglicum, together with several other spe- cies of Sedum, were found diseased, in July, 1913, in the herbaceous grounds. The progress of the disease was very slow ; few plants were killed during the entire summer. For the most part, the fungus seemed to live saprophytically at the base of the plant. It was also found on healthy plants of this genus. About six species were planted in a row in the garden, and all were affected in much the same way. SORREL, Rumex acetosella In June, 1914, a number of sorrel plants were found diseased in an inoculated section in the greenhouse. The stems of the plants were covered with the brown strands of mycelium, and a few of the leaves were rotted off at the crown. Pure cultures of the diseased parts yielded R. Solani in every case. SWEET PEA, Lathy r us odor at us During July, 1912, when the young sweet peas in the field were about one-third to one-half grown, occasional vines showed evidence of disease by turning yellowish, wilting, and finally drying up en- tirely. An examination of the affected plants showed that they were more or less separated from their roots near the surface of the ground. Pure cultures of the diseased material yielded R. Solani in all cases. In November, 1913, several diseased seedling's were brought in from the plant-breeding greenhouses. On close examination the stems showed the characteristic lesions caused by Rhizoctonia. The same trouble occurred in the floricultural greenhouses the past two seasons, but in no case was it severe. During the winter of 1913, the writer was called to Chicago to look over a range of greenhouses devoted to the growing of sweet peas. Sweet-pea plants of all ages were seriously affected. Dead plants were scattered thru the whole house. Close examination of the diseased plants revealed the fact that Rhizoctonia was causing the trouble. Apparently it started in the seed pans and continued to work until the plants were ready to be discarded. The symptoms in each case were the same — yellowing of the foliage, followed by the wilting and dry- ing up of the plants. Characteristic lesions, which finally cut the stems off at the surface of the soil, could always be found on the dis- eased plants. The root systems were much dwarfed. In 1908 Clinton16 observed in Connecticut a damping-off of sweet peas due to Rhizoctonia. Taubenhaus130'131 in describing a Rhizoc- tonia rot of sweet pea at different stages, states that he found it quite destructive to the plants when they are in the seedling stage. J-91G] PARASITIC RlllZOCTOXlAS IX AMERICA 335 TOBACCO, Nicotiana sp. In 1904 Clinton14 noticed a seed-bed rot of tobacco, which he thought was due to Rhizoctonia. The same year Selby105 observed a similar bed rot of tobacco in Ohio caused by Rhizoctonia. He stated that the specific characteristics of the fungus do not differ essentially from those of its forms on other plants, including potato. Clinton,15 in making another report on this disease, in 1906, stated that the injury to the plants was slight and was confined, as with the potato, to the underground parts. Johnson63 has carried on some extensive work on Rhizoctonia, with a view to controlling the damping-off of tobacco seedlings. TOMATO, Lycopersicum esculentum A damping-off disease of tomatoes caused by Rhizoctonia has been noted from a number of states ; the symptoms of the disease are the same as have been described for a number of other plants, such as eggplant. In connection with his work on the potato rosette resulting from Rhizoctonia, Selby104 also mentioned a tomato rosette caused by the same fungus. He stated that the tips of diseased plants showed rather long internodes and dwarfed leaves, with somewhat curled-leaf aspects, while the roots had lesions and other similar features found in potato rosette. Rolfs95 in 1905 stated that he frequently found the Corticium stage on the tomato plant, but that apparently the plants do not suffer ma- terially from its presence when planted on well-aerated land. He described it as follows : "The fruiting stage of the fungus develops freely on the stem just above the surface of the ground, often extending up the stem for a distance of six inches. As a rule the fungus does not penetrate the tissue here, but simply covers the stem of the plant. The tomatoes which touch the ground are frequently more or less covered by a fruiting membrane of the fungus, which mars the appearance of the ripe fruit. So long as the tomatoes are green and the skin uninjured, the fruit remains sound; however, if the skin is ruptured, the fungus soon destroys it, pro- ducing a brown rot. This organism also frequently gains entrance to the fruit at the stem end. ' ' Orton72 described the rosette of tomato caused by Corticium vagum B. & C. as a disease of minor importance in tomato culture. He stated that ' ' the fungus attacks the roots and base of the stem, forming dark cankers. The effect on the plant is to dwarf and curl the leaves and to restrict productiveness." A fruit rot of the tomato has also been observed by Pool86 and again by Wolf.141 Pool described the symptoms of the fruit rot as follows : "The specimen examined showed no rupture in the external skin visible to the naked eye. The diseased area was plainly distinguishable by the chocolate- 336 BULLETIN No. 189 [June, colored, slightly wrinkled epidermis. An examination of the underlying tissues revealed the same general color and numerous, somewhat darkened filaments pene- trating the cells in all directions." Wollenweber1 42 in 1913 described a species, RJiizoctonia poto- macensis Wr., which causes a fruit rot of green tomatoes. He stated that this species differs from Rhizoctonia Solani in the character of its attacks, in that concentric, subepidermal mycelial zones are formed within the tomatoes. VIOLET, Vioki odorata During the fall of 1913 a number of violet plants in the floricul- tural greenhouses were found to be diseased. A few had stem rot, while on others only the bases of the petioles were somewhat rotted. "Where the pots were set close together and the plants overlapped, the brown strands of R. Solani could be plainly seen spreading out from one plant to another. However, in no case was the disease severe ; it is probable that the fungus was living saprophytically on the lower leaves. Duggar and Stewart32 observed, in a greenhouse in New York, one case of destructive violet stem rot due to Rhizoctonia and a second case similar to the attack described above. ADDITIONAL OBSERVATIONS Beside the hosts that have been mentioned, observations have been made in the floricultural greenhouses of diseased seedlings and cut- tings of a number of other plants, tho no work has been done further than to make a microscopic examination of the diseased material. Below is a list of seedlings and cuttings found damping off in the spring and fall of 1914, with the percentage of loss resulting. In all cases Rhizoctonia proved to be the cause of the trouble. Percentage Seedlings Damping off, April 6, 1914 of loss Amaranthus caudatus 75 salicifolius 90 Bartonia aurea 90 Calendula Pongei 1-2 Celosia Huttoni, var. Thompsonii magnified 75 Chrysanthemum hortorum 30-40 Dianthus chinensis 80 Heddewigii 30 ' ' latifolius 80 Godetia sp 80 Gypsophila muralis 30 Kochia trichophylla 99 Lavatera arborea variegata 5 Linaria Maroccana 5 Linum grandiflorum rubrum. 30 Lychnis coeli rosa 90 Portulaca oleracea 80 Schizanthus sp 2-4 1916] PARASITIC RHIZOCTONIAS IN AMERICA 337 Percentage Seedlings Damping off, September 2, 1914 of loss Aquilegia (6 species) 35 Campanula (8 species) gO Cineraria (several species) 20 Dianthus plumarius 35 Erysimum pulchellum 2 Linaria Cymbalaria 2 Ly thrum sp Matthiola incana (stocks) 2 Primula malacoides 2 ' ' obconica grandi flora Schizanthus (mixed) 2 Silene Schafta • . . 100 Stachys lanata 2 Viola tricolor (3 varieties) 20 Cuttings Damping off, September 25, 1914 Abutilon hybridum, var. Savitzii 100 Acalypha Wilkesiana, var. Toicolor 100 tricolor 100 marginata 90 Ageratum mexicanum vars ; 2 Alyssum odoratum (3 varieties) 100 Coleus (10 varieties) 2 Cuphea platy centra 2 Iresine (Achyranthes) (5 varieties) 95 Petunia (several varieties) 100 Piqueria trinervia (Sterna} 100 Santolina chamcecyparissus 2 Sedum spectdbile 2 Telanthera (Alternanthera} (9 varieties) 2 Vinca major (several varieties) 2 TYPES OF SYMPTOMS From a study of the symptoms caused by Khizoctonia Solani on the various hosts, it is seen that, except for a few minor points, they are the same when appearing on the same type of host. The damping- off of seedlings and cuttings of various plants is identical, as is the rotting of a number of root crops. In most herbaceous plants a stem rot is produced, the symptoms of which are also identical on the vari- ous hosts. On very resistant plants lesions only are formed ; these are apparently identical on the different hosts. INOCULATION EXPERIMENTS The main purpose of these inoculation experiments was to ascer- tain the degree of biologic specialization which may exist between the various cultural strains of Ehizoctonia, or between strains isolated from different hosts or of different geographical origin. With three thousand square feet of glass available in the floricultural greenhouses and with the assistance of the members of the floricultural division, it was possible to carry on cross-inoculation experiments involving about 338 BULLETIN No. 189 [June, 3,000 cuttings, 2,000 plants, and 7,000 seedlings of various kinds. With these, comparisons were made of about forty-five strains of Rhizoctonia. A large number of the strains used in these experiments were iso- lated by the writer from the various hosts found infected with Rhizoc- tonia in this vicinity. Other strains were obtained from various in- vestigators thruout the country. Below is presented a list of the strains used and the source of each. Alfalfa. — A Khizoctonia culture froni alfalfa was received from Dr. C. W. Edgerton, Baton Rouge, Louisiana, November 12, 1912. It was originally ob- tained by Dr. Edgerton in May, 1910, from alfalfa seedlings. Alternanthera E.A.C. — A culture of Rhizoctonia was isolated from infected alternanthera cuttings found in the floricultural greenhouses in the fall of 1912. Alternanthera E.A.F. — This strain was obtained at the same time as the preceding, from mature alternanthera plants in the field. Amaranthus. — In August, 1913, Mr. W. H. Burkholder, of Cornell University, contributed several specimens of Amaranthus retro flexus infected with Rhizoc- tonia, from Irving, New York. The stems were covered with the immature, gray, felt-like mycelium of the Corticium stage. Scrapings of the hymenial layer of this stage yielded pure cultures of Rhizoctonia in every case. Aster. — Early in 1913, Dr. F. A. Wolf sent to the writer a culture of Rhizoc- tonia which was the cause of the damping-off of China aster seedlings in flats in the greenhouse at Auburn, Alabama. Bean. — A transfer of a culture of Rhizoctonia from bean was obtained in December, 1912, from Dr. J. T. Barrett, of this university. He in turn had re- ceived it from Dr. M. F. Barrus, of Cornell University, about 1910. Beet. — A culture of Rhizoctonia was obtained from young seedlings of the garden beet found damping oft' in the vegetable-gardening greenhouses, July 10. 1913. Begonia. — The strain from begonia was isolated by Mr. Anderson from cut- tings found damping off in the floricultural greenhouses in the fall of 1911. Carnation. — During the reason of 1911-12, Mr. Anderson isolated Rhizoctonia from a number of carnation plants received from different sources, and during 1912-13 and 1913-14 the work was continued by the author, so that a comparison of a large number of cultures from diseased plants obtained from various localities was possible. The strains used are given below. ' ' Carnation R.K. ' ' : Isolated by Mr. Anderson from diseased carnation plants obtained at Urbana, Illinois, in October, 1911. "Carnation R.O.": Culture isolated by Mr. Anderson in the fall of 1911, at Urbana. " Carnation R.H. " : Culture isolated from a diseased plant in the floricul- tural greenhouses in the fall of 1911 by Mr. Anderson. ' ' Carnation R.S. ' ' : Isolated from diseased plants received from Kankakee, Illinois, by Mr. Anderson, October 25, 1911. ' * Carnation R. 2 " : Culture reisolated by Mr. Anderson from infected cut- tings in sterilized soil in the spring of 1912. "Carnation R.F.": Isolated from diseased carnation plants gathered in the field in the horticultural grounds, July 24, 1912. ' ' Carnation R.M.2 ' ' : Isolated from a White Enchantress plant in one of the floricultural greenhouses during September, 1912. "Carnation R. 107": Obtained from a plant in the floricultural greenhouses, (September 7, 1912. ' ' Carnation R.F.2 ' ' : Culture obtained from a diseased plant in the field during the summer of 1913. "Carnation R. 121-5": A reisolation of Rhizoctonia was obtained on De- cember 3, 1912, from a diseased plant in one of the inoculated sections of the greenhouse. Carrot. — The strain of Rhizoctonia from carrot used in this work was ob- tained by Mr. Anderson from Cornell University in 1911. Nothing is known of the origin of the culture. 1916] PARASITIC RHIZOCTONIAS IN AMERICA 339 Cauliflower. — A culture of Rhizoctonia from cauliflower was obtained in 1912, from Dr. C. W. Edgerton, Baton Rouge, Louisiana. This culture was isolated from diseased cauliflower seedlings in the summer of 1912, so that it was a comparatively fresh culture when received here. Chenopodium. — A culture was isolated during the summer of 1913 from ma- ture plants of Chenopodium album growing along the border of the old herbaceous grounds back of the floricultural greenhouses. Clover. — A culture of Ehizoctonia from red-clover roots was received from Mr. E. A. Arzberger, Wooster, Ohio, March 3, 1913. The fungus was isolated by him from red -clover roots in the greenhouse in December, 1912. Coleus I. — This strain was obtained from coleus cuttings found damping off in the floricultural greenhouses, November, 1912. Coleus II. — A culture was isolated from coleus seedlings damping off in seed pans, October, 1913, in the floricultural greenhouses. Corn. — The strain from corn was obtained from Dr. J. J. Taubenhaus, New- ark, Delaware, in 1912. He stated that the fungus had been isolated from corn seedlings that were damping off in the greenhouse. Cotton. — Three cultures of Rhizoctonia from cotton received from two sources at different times, were used in these experiments. The strain ' ' Cotton I ' ' was received from Dr. C. W. Edgerton, Baton Rouge, Louisiana, November 12, 1912. This strain was cultured by him in September, 1911, from young diseased plants. The strain ' ' Cotton II ' ' was also received from Dr. Edgerton. This strain was cultured in February, 1912, from the same kind of material as the above. . The third strain, * < Cotton III, ' ' was received from Dr. F. C. Wolf, Auburn, Alabama, December 12, 1912. The fungus was isolated from seedling cotton plants growing in the station greenhouse at Auburn. Diantlius. — Cultures of Rhizoctonia were isolated during July, 1913, from diseased plants of several species of Dianthus growing in the perennial garden. The strains cultured and used in the experiments were * ' D. barbatus N. P.," " D. barbatus S. M., " "D. plumarius," and "D. sequeri. " Eggplant. — Two strains of Rhizoctonia were isolated from eggplant: one, causing a fruit rot, was cultured August, 1912; the other was isolated from seed- lings damping off in flats in the vegetable-gardening greenhouse, July, 1913. Gypsopliila repens. — A culture of Rhizoctonia was isolated during July, 1913, from diseased Gypsophila plants in the perennial garden. Lavatera. — A culture was isolated in 1913 from seedlings of lavatera found damping off in pans in the floricultural greenhouses. Lettuce.— The strain from lettuce was obtained by Mr. Anderson in 1911, from Cornell University. Poinsettia. — Cultures were obtained from damping-off poinsettia cuttings found in the floricnitural greenhouses, October, 1912. Potato. — Several strains from potato were used in these experiments. Two of these strains were obtained from scrapings of the hymenial layer of the Corti- cium stage. "Potato R.P.C. " — A culture of this strain was isolated from fresh potato stems received from Dr. I. C. Jagger, Williamson, New York, September 2, 1912. This material contained the perfect stage, Corticium vagum B. & C. Pure cul- tures of Rhizoctonia were obtained from scrapings of the hymenial layer. "Potato R.P.I." — In response to a letter from Mr. Anderson, Dr. Geo. ] Pethybridge, Clifden county, Galway, Ireland, sent a small box of potato stems containing the perfect stage, Corticium vagum B. & C. This material was sent by post, July 18, 1912, and received August 5. A pure culture of Rhizoctonia was obtained from scrapings of the gray mycelium of the Corticium stage. "Potato R.P.O. " — A culture from potato was obtained by Mr. Anderson from Cornell University. The strain was old and grew very poorly on agar. "Potato R. Sol." — This strain, like the preceding one, was obtained by Mr. Anderson from Cornell University. It also grew very poorly on agar. Eadish.—A culture of Rhizoctonia from radish was obtained from Gorne University, by Mr. Anderson, in 1911. This form was very old and probably h been in culture several years. It was lost in April, 1913. 340 BULLETIN No. 189 [June, Salvia. — The strain from salvia was isolated from cuttings which were found in the same bench with a number of other cuttings damping off, October, 1912. Sedum. — A culture of Ehizoctonia from sedum was isolated from diseased plants found in the herbaceous grounds in July, 1913. Sugar Cane. — A culture of Ehizoctonia isolated from sugar cane was re- ceived from Dr. C. W. Edgerton, November 12, 1912. This culture was obtained in April, 1912. It was fresh and virulent. Thistle. — A culture of Ehizoctonia from thistle was obtained by Mr. Ander- son from Cornell University in 1911. The method of infecting the cuttings, seedlings, and young plants grown in flats and benches, was as follows : Small flats, varying in size with the experiment, were first soaked in a strong solution of formalin for several minutes and then allowed to dry. Steam-sterilized sand or soil and a soil culture of Rhi- zoctonia were then mixed to- gether in the flats and watered. After being tamped down, the flats were left standing for two days in order to allow the fun- gus to spread thru the soil. Later, the cuttings, seeds, or plants were put in the flats and placed in a chamber in the green- house where the moisture could be controlled. Bottom heat was furnished. The temperature var- ied somewhat during the experi- ment, but the average was about 60° F. When only individual plants in pots or in benches were to be infected, a portion of a cul- ture of Rhizoctonia two weeks old on green-bean plugs was placed in contact with the stem of each plant about one-half inch below the surface of the soil, where it would be protected from light and desiccation. In obtaining soil cultures of Rhizoctonia in large quantities. Mason jars with modified covers were found to be very suitable containers. A hole about one inch in diameter was cut in the FIG. 17. — SOIL CULTURE OF RHIZOCTONIA 1916] PARASITIC BHIZOCTONIAS IN AMERICA 341 center of the cover, and a small tin tube about two inches long was in- serted and soldered in. This hole was plugged with cotton. (See Fig. 17.) A mixture of 200 grams of dry sand and 10 grams of corn meal was then placed in the jars and moistened with distilled water until the sand was wet thru. The jars and their contents were then sterilized for one hour at twenty pounds pressure in an autoclave, after which the sand was inoculated with a small piece of infected green- bean plug upon which Rhizoctonia was growing luxuriantly. In about a month the soil was permeated with the mycelium, and numerous brown sclerotia of various sizes were formed. When smaller amounts of infected soil were needed, a 250-cc. flask was used. No plant was listed as diseased until a pure culture of Rhizoctonia had been isolated from it. Pure cultures were easily obtained by soak- ing small pieces of diseased parts in 1-1000 mercuric chlorid for two minutes and then placing them on green-bean agar. Rhizoctonia developed rapidly, and in twenty-four to forty-eight hours would spread out from the diseased parts. EXPERIMENTS 1 AND IA: INOCULATION OF CARNATION CUTTINGS WITH VARIOUS STRAINS OF RHIZOCTONIA Rhizoctonia is the fungus most commonly found causing a damp- ing-off of carnation cuttings in the greenhouse. To determine whether any of the strains from sources other than carnation are able to attack carnation cuttings with the same ease as those from carnation, the fol- lowing experiment was carried out. Nine hundred carnation cuttings and 28 strains were used in 1913, and 1,725 cuttings and 34 strains in 1914. Sterilized flats (7x10 inches) were filled with sterilized sand; a 250-cc. soil culture of Rhizoctonia was then added to each and the sand tamped down and watered. One flat was left uninoculated to serve as a check. After two days, thirty carnation cuttings (White Enchantress) were planted in each flat, January 2-3, 1913. The flats were then placed in the moist chamber. The inoculated cuttings began to die in about three weeks (Jan- uary 25), and continued dying until the healthy cuttings had rooted, when the experiment was discontinued (February 11) (Fig. 18). The results are given in Table 3. In most cases the cuttings inoculated with the various strains from carnation showed a soft, wet, progressive rot at the callus, which extended in many cases to the surface of the sand. This rot was very characteristic of the attacks of the carnation strains (Fig. 12). At other times the fungus attacked the cuttings just below the surface of the soil, forming lesions of various sizes at the leaf bases. Myce- lium and sclerotia were also formed along the stems and in practically all cases between the leaves just above the soil. 342 BULLETIN ]STo. 189 [June, TABLE 3. — SUSCEPTIBILITY OF CARNATION CUTTINGS TO VARIOUS STRAINS OF EHIZOCTONIA : EXPERIMENTS 1 AND IA Strain Date of isolation Number of plants Experiment 1: 1913 Experiment la: 1914 Healthy | Wilted Dead Healthy Wilted Dead Alfalfa 1910 1912 1912 1913 1913 1913 1911 1911 1911 1911 1911 1912 1912 1912 1912 1913 a. 1912 1913 1912 1912 1913 1912 1911 1912 1912 1913 1913 1913 1913 1912 1913 1913 a 1912 1912 1912 a 1912 1913 1912 a 10 2 3 • 8 0 3 19 6 5 0 0 1 2 4 0 0 '6 0 14 is 7 4 9 9 10 16 3 8 . 4 14 2 1 7 'o 1 11 0 2 2 2 3 3 18 0 0 0 0 6 12 1 2 4 7 6 11 *3 18 26 6 26 26 is 30 26 0 24 23 28 28 26 25 *8 30 30 30 30 10 '6 22 24 17 14 14 3 24 4 0 '2 0 0 33 0 0 0 'a 22 ^4 0 32 0 33 12 0 0 31 18 4 14 0 0 0 0 3 8 0 34 23 24 0 34 24 46 47 '6 0 0 5 0 0 '6 0 9 0 0 O 22 0 0 0 0 0 3 0 2 0 1 0 0 0 0 0 1 0 0 2 0 3 2 *2 1 46 48 48 10 48 48 48 45 17 41 48 14 48 15 36 48 48 14 30 42 34 47 48 48 48 45 40 47 14 25 22 48 11 22 'o 0 Alternanthera E.A.C E AF Aster Bean Beet Besronia Carnation E K » E.O " E.H » E.S " E.2 » E.F " E.M.2 E.107 E.F.2 Carrot Cauliflower Chenopodium Clover Coleus I " II Corn Cotton I " II > > jj j Dianthus barbatus S.M. . N.P.. plumarius sequeri . . Eggplant I . II Lavatera . . . Lettuce Poinsettia Potato E.P.C " E.P.I ' ' E.P.O 5 ' E.Sol Salvia Sedum . . Sugar cane Thistle Check i ) j j "This strain had been in culture for a number of years; the exact year of isolation is not known, 1916] PARASITIC RHIZOCTONIAS IN AMERICA 343 FIG. 18. — EXPERIMENTS 1 AND IA: CARNATION CUTTIN<;S INKKITKD WITH KHI/.IH - TONIA STRAINS (1) CARNATION R.K.; (2) CARNATION R. 107; (3) CAR- NATION R.O.; (4) CARNATION R.F. (5) BEGONIA; (6) COLEUS; (7) POIN- SETTIA; (8) SALVIA; (9) CAULIFLOWER; (10) THISTLE; (11) LETTUCE; (12) POTATO R.P.C.; (13) COTTON; (14) BEAN; (15) POTATO R.P.O.; (16) CARROT 344 BULLETIN Mo. 189 [June, The percentage of infection was about the same with all the carna- tion strains except "Carnation R.O.," which appeared to have lost practically all power of attacking cuttings. This was one of the first strains isolated from carnation. Thus the age of the strain seemed to play an important role in its virulence, and for this reason the date of the original isolation of each strain is included in the table. The strains from alternanthera, coleus, salvia, and poinsettia, all cf which were isolated from diseased plants in the same cutting bench, produced in some cases a soft wet ft)t of the carnation cuttings similar to that caused by the carnation strains. In the majority of cases, how- ever, these strains attacked the cuttings at the callus, forming large brown sclerotia which covered the whole callus and so prevented the formation of roots. Brown strands of the mycelium and sclerotia were formed on all parts of the cuttings underground and also be- tween the leaves. Occasionally, small lesions appeared at the leaf bases which were slightly under the surface of the sand. The two strains from alternanthera and the one from poinsettia killed about the same number of cuttings as the strains from carna- tion, while the one from coleus caused 100-percent infection and rotted the cuttings off faster than the strains from carnation. The percent- age of infection with the strain from salvia was very low. The strain from begonia produced a soft rot somewhat different from that produced by the carnation strains. It appeared on the stem at the surface of the soil and sometimes at the callus. The fungus formed a dense mass of mycelium which completely covered the sand beneath. Here again the virulence was greater than with the carna- tion strains, all the cuttings being killed and in a much shorter time. The strains from eggplant, lettuce, and thistle for the most part formed many sclerotia on the stems and in between the leaves of the cuttings, with only an occasional sclerotium at the callus. Small lesions were found to be abundant at the leaf bases and on the stems. These strains were very weak, especially those from lettuce and thistle, which had been in culture for a number of years. The cuttings infected with strains from cotton, cauliflower, and sugar cane rotted off at the surface of the soil; the rot started as a lesion at this point and progressed very rapidly until the cutting was killed. Smaller lesions were produced on the stem underground. Sclerotia and the brown strands of the fungus could be found in abundance on the parts below the soil. The strains from cotton and cauliflower were very virulent; all the cuttings inoculated with them were killed one week before the cuttings inoculated with a soil culture of the carnation strains began to die off. The potato strains, as a rule, produced a large number of sclerotia and a dark brown mycelium below the soil and on the leaves. The percentage of infection was fairly high and uniform altho the average was below that of the carnation strains. 1916] PARASITIC RHIZOCTONIAS IN AMERICA 345 The strains from alfalfa, bean, and carrot produced symptoms simi- lar to those from potato. A large number of the cuttings placed in the uninoculated sand wilted, but none became diseased. During the spring of 1914, beginning on March 7 and ending on April 7, the experiment was repeated, the only difference being that a number of additional strains were used and flats containing forty- eight cuttings instead of thirty. As will be seen in Table 3, the re- sults were confirmatory. The marked increase in the virulence of the lettuce strain may have been due in part to the influence of tempera- ture both on the strain and on the cuttings. EXPERIMENTS 2 AND 2A; INOCULATION OF YOUNG CARNATION PLANTS WITH VARIOUS STRAINS OF RHIZOCTONIA That the majority of strains can attack carnation cuttings was shown in Experiments 1 and la, where it appeared that the virulence of the strain did not depend on the host from which it was originally isolated, but in some cases did depend on the length of time since the culture was isolated. To determine whether rooted plants were as susceptible to these various strains of Rhizoctonia as were cuttings, further experiments were carried out : Experiment 2 in 1913, involv- ing about 400 young plants and 24 strains; and Experiment 2a in 1914, in which about the same number of plants but only 13 strains were used. Carnation cuttings (White Enchantress) which had been placed in sterilized sand December 12, 1912, were planted February 12, 1913, in sterilized flats (9x12 inches) containing sterilized soil, fifteen plants in each flat. Plants failing to strike root were pulled out, leaving an unequal number in the various flats. The flats were inoculated on March 23 with 250-cc. soil cultures of Rhizoctonia, each flat with a different strain. They were then placed in a case in the greenhouse and left during April and May. Usually the carnation strains, as in the case of the cuttings (Ex- periments 1 and la), produced a soft, wet rot at the surface of the soil or just below. On other plants they caused small lesions of various sizes along the stems, killing the plants slowly. Sclerotia and brown strands of mycelium were as a rule present on plants which showed lesions and on others less badly diseased. Only an occasional plant in the flats infected with other strains than carnation developed a soft, wet rot. In the majority of cases where infection took place the strains produced lesions of various sizes on the stems at the surface of the soil or just below, slowly killing the plants (Fio- 13). As a rule, sclerotia and mycelium were also present on the stems of the infected plants. The plants in the check flat re- mained healthy. 346 BULLETIN No. 189 [June, The resistance of the rooted carnation plants to the fungus, as shown in Table 4, was much more marked than with the cuttings. In the few exceptions the fungus appeared able to infect the plants al- most as readily as it had the cuttings. In 1914 this experiment was essentially repeated. Thirty young car- nation plants (Rosette) were placed in each of a number of flats (12x18 inches) . On April 26, after the plants were rooted, some of the old infected sand from the inoculated flats used in Experiment la was mixed with the soil in which the plaftts were growing. The experiment was continued until June 1. The results, which are presented in Table 4, were similar to those of Experiment 2. As in that experiment, the plants in the check flat remained healthy, with the exception of two that wilted and died from attacks of a Fusarium. TABLE 4. — SUSCEPTIBILITY OF YOUNG ROOTED CARNATION PLANTS TO VARIOUS STRAINS OF RHIZOCTONIA: EXPERIMENTS 2 AND 2A Strain Number of plants Experiment 2: 1913 Experiment 2a: 1914 Total [Healthy | Dead Total Healthy | Dead Alternanthera R.A.C 15 15 12 5 ii 2 i 6 2 0 2 4 13 9 9 2 8 10 'G 13 15 7 8 10 13 12 15 3 10 i 12 13 7 12 15 12 11 '2 6 6 13 7 4 *9 *2 0 7 6 5 2 2 0 30 30 30 30 ^6 30 30 30 30 30 30 30 30 30 18 25 20 15 is io 22 23 13 12 24 19 *24 28 12 5 10 i ii 20 *8 7 17 18 6 11 6 2- R.A.F Amaranth us Beet Begonia 15 14 Carnation R K R.H RS 14 13 14 15 14 15 15 15 15 15 15 14 15 is 15 14 14 15 R.2 RF R.F R.M.2 R.107 R.F.2 Carrot Cauliflower Coleus I Cotton I " II ... " III Dianthus barbatus N.P Eggplant I Lavatera Lettuce Potato R.P.C ' ' R.P.I ' ' R.P.O Salvia Suo-ar cane 15 14 15 Thistle Check » "Killed by Fusarium. 1916] PARASITIC RHIZOCTONIAS IN AMERICA 347 EXPERIMENT 3: INOCULATION OF OLD CARNATION PLANTS IN POTS WITH VARIOUS STRAINS OF RHIZOCTONIA The resistance of young rooted carnation plants to the various strains of Rhizoctonia other than those from carnation was very marked in Experiments 2 and 2a. To determine whether or not old carnation plants were even more resistant, the following experiment was carried out, involving 90 plants and 18 strains. Carnation plants (White Enchantress and White Perfection) were brought in from the field and planted in pots, which were then placed in the bench. The plants were grown under the best possible cultural conditions and on November 27, 1912, when they had become firmly established, they were inoculated. Five plants of the same size were used for each test, one being left as a check. The other four were inoculated by placing a bit of infected green-bean plug near the stem about one-half inch below the surface of the ground. The stems of two plants of each test were slightly wounded before the plugs were placed by them. Observations were discontinued on March 27, four months later. The results are presented in Table 5. Only two plants inoculated by contact died during the course of the experiment, and both were killed by carnation strains. However, where the- stem was slit, the various strains were in most cases able to infect and kill the plant. The check plants remained healthy during the experiment. TABLE 5. — SUSCEPTIBILITY OF OLD CARNATION PLANTS (IN POTS) TO VARIOUS STRAINS OF RHIZOCTONIA: EXPERIMENT 3 Strain Plants inoculated by Check plants Contact Slit Heal thy (Diseased Healthy | Diseased Healthy | Diseased Alternanthera R A F 2 2 2 2 1 1 2 2 2 2 2 2 2 2 2 2 2 2 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 2 1 0 0 0 0 1 0 0 1 2 2 2 2 2 2 1 2 0 1 2 2 2 2 1 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Carnation R.K R.O R.H. R.S R 2 R.F RM 2 " R 107 Carrot • Cotton II Eorp-rjlant I Poinsettia Potato R Sol " RP O . • • • " R P I Thistle 348 BULLETIN No. 189 [June, EXPERIMENT 4: INOCULATION OF YOUNG CARNATION PLANTS WITH ISOLATED AND WITH REISOLATED STRAINS OF RHIZOCTONIA The object of Experiment 4 was to compare the virulence of various strains of Rhizoctonia when they were inoculated on carnation plants for the first time, and after they had been inoculated" on carnation and reisolated. Fifteen strains, taken at random, and about 300 plants were used. On December 12, 1912, a number.of carnation cuttings were made and placed in sterilized sand. They were allowed to remain in the sand until well rooted. On March 22, when the plants were from four to six inches high and breaking nicely, they were placed in three- inch pots in sterilized soil. They were then inoculated by placing a bit of bean pod infected with Rhizoctonia near the stem just below the surface of the soil. Table 6 gives the results obtained. With seven strains the virulence of the reisolated fungus was slightly greater than that of the original isolation. With two it was slightly less. TABLE 6. — COMPARATIVE VIRULENCE OF ISOLATED AND REISOLATED STRAINS OF RHIZOCTONIA WHEN INOCULATED ON YOUNG CARNATION PLANTS (IN POTS) : EXPERIMENT 4 Strain Original isolation Reisolation Health}] Diseased Healthy | Diseased Bean . 9 6 1 4 *5 4 0 3 "(5 6 0 1 0 1 0 0 0 0 9 1 1 2 5 7 4 3 7 5 K) 7 10 8 9 1 y 9 8 5 3 6 7 3 5 0 3 0 2 1 Carnation R K RK R.H 5 6 10 7 RS R.2 RF R F RM 2 4 4 10 9 10 9 10 10 10 10 R.107.. . ... Cauliflower Cotton I • » II . Potato R.P.I . ... Sugar cane Check » > ) EXPERIMENT 5: INOCULATION OF OLD CARNATION PLANTS IN THE BENCH WITH VARIOUS STRAINS OF RHIZOCTONIA Experiment 5 was similar to the preceding experiment except that the carnation plants used were older and were grown in the bench in- stead of in pots, and that inoculations were made with only eight strains of Rhizoctonia, chosen at random. 1916] PARASITIC RHIZOCTONIAS IN AMERICA 349 On September 1, 1913, the soil in two five-foot sections in the green- house was sterilized, and twenty carnation plants from the field were placed in each section, four plants in a row. Four rows in each sec- tion were each inoculated with a different strain of Rhizoctonia, by means of pieces of infected bean plugs. The middle row in each sec- tion was left as a check. The plants began to die off at the end of three weeks and con- tinued dying until the close of the experiment, October 31. They all died in a manner characteristic of stem rot. All the strains used proved to be virulent except the one from beet (see Table 7). The check plants remained healthy thruout the experiment. TABLE 7. — SUSCEPTIBILITY OF OLD CARNATION PLANTS (IN THE BENCH) TO VARIOUS STRAINS OF RHIZOCTONIA: EXPERIMENT 5 Strain (Healthy | Diseased Beet 3 1 Carnation R.107 0 4 Cauliflower 1 3 Cotton II o 4 Dianthus barbatus S,M 1 3 pluniarius 0 4 Eggplant I 1 3 Potato R Sol 1 3 Check 4 0 ) j 4 0 The high mortality of the strains in this experiment was due, to a large extent, to the date of inoculation. The plants in the preceding experiments were inoculated either late in the fall or in the early spring, when the temperature in the greenhouse was low and normal and not influenced by outside conditions. The temperature in the house during September and October, when these plants were inocu- lated, is very high ; hence the virulence of the fungus was much greater. The effects of inoculating plants at various times of the year are clearly brought out in the next experiment. EXPERIMENT 6: INOCULATION OF CARNATION PLANTS WITH RHIZOC- TONIA AT DIFFERENT TEMPERATURES During the season 1913-14 a number of sections containing carna- tions were reserved in the greenhouse, and at different times of the year the plants were inoculated with Rhizoctonia from carnation. This experiment was for the purpose of ascertaining the relative virulence of Rhizoctonia when inoculated on carnation plants at dif- ferent temperatures. Each section contained twenty plants, sixteen of which were in- oculated by placing infected bean plugs at the base of the stem. The remaining four plants served as checks. 350 BULLETIN No. 189 [June, TABLE 8. — EELATIVE VIRULENCE OF EHIZOCTONIA INOCULATED ON CARNATION PLANTS AT DIFFERENT TEMPER \TUKES: EXPERIMENT 6 Section Date of inoculation Experiment discontinued Inoculated plants Check plants Healthy Diseased Healthy | Diseased 143 Sept. 1, 1913 Oct. 1, 1913 1 15 4 0 140 Oct. 1, 1913 Nov. 1, 1913 3 13 4 0 139 Nov. 1, 1913 Jan. 1, 1914 10 6 4 0 138 Dec. 1, 1913 Feb. 1, 1914 8 8 4 0 137 Jan. 1, 1914 Mar. 1, 1914 14 2 4 0 134 Feb. 1, 1914 Apr. 1, 1914? 3 13* 4 0 133 Mar. 1, 1914 May 1, 1914 12 4 4 0 132 Apr. 1, 1914 June 1, 1914 9 7 4 0 131 May 1, 1914 July 1, 1914 0 16 4 0 130 June 1, 1914 July 1, 1914 2 14 4 0 128 July 1, 1914 July 23, 1914 6 10 4 0 aTen plants found infected April 1 ; only three plants died during the months of February and March. As can be seen from Table 8, the death rate of the plants inocu- lated on September 1 and October 1 was almost 100 percent. This rate diminished very markedly when the plants were inoculated later in the season, increasing with the plants inoculated during the spring months until with those inoculated on May 1, it had again reached a high percentage. This condition prevailed during the summer months, showing very noticeably the influence of temperature on mortality. EXPERIMENT?: INOCULATION OF VARIOUS HOSTS. (SEEDLINGS) OTHER THAN CARNATION WITH VARIOUS STRAINS OF RHIZOCTONIA In the preceding experiments all the work was carried on with carnation plants of different ages. It was found that under certain conditions all the strains used could attack these plants, but that the resistance was somewhat increased when the plants were rooted. To determine whether the same results could be obtained with other plants, a number of further experiments were made. Small flats (8x10 inches) were disinfected and filled with a mix- ture of sterilized sand and soil suitable for germinating seed. In each flat a 250-cc. soil culture of one of the various strains used was thoroly mixed with the soil, and the whole allowed to stand for several days. The seeds, after a short soaking in formalin (1-150), were sown in the flats, thirty-one in all, care being taken not to plant them too closely. Nine different kinds of seedlings and 13 strains were used in the ex- periment. The results obtained are given in Table 9. In the first group of the various hosts, clover proved to be more resistant than alfalfa, while the injury to corn roots was negligible. Of the different strains, the one from clover proved the most virulent, while the one from corn was the weakest (Fig. 19). 1916] PARASITIC RHIZOCTONIAS IN AMERICA 351 TABLE 9.— SUSCEPTIBILITY OF VARIOUS PLANTS (SEEDLINGS) OTHER THAN CAR TION TO VARIOUS STRAINS OF BHIZOCTONIA: EXPERIMENT 7 Group 1 Strain On clover On alfalfa On corn Clover 150 seeds Most of seedlings killed at germina- tion; 6 came up; 5 infected below surface of ground, showing lesions ; 1 healthy 150 seeds All seeds attacked by fungus at ger- mination. Rhizoc- tonia present in seeds 30 seeds Plants 4-6 inches high. Seed in all cases showed the presence of Rhi- zoctonia, but whether it would kill the whole Alfalfa About 15 percent damped off in typ- ical manner. Le- sions at surface of ground 80 percent damped off. Others in va- rious stages of in- fection. 5 percent healthy plant is a ques- tion. However, fungus is able .to live in the roots of the corn. Cul- Carnation R. 107. . Only few plants infected. First leaves of a large number dead from effects of fungus 70 percent damped off. Condition sim- ilar to that of plants inoculated with alfalfa strain tures of Rhizoc- tonia were ob- tained from the seeds Corn 2 percent damped off. Rhizoctonia present on the roots of living plants, but did not seem virulent 8 percent damped off. Remaining plants healthy Group 2 Strain On lettuce On eggplant On cabbage Lettuce 150 seeds 90 percent dampec off. Lesions on stem at surface of ground. Leaves also attacked, causing a rot 150 seeds 2 percent damped off. Lesions al surface of ground. Typical 150 seeds Eggplant I 75 percent damped off. Lesions typi- cal, like lettuce 3-4 percent damped off. Typical Thistle 60 percent damped off. Lesions typi- cal, like those on plants inoculated with eggplant strain. Action of fungus slower but virulent 5 percent damped off. Small circular lesions present. Typical Carnation R.F 60 percent damped off. Like thistle; slower in effect, but still virulent All healthy 40 percent infected. Lesions in form of a collar around stem at surface of ground Cauliflower 3 percent damped Only 3 plants off. Typical le- sions healthy. Seedlings attacked at ger- mination 352 BULLETIN No. 189 [June, TABLE 9. — Concluded Group 3 Strain On radish On turnip On beet Radish 150 seeds 150 seeds 100 seeds 1 percent infected at base of stems. Several completely rotted Seedlings attacked at germination. Only 2 healthy plants Potato K.P.C. . . . 15 percent infected at base of stems where root begins. Small wounds like potato scab due to Ehizoctonia • 50 percent damped off. Some rotted off at the ground Carrot Seedlings attacked 50 percent infected. at germination. Only 3 healthy plants All showed collar rot. Some rotted off Carnation R.F. . . 50 percent infected. Lesions at base of stems. Few rotted off 98 percent damped off. Showed collar rot. Typical FIG. 19. — EXPERIMENT 7: UPPER Kow: ALFALFA SEEDLINGS INFECTED WITH EHIZOCTONIA STRAINS (1) CLOVER; (2) ALFALFA; (3) CARNATION R. 107! (4) CORN. LOWER Row: LETTUCE SEEDLINGS INFECTED WITH RHIZOCTONIA STRAINS (1) LETTUCE; (2) EGGPLANT I; (3) THISTLE; (4) CARNATION R.F. Of the seedlings in the second group, lettuce and cabbage were quite susceptible ; eggplant seedlings were very resistant. The strain from cauliflower, altho it caused only a slight damping-off of lettuce 1016] PARASITIC RHIZOCTONIAS IN AMERICA 353 seedlings, produced practically 100-percent infection in the case of cabbage seedlings (Fig. 19). In the third group, beet, radish, and turnip seedlings proved very susceptible to damping-off of Rhizoctonia. It is rather interesting to observe that while the strain from radish was able to cause only 1-percent infection of radish seedlings, it caused almost 100-percent infection of turnip seedlings. Taking the experiment as a whole, it is seen that a great variation exists in susceptibility of seedlings and in virulence of strains. It is clear that under certain conditions all the strains can attack a given host with about the same virulence. EXPERIMENT 8: INOCULATION OF VARIOUS HOSTS (OLD) OTHER THAN CARNATION WITH VARIOUS STRAINS OP RHIZOCTONIA In Experiment 8 the preceding experiment was carried one step farther, older plants being used rather than seedlings. A number of plants were taken from flats while small and transplanted to four-inch pots, where they were allowed to grow for about two months. The soil in these pots was not sterilized. Each plant, with the exception of the check plants, was inoculated by placing an infected bean plug in contact with it just below the surface of the soil. Four kinds of plants, 50 of each, and 12 strains were employed. The observations from this experiment are recorded in Table 10. In Group 1, the tomato plants proved resistant to the attacks of the various strains, with the exception of the one from carnation, which produced a slight infection on two plants. In the case of the cabbage plants, the strains from cotton and from cauliflower exhibited a marked specialization, producing 50- and 90-percent infection, respectively, on these plants, while on tomato plants they produced no infection what- ever. Cabbage was the only host in the experiment susceptible to all the strains with which it was inoculated. The carnation strains in Groups 2 and 3 also proved more virulent than the other strains, producing 50-percent infection on lettuce and 100-percent infection on beet (Fig. 9). Of the other strains, eggplant alone was able to attack the plants, producing a slight infection on two lettuce plants. EXPERIMENT 9: INOCULATION OF VARIOUS HOSTS (CUTTINGS, SEED- LINGS, AND LARGER PLANTS) WITH VARIOUS STRAINS OF RHIZOCTONIA The kinds of plants used in the foregoing experiments were some- what limited. Increased facilities being at hand in the spring of 1914, a more extensive series of inoculations was made with cuttings, seed- lings, and larger plants of various kinds. In all, about 350 cuttings, 3,000' seedlings, and 300 larger plants were inoculated. Thirty-two strains of Rhizoctonia were used. BULLETIN No. 189 [June, B.S^-S J§ a, -S fl w rj (H tj T5 ^ -rH t>^' Iflolf. ^lll£S-! CO rH CD O °° cq §0 se ealthy dise ts htly pl sl ts healthy tly diseased otia and l nd on r ll k plan sligh Scle sma blac pres ft o -IJ-a6 Q n;} CP 5-S.S £ O ,_. •— i - ,-, >•• ft 0 w PARASITIC RHIZOCTONIAS IN AMERICA 355 Flats (9x12 inches) were infected as in Experiment 1, and a vary- ing number of cuttings, seeds, and plants placed in them on March 7, 1914. Pure cultures from the diseased plants in each flat were made! and Bhizoctonia was isolated in each case. Following, the results of the experiment are taken up in detail. "Alternanthera E.A.C." on Alternant her a. —48 cuttings. On March 18 all were dead. The infection \vas first noticed as a small, brown lesion on one side at the surface of the ground; later the lesion girdled the whole stem. The fun- gus also attacked the cut surface of the cutting, causing a lesion and in some instances a slow, wet rot. The mycelium, which grew very profusely, attacked the leaves, producing a characteristic rot. "Alternanthera R.A.F." on Alternanthera. — 48 cuttings. The experiment was carried out exactly like the above and produced the same results. "Alternanthera B.A.F." on Gernanium. — 48 cuttings. These were planted March 20 in the infected flat in which alternant-hero cuttings had died. By May 2, 42 of them were rotted while 6 were rooted and healthy. "Amaranthiis" on Amaranthus salicifolius. — 100 seeds. Seeds germinated March 23, and by April 1 all the plants in the flat damped off in a character- istic manner. "Aster" on Aster. — 100 seeds. Seeds germinated March 18 and a few be- gan immediately to damp off. By April 1, 29 percent had died, while the others remained healthy. "Bean" on Bean. — 30 Feeds. Seeds germinated March 19, and after two months only 5 percent were killed by the fungus. "Beet" on Beet. — 100 seeds. Seeds germinated March 19 and began to damp off. About 25 percent damped off and later about 25 percent more be- came scabby because of the formation of small, depressed lesions. Injury here was similar to the infection of beet by the strains from carnation. "Carnation" on Bean. — 50 plants. On May 8, bean plants about three inches high were transplanted from flats to infected sections (Nos. 157 and 173). The plants took hold readily, and after about two weeks began to show signs of infection. The disease progressed rather slowly; most of the plants produced a few pods before they were killed by the fungus. When pulled up, May 19, every one was diseased or dead (Fig. 8). A detailed description of four typically infected bean plants follows. It will be seen that it corresponds in most details to the descriptions given by Barrus,9 Fulton,43 and Hedgcock60 Plant No. 1: Three distinct lesions were present, one directly above the other on the stem. Lesions were oval in shape with a reddish brown band surrounding a lighter colored sunken area. Evidences were present of young lesions over the entire stem and larger roots under- ground. The wounds extended beneath the cortical layer to the woody tissue. Plant No. 2: Eoots were infected at the joint of their union with the main stem. The lateral root was very badly infected and rotted off entirely. The lesions on the smaller roots were small, depressed, and of a reddish brown color. Plant No. 3 : A large, reddish brown lesion extended from the sur- face of ground downward 2.5 centimeters. Spots were sunken and ex- tended thru the cortex to woody tissue beneath. Two smarl sunken areas of a reddish brown color were present on the stem one inch above the sur- face of the ground. Plant No. 4: A large, depressed, reddish brown area extended from the surface of the ground downward 2.5 to 3 centimeters, almost encircling the stem. Cortical tissue rotted away exposing the woody tissue beneath. "Carnation" on Beet. — 30 plants. On May 8, young beet plants were trans- planted to a section (No. 158) infected with Rhizoctonia from carnation. By 356 BULLETIN No. 189 [June, May 20 they all showed some scab. A number were infected at the crown, where a large number of leaves were completely cut off at the base by the fungus. Sev- eral beets had depressed lesions which extended deep into the tissues. "Carnation" on Cabbage. — 25 plants. On May 8, young cabbage plants were transferred from flats to a section (No. 163) in the greenhouse infected with a soil culture of Khizoctonia from carnation. Some of these plants grew to maturity, but when they were pulled up, May 21, the stems and roots were cov- ered with black, depressed lesions (Fig. 11). Ninety percent of the plants set in the bench were infected in this way. , Where the leaves touched the soil the fun- gus caused a slow, wet rot. "Carnation" on Carrot. — 50 plants. Carrot plants were transferred on May 8 from flats to an infected section (No. 158) in the greenhouse. By May 21 only a few had rotted. The rot started at the crown, where the petioles were attacked, and worked down into the tissues of the root and up into the leaves. The rot from the crown goes into the interior of the root, and thus the root does not show any signs of rot on the outside for some time. Occasionally lesions were found on the sides of the carrots and on the larger roots where they branched from the fleshy part. "Carnation" on Corn. — 10 seedlings. Corn seedlings about 8 inches tall were transplanted on May 8 from flats to an infected section (No. 153) in the greenhouse. The plants grew to maturity. When pulled up, only small lesions were to be found on the roots. These were only slightly depressed and did not retard the growth of the plant. "Carnation" on Eggplant. — 25 plants. On May 8, eggplants were trans- ferred to an infected section in the greenhouse (No. 170). The plants reached maturity with no loss. When they were pulled up, no infection was to be found. "Carnation" on Lettuce. — 60 plants. On March 16, lettuce plants were transferred to an infected section (No. 153). By March 24, 16 percent of the plants were killed. No more loss occurred and the plants were cut on April 21. "Carnation E. 107" on Cabbage. — 100 seeds. Seeds germinated March 19 and began to damp off immediately. By May 21 those which did not damp off were infected in various ways. Some had constrictions just at the surface of the soil; others had definite lesions along the stem and larger roots. Where the plants were crowded, spots of various sizes were formed on the lower leaves which touched the soil. "Carnation E.M.%" on Carrot. — 150 seeds. Seeds germinated March 18. When the experiment was discontinued, May 21, only 10 percent of the carrots were infected at the crown. One showed a constriction which was quite marked. * ' Carnation E.F. ' ' on Beet. — 100 seeds. Seeds germinated March 16 and began to damp off immediately, so that by March 24, 40 percent of the plants were dead. The remainder, when examined on May 21, were all more or less scabby. Some were rotted at the crown. "Carnation E.F. 2" on Bean. — 30 seeds. Seeds germinated March 19. When the experiment was discontinued, May 8, but slight infection could be noticed. "Carrot" on Carrot. — 150 seeds. Seeds germinated March 16. By May 21 only a few of the carrots were infected. An occasional plant showed crown rot, which was especially noticeable at the base of the leaves. "Cauliflower" on Cabbage. — 100 seeds. Seeds germinated March 13. A few seedlings began to damp off March 14 and by May 21 most of the plants were infected. Lesions could be found on the stems, occasionally one girdling the whole stem and forming a sort of constriction as the plant developed. A number of spots varying in size could also be found on the lower leaves which touched the soil. " Cheno podium" on Alfalfa. — 100 seeds. Seeds germinated March 13. Two weeks later 60 percent of the seedlings had damped off in a characteristic manner. "Clover" on Clover. — 150 seeds. Seeds germinated March 12 and began to damp' off slowly. By March 21, however, the plants had reached sufficient size so that no more damping-off occurred. In all about 10 percent of the seed- lings were diseased. 1916] PARASITIC EHIZOCTONIAS IN AMERICA 357 "Coleus I" on Coleus.— WQ seeds. The seeds were all killed by the fun- gus as they were germinating. "Coleus I" on Coleus.— 48 cuttings. By March 18 all the cuttings had rotted off. Infection began as small spots at the surface of the ground or at the callus. Underground lesions of all sizes were produced, from small spots to places where the whole stem was girdled. The leaves of the cuttings were over- run with mycelium, the fungus in many cases rotting them off. "Coleus II" on Chrysanthemum. — 48 cuttings. The old infected flat in which the coleus cuttings had rotted off was planted to chrysanthemum cuttings March 20. By March 27 all of them had rotted off at the surface of the ground. In some a soft, wet rot was produced. "Coleus II" on Coleus. — 100 seeds. Seeds germinated March 24 and began to damp off slowly. By May 21 only 30 percent of the plants were still healthy. "Coleus II" on Coleus. — 48 cuttings. All cuttings rotted off as with " Coleus I." The red-colored cuttings rotted off faster and were much more susceptible than those of the green variety. "Corn" on Corn. — 50 seeds. Seeds germinated March 17. The plants grew to maturity. When pulled up, no signs of infection were noticed. "Cotton I" on Cotton. — 50 seeds. The fungus caused a rotting of the seeds as they germinated. "Cotton III" on Cotton. — 50 seeds. Results same as preceding. "Dianthus barbatus S.M." on Dianthus barbatus (Sweet William).— 100 seeds. Seeds germinated March 19 and began to damp off immediately. By May 22, 50 percent of the seedlings were diseased. "Dianthus barbatus N. P." on Dianthus barbatus (Sweet William). — 100 seeds. Results same as preceding. "Dianthus plumarius" on Dianthus plumarius. — 100 seeds. Seeds germinated March 14. By May 22, 80 percent of the plants had damped off. "Dianthus sequeri" on Dianthus sequeri. — 100 seeds. Seeds germinated March 18 and began to damp off immediately. By May 22 only about 25 percent were still healthy. "Eggplant I" on Eggplant. — 150 seeds. Seeds germinated March 23. By May 8 only 3 to 4 percent of the plants had damped off. "Eggplant II" on Eggplant. — 150 seeds. Seeds germinated March 23. The fungus caused a rot of the seeds at germination. " Lavatera" on Lavatera trimestris. — 100 seeds. Seeds germinated March 12. By May 22 about 25 percent of the seedlings had damped off (Fig. 14). On the remainder, lesions of various sizes were present, which in some cases girdled the stem just below the surface of the soil and formed a collar, or constriction. "Lettuce" on Lettuce. — 125 seeds. Seeds germinated March 13. By April 1 all the young plants had damped off. "Poinsettia" on Euphorbia variegata. — 100 seeds. Seeds germinated March 23. By May 22, 6 percent of the plants had damped off. " Salvia" on Salvia splendens. — 100 seeds. Seeds germinated March 23. By May 8, 6 percent of the seedlings had damped off. By May 21, 4 of the plants were infected. Lesions extending into the woody tissues were present on the stem. "Salvia" on Salvia splendens. — 48 cuttings. These cuttings rotted off very rapidly. Wherever the leaves touched the soil, they were rotted also. By April 7, 41 cuttings were diseased and 7 were rooted and healthy. "Sugar Cane" on Amaranthus salicifolius. — 100 seeds. Seeds germinated March 23. On May 21 all the plants were' perfectly healthy. No infection was present. "Thistle" on Clover. — 100 seeds. Seeds germinated March 13. On May 21 all the plants were healthy. Additional Inoculations.— On April 1 six flats of infected soil used in the inoculation experiments with carnation cuttings were mixed with soil in larger flats and four hills of potatoes were planted in each. The six flats represented the 358 BULLETIN No. 189 [June, six strains ' ' Alternanthera B.A.F.," "Carnation K.F., " "Cauliflower," "Let- tuce/' "Cotton," and "Dianthus barbatus. " Only one or two potato sprouts came up from each hill and these were weak and spindling. After the tempera- ture became too high in the greenhouse, the flats were placed outside, so that the plants would develop further and produce tubers. The strains killed some of the young sprouts and dwarfed the others, showing that they were able to attack the potato plant. Here, as in the preceding experiments, the death rate of the vari- ous plants was quite variable. These differences appear to be due to the virulence of the fungus, to the susceptibility of the plant, or to a combination of factors. EXPERIMENT 10 : INOCULATION OF VARIOUS HOSTS IN THE FIELD WITH VARIOUS STRAINS OF RHIZOCTONIA All the inoculation experiments reported so far were conducted in the greenhouse. In the summer of 1914 a fourth of an acre of land was divided into three parts, separated by six-foot strips of ground. Sec- tion 1 was inoculated on May 20 with twenty cubic feet of infected soil taken from the inoculated benches in the greenhouse. The soil was spread upon the section, worked under, and watered for several days. Section 2 was left as a check. In Section 3 small bits of pure cultures of various strains of Rhizoctonia were added with the seeds and plants. The seeds were planted May 20, and the young plants were put in June 16. Altho the drouth of the summer interfered considerably, the results obtained were sufficient to show that RJiizoctonia Solani was active under field conditions as well as in the greenhouse. No infection occurred in the first two sections. In Section 3 in- fection was quite marked in a number of cases, especially on cotton, potato, and several greenhouse plants. Where the strain ' ' Cotton I ' ' was added to the cotton seeds, 100-percent infection occurred. In the case of potato, to which ' ' Carnation R.F.2 ' ' was added, a marked dif- ference was noticed, the plants in this section being dwarfed and spindling, while in the first two sections they were bushy and strong. The difference in the yield was as marked as the difference in growth of the plants. All the coleus plants infected with "Coleus I" were killed within two weeks after being set out. The same results were obtained from inoculating salvia plants with the strain from salvia. DISCUSSION OF INOCULATION EXPERIMENTS In Table 11 are brought together, in tabular form, the results of all the inoculation experiments, with the exception of No. 4, which was carried on primarily to test the comparative virulence of isolated and reisolated strains of Rhizoctonia. The thing that stands out at first glance is the great variation in the mortality of the plants when inoculated with strains from the same host and when inoculated with strains from other sources. 19161 PARASITIC RHIZOCTONIAS IN AMERICA 359 When carnation cuttings were infected, the strains used, with but two exceptions, whether from carnation or from other hosts, were able to cause more or less loss, the mortality of the cuttings ranging in either instance from 0 to 100 percent. Again, the same strains varied in virulence from one year to another, in most cases decreas- ing in virulence with age. When cuttings other than carnation were used, the results were the same. When young rooted carnation plants were inoculated, the percent- age of loss was much less than with cuttings. Here, however, the car- nation strains seemed to be slightly more virulent than those from other sources, altho there was still a great difference in the strains from carnation themselves. Only one of the strains from other sources was unable to attack young rooted carnation plants. On old carnation plants in the greenhouse which were inoculated by contact, even the carnation strains did not cause a high percentage of infection. However, when plants growing under these same condi- tions were slightly wounded and then inoculated, the percentage of loss was very high in nearly all the strains studied. When conditions (temperature and moisture) were favorable to the fungus, most of the strains studied were able to infect carnation plants as readily as the carnation strains themselves. In the majority of cases all strains were able to cause damping-off of various seedlings. There was a great difference in the virulence of strains when inoculated on the same host from which they had been isolated and when inoculated on other hosts. Only occasionally was there any indication of marked specialization, and in no case was such indication corroborated in succeeding experiments. In older plants, a marked difference in susceptibility was found in the different species. As a rule, the root crops were highly susceptible to attacks of Rhizoctonia. Among these, beet appeared to be the most susceptible. Tomato and eggplant showed a very marked resistance to Rhizoctonia, and this was true to some extent of the potato also, altho under certain conditions it was quite susceptible. This varia- bility of resistance held true for most of the vegetable and field crops other than root crops. Under ordinary conditions, the majority of floricultural plants were not subject to attacks of Rhizoctonia, altho the mycelium of this fungus was known to be present in the soil or even on the plant itself. From the fact that all the strains studied showed the ability to attack the same species of plant and produce the same characteristic symptoms, it seems clear that they can be included under one form, R. Solani. These experiments show further that the virulence of R. Solani is very variable, as is also the degree of resistance of the vari- ous host plants, both depending on a number of varying factors. 360 BULLETIN No. 189 [June, TABLE 11. — SUMMARY OF INOCULATION EXPERIMENTS Strain Original date of isolation Date of inoculation experiment Host Condition Per- centage of loss" Alfalfa 1910 1912 1912 1913 1913 1913 1911 1911 1911 1911 1911 1913 1913 1 1913 1913 1913 1913 1914 . 1913 1914 1913 1914 1913 1914 1913 1914 1913 1913 1914 1914 1914 1914 1914 1914 1914 1913 1914 1914 191-4 1914 1913 1913 1913 1913 1913 1913 1913 1913 1913 1913 1913 1914 1914 1913 1913 1913 1913 1913 1913 Alfalfa Cabbage Carnation Clover Corn Tomato Alternanthera Carnation ) > ) j Alternanthera Carnation j > t ) j > > > » Geranium Amaranthus salicifolius Carnation j > Aster Carnation Bean Carnation i > Beet Carnation > f > > j ) > j > j j > r > j t j j Seedlings Plants Cuttings Seedlings ) j Plants Cuttings t > 11 Young plants Cuttings > j )t Young plants > ) » Old plants » j > (wounded) Cuttings Seedlings Cuttings Young plants Seedlings Cuttings Seedlings Cuttings > j Seedlings Cuttings Young plants Old plants Cuttings Young plants Cuttings Young plants Old plants > } r > (wounded) Cuttings Old plants » » (wounded) Cuttings » Young plants Old plants 1 1 > > (wounded) Cuttings Young plants Old f ) t > (wounded) 95 20 38 15 0 0 100 92 96 20 100 90 100 66 40 0 50 87 100 100 16 29 23 5 65 100 50 100 33 25 100 6 90 85 0 100 0 0 100 80 100 50 0 100 82 93 50 100 Alternanthera R.A.C. Alternanthera R.A.F. Amaranthus Aster Bean Beet Begonia Carnation R K Carnation R O Carnation R H Carnation R.S "In Experiments 1 and la the loss from plants wilted is not included in the percentage of loss. 1916] PARASITIC RHIZOCTONIAS IN AMERICA 361 TABLE II.— Continued Strain Original date of isolation Date of inoculation experiment Host Condition Per- centage of loss' Carnation R 2 1912 1913 I/&I*H&ijlOU p *f i r\f\ 1UU 1913 " Young plants 54 1913 ' ' Old plants 50 1913 " " » Carnation R F 1912 1913 Rppf (wounded) 100 Ofi -t>t?t; u beedlings \JO 1914 ' ' " 40 1913 Cabbage " MO 1913 Carnation Cuttings 100 1914 " " 94 1913 Young plants 85 1913 " ' ' 100 1914 j ) » 50 1913 Old plants 0 1913 )) ) j (wounded) 100 1913 Eggplant Seedlings 0 1913 Lettuce j > 60 1913 ft Plants 50 1913 Radish Seedlings 50 Carnation R.M.2 .... 1912 1913 Carnation Cuttings 96 1914 } > j t 43 1913 ' ' Young plants 85 1913 } ' Old plants 0 1913 ' ' > ) )) (wounded) 50 1914 Carrot Seedlings 10 Carnation R.107 1912 1913 Alfalfa 9> 70 1913 Beet Plants 100 1914 Cabbage Seedlings 75 1913 Carnation Cuttings 92 1914 " 1 ' 91 1913 i > Young plants 73 1913 " Old plants 0 1913 * ' j j ) > (wounded) 100 1913 ' ' Old plants 100 1913 Clover Seedlings 5 1913 Corn " 0 Carnation R F 2 1913 1914 Bean > t 3 1914 Carnation Cuttings 100 1914 " Young plants 66 Carnation R. 12 1-5. .. 1912 1913 Cabbage Plants 70 1913 Tomato " 20 Carnation (Sections 157 and 173) 1914 Bean " 98 Carnation (Section 158) 1914 Beet »i 95 ( 163) 1914 Cabbage > » 90 " ( 158) 1914 Carrot t j 10 V *w» y " ( 153) 1914 Corn Seedlings 0 V *w i ( 170) 1914 Eggplant Plants 0 ( 153) 1914 Lettuce " 16 'See footnote, page 360. 362 BULLETIN No. 189 \June, TABLE 11. — Continued Strain Original date of isolation Date of Inoculation experiment Host Condition Per- centage of loss" 1913 Beet Plants 0 1912 1913 1914 1913 1913 1913 1914 1913 1913 1913 Carnation > } ) ) ) ) } ) ^Carrot Radish Turnip Cabbage Cuttings ) t Young plants Old plants j ) ft (wounded) Seedlings » > > ) ) 66 30 13 0 0 5 98 50 98 1913 1914 1913 1913 1914 1913 1914 1913 1913 1913 1914 j j ) ) Carnation ) } > ) ) t ) > Lettuce Tomato Alfalfa > ) Plants Cuttings ) ) Young plants ) ) ) ) Old plants Seedlings Plants Seedlings 97 90 100 100 40 26 75 3 0 60 Clover 1912 1914 1913 Carnation Alfalfa Cuttings Seedlings 31 100 Coleus I 1912 1914 1913 1914 1913 1913 Carnation Clover y ) Corn Carnation Cuttings Seedlings 9t ) ) Cuttings 75 99 10 0 100 Coleus II 1913 1914 1913 1914 1914 1914 1914 ) ) > ) ) > Coleus ; ) Carnation it Young plants ) y t ) Seedlings Cuttings } ) 100 40 23 100 100 100 1912 1914 1914 1914 1913 Chrysanthemum Coleus ; ) Alfalfa ) > Seedlings Cuttings Seedlings 100 70 100 8 Cotton I 1911 1914 1913 1913 1914 1913 Carnation Clover Corn ) ) Cabbage Cuttings Seedlings > > ) ) Plants 51 2 0 0 50 Cotton II 1912 1913 1914 1913 1914 1914 1913 1913 Carnation ) ) > > ) ) Cotton Tomato Carnation Cuttings ) > Young plants » }> Seedlings Plants Cuttings 100 62 87 56 100 0 100 Cotton III . 1912 1914 1913 1913 1913 1913 1914 > j tt ) ) t ) } > ) 7 j ) Young plants Old plants 19 >r (wounded) Old plants Cuttines 91 46 0 50 100 70 •See footnote, page 360. 1916] PARASITIC BHIZOCTONIAS IN AMERICA 363 TABLE 11.— Continued Strain Original date of isolation Date of inoculation experiment Host Condition Per- centage of loss" Cotton III .... 1912 1913 0 & r n ci t i o 11 V 1 oc 1914 Cotton Seedlings 00 100 Dianthus barbatus g M 1913 1914 Carnation Cuttings 98 1913 Old plants 75 1914 Dianthus barbatus Seedlings 50 Dianthusbarbatus N.P. 1913 1914 Carnation Cuttings 100 1914 " Young plants 60 1914 Dianthus barbatus Seedlings 50 Diauthus plumarius . . 1913 1914 Carnation Cuttings 100 1913 " Old plants 100 1914 Dianthus plumarius Seedlings 80 Dianthus sequeri 1913 1914 Carnation Cuttings 100 1914 Dianthus sequeri Seedlings 75 T*1o*otinlp'ni" T 1912 1913 Carnation Cuttinsrs 42 1914 " " 93 1913 j > Young plants 60 1914 } ' > ) ) > 20 1913 J 7 Old plants 0 1913 ) ) } j » (wounded) 100 1913 " Old plants 75 1913 Eggplant Seedlings 3 1914 » " 4 1913 Lettuce » 75 1913 ) > Plants 20 Eggplant II 1913 1914 Carnation buttings 83 1914 Eggplant Seedlings 100 Lavatera 1913 1914 Carnation Cuttings 98 1914 Young plants 36 1914 Lavatera trimestris Seedlings 95 1913 Carnation Cuttings 0 1914 " >' 34 1913 j > Young plants 13 1913 " Old plants 0 1913 " " " (wounded) 100 1913 Eggplant Seedlings 2 1913 Lettuce j ) 90 1914 " " 100 1913 99 Plants 0 Poinsettia . . 1912 1913 Carnation Cuttings 75 1914 ) ) ) r 52 1913 ) ) Old plants 0 1913 » ) f > ) (wounded) 100 1914 Euphorbia variegata Seedlings 6 Potato E P C .... 1912 1913 Beet " 50 1913 >i Plants 0 1913 Carnation Cuttings 90 1913 j j Young plants 0 "See footnote, page 360. 364 BULLETIN No. 189 [June, TABLE 11. — Concluded Strain Original date of isolation Date of inoculation experiment Host Condition Per- centage of loss* Potato E.P.C Potato E P I , 19.12 1912 1913 1913 Radish Carnation Seedlings Cuttings 15 65 Potato K.P.O 1913 1913 1913 1913 ; ) ) ) Young plants Old plants it tf (wounded) Cuttings 50 0 100 KQ Potato R. Sol 1913 1913 1913 1913 ) ) > 1 ) Young plants Old plants ) j ) i (wounded) Cuttings 43 0 50 fiO Radish • • 1913 1913 1913 1913 ) ; ) > i ) Roof Old plants » j> (wounded) Old plants Plants 0 100 75 Salvia 1Q19 1913 1913 1913 Radish Turnip Seedlings ) > 1 99 Sedum 1Q1 1 1914 1913 1914 1914 1914 y y > > Salvia splcndcns )) Young plants Seedlings Cuttings )> 47 33 10 85 1 no Sugar cane Thistle 1912 1914 1914 1913 1914 1913 1Q1 T j j Amaranthus salicifoliux Carnation 7 ) ) ) > Young plants Seedlings Cuttings j i Young plants 20 0 90 24 13 Q9 1914 1913 1913 19J3 1914 1913 1913 1914 1 J ) Clover Eggplant Lettuce > ) y ) Young plants Old plants > j j ) (wounded} Seedlings j > it Plants 47 14 0 100 0 5 60 0 "See footnote, page 360. GROWTH ON MEDIA In the course of these studies thirty-eight strains of Rhizoctonia were grown on five of the more common vegetable-extract agars and a solid synthetic medium. The composition of these media may be found in the appendix, together with a complete description of the growth of the various strains on them. 1916] PARASITIC KHIZOCTONIAS IN AMERICA 365 As a rule the fungus isolated from carnation plants, when grown on green-bean agar, produced a rapid-growing mycelium, which was practically all aerial, loose, and tufted. The most characteristic fea- ture was the production of concentric zones, tho this was not invaria- ble. Of the many hundred cultures made during the past three years from diseased carnation plants on green-bean agar, 90 percent have shown this zonation. This characteristic was influenced by neither light nor temperature. A typical growth on this medium is shown in Fig. 20, "Carnation R.H." A few of the carnation strains grown on the same medium and showing the same type of mycelium produced very indistinct zonation or none, as shown in Fig. 20, "Carnation R.F." Zonation persisted to some extent when the carnation strains were grown on other media than green-bean agar, but it was not so characteristic. The two strains from potato did not grow so rapidly nor quite so luxuriantly on green-bean agar as did the carnation strains, but they produced the same even, tufted, zonate growth. Here the zones were closer together. (See Fig. 20, "Potato R. Sol.") The growth of the strain from corn on green-bean agar was similar to that of "Potato R. Sol." The growth on green-bean agar of the strains from eggplant, let- tuce, Chenopodium, and thistle was different from any of the other forms in that the mycelium grew along the surface, running out ra- dially in strands, which became larger and more tufted at the edge. (See Fig. 21, "Eggplant I. ") The strains isolated from alternanthera, coleus, salvia, and poin- settia, when grown on green-bean agar, showed the same even, fluffy to tufted growth. This was also characteristic of the strains from cauliflower, cotton, and sugar cane. Zonation in these strains was varied. (See Fig. 21.) The strain from onion when grown on this agar differed radi- cally from the others. The mycelium was bright colored, finer, and almost all submerged. (See Fig. 20.) The other strains studied on green-bean agar cannot be put in definite groups, as they shade into one another. However, the growth of the mycelium was somewhat similar in each case ; practically the only difference noted was in the extent of the zonation. On corn-meal agar the growth of the strains was similar to a large extent; the only great difference noted was in rapidity of growth. Zonation was very rare on this medium. The growth of the strains on oat agar was somewhat variable; zonation was sometimes present and sometimes absent. The most characteristic feature of the growth of the majority of the strains on potato agar was the turning brown of both the myce- lium and the medium. This same characteristic, but to a less degree, 366 BULLETIN No. 189 [June, FIG. 20. — CULTURES OF EHIZOCTONIA STRAINS SHOWING DEVELOPMENT OF MYCE- LIUM ON GREEN-BEAN AGAR (CULTURE 48 HOURS OLD). TOP Row: (1) CAR- NATION E.H.; (2) CARNATION R.F. MIDDLE Row: (1) POTATO R. SOL.; (2) CARROT. BOTTOM Row: (]) CAULIFLOWER; (2) ONION 1916] PARASITIC RHIZOCTONIAS IN AMERICA 367 FIG. 21. — CULTURES OF KHIZOCTONIA STRAINS SHOWING DEVELOPMENT or Mv< K LIUM ON GREEN-BEAN AGAR (CULTURE 48 HOURS OLD). TOP Row: (1) ALTER - NANTHERA R.A.F. ; (2) ALTERNANTHERA R.A.C. MIDDLE ROW : (1) POIN- SETTIAJ (2) COLEUS I. BOTTOM ROW : (1) EGGPLANT I; (2) LETTUCE 368 BULLETIN No. 189 [June, FIG. 22.— CULTURES OF RHIZOCTONIA STRAINS SHOWING DEVELOPMENT OF SCLERO- TIA: (1) ALTERNANTHERA R.A.C.; (2) SALVIA; (3) POINSETTIA; (4) ALTER- NANTHERA R.A.F. ; (5) COLEUS ; (6) EGGPLANT II; (7) EGGPLANT I; (8) LETTUCE; (9) CHENOPODIUM; (10) THISTLE; (11) CARNATION R.F.2; (12) CARNATION R.S.; (13) CARNATION R.2; (14) CARNATION E.H.; (15) CARNA- TION R.O.; (16) ASTER; (17) COTTON I; (18) BEET; (19) CARROT; (20) BEAN 1916} PARASITIC RHIZOCTONIAS IN AMERICA 369 FIG. 23. — CULTURES OF EHIZOCTONIA STRAINS SHOWING DEVELOPMENT OP SCLEKO- TIA: (1) AMARANTHUS; (2) PANSY; (3) LAVATERA;(4) SWEET ALYSSUM; (5) LOBELIA; (6) ALFALFA; (7) CLOVER; (8) CORN; (9) CAULIFLOWER; (10) SUGAR CANE; (11) BUCKWHEAT; (12) RED CLOVER; (13) SEDUM; (14) GYPSOPHILA; (15) ONION; (16) DIANTHUS BARBATUS S.M.: (17) DIANTHUS PLUMARIUS; (18) DIANTHUS SEQUERI; (19) DIANTHUS BARBATUS N.P.; (20) ASTER (CARNATION STRAIN) 370 .BULLETIN No. 189 [June, was found with the growth on potato-glucose agar. On both these media zonation was usually lacking or indistinct. On Agar XII most of the strains grew rather poorly and produced a white, flaky growth, with varying zonation. Early in the study of the characters of the strains on culture media, it was noticed that as there were characteristic differences in growth, so also were there differences in the production of sclerotia. The strains "Eggplant I," "Lettuce," " Chenopodium, " and "Thistle" on green-bean agar all iormed sclerotia in a characteristic manner. The sclerotia were white at first and flat, later turning black, and as the culture became older, curling up and becoming crust-like. All four of the forms mentioned above showed these same character- istics, altho they were originally obtained from widely separated locali- ties. (See Fig. 22.) The strain from onion produced sclerotia which were entirely different from those of other strains in that they were small (.5 to 1 millimeter in diamater), perfectly round, bright colored, and developed submerged in the medium. (See Fig. 23.) The strains "Buckwheat," "Carnation R.O.," " Gypsophila, " and "Sedum" rarely produced sclerotia in culture. Kepeated observations showed that this loss of power to produce sclerotia was the first sign of the de- generation and loss of virulence of the strain. All the other strains studied produced sclerotia which were at first white, later becoming brown. Altho the sclerotia from the strain from potato are similar to those from carnation when grown on culture media, on the potato tuber they are entirely different. For the most part the Khizoctonia sclerotia on potato tubers which the writer has examined are flat and hard, have a black luster, and are in many re- spects like the sclerotia produced in culture media by the strains from eggplant, lettuce, etc. The only conclusion that can be drawn from this study of the growth of Khizoctonia Solani on media is that the strains are very variable, those from the same host often producing a different growth, even? on the same media, and that the differences in various cultural characters which are shown by strains from different hosts are no greater than differences which may be manifested by two different strains isolated from the same host or by the same strain at different ages. MEASUREMENT OF MYCELIAL CELLS It was rather difficult to choose a standard in the measurement of the mycelial cells, because the cells varied in size at different ages and on different media. Finally the following standard was chosen: Hyphae from the outer edge of a twenty-four hour old culture on green-bean agar were selected at random. The length and width of a cell from which the branch arose nearest the tip of the hypha, and 1916] PARASITIC RHIZOCTONIAS IN AMERICA 371 the distance on the inner side from the parent hypha to the first sep- tum of the branch, were measured. Ten cells df each strain were measured, and the averages of these measurements used for compari- son. As shown in Table 12, the measurements varied considerably, and this was true even with strains from the same host. In the three car- nation strains measured, the length of the mycelial cells varied from 70/x to 181.7^', a difference of 111.7^. However, the average of ten measurements brings the difference down to some extent. A still more striking difference was noted in the strains from Dianthus, where the smallest reading was 50/x and the largest 215/x, a difference of 165/x. Similar differences were also found in comparing the two other meas- urements. In all cases, altho the table does not bring out this point, different measurements of the cells of the various strains overlapped. For ex- TABLE 12. — MEASUREMENTS OF MYCELIAL CELLS OF EHIZOCTONIA Strain Length of cell Width of cell Distance from cell to septum of branch Alfalfa 152.04 113.40 124.60 107.80 180.04 77.92 116.09 141.40 128.15 116.64 119.64 175.56 88.20 117.60 133.28 101.64 65.24 113.12 161.00 131.60 166.95 132.34 148.88 122.08 91.84 119.92 126.20 111.16 90.80 113.12 130.48 138.08 0 5.76 3.92 4.94 4.83 6.57 4.34 4.59 5.60 5.19 4.42 4.20 5.43 5.32 5.04 4.97 4.39 5.50 5.58 5.27 6.29 5.65 4.20 5.60 3.55 5.89 4.39 3.44 5.01 4.48 4.09 5.04 4.62 j* 10.08 6.72 9.32 7.98 13.08 6.52 10.83 10.49 10.92 9.60 9.60 11.20 8.53 10.21 10.22 9.24 10.18 9.44 10.58 6.44 13.44 11.65 9.57 8.03 9.18 10.54 7.92 9.93 7.00 6.57 8.54 11.48 Alternanthera R A.C " RAF Beet » R M 2 » RF.2 Cauliflower Chenopodium Clover Coleus II Cotton 1 N P plurna/rius n ii'i Salvia SsduiTi Thistle 372 BULLETIN No. 189 [June, ample, while the average length of a cell from " Cotton I" was only 65/t, the largest reading was 127. 5/x, which was higher than the small- est measurement of a cell of the strain ' ' Chenopodium, ' ' whose aver- age reading was 110/x higher than that of "Cotton I." If measure- ments are made of hyphae forty-eight hours old, the differences are still more striking, even in the same strain. Hence, on the measurement of mycelial cells of RMzoctonia Solani, as on the study of the growth on media, no conclusions can be based in regard to distinguishing the strain* of this difficult species. SOIL SURVEY OF RHIZOCTONIA As shown in Table 1, RMzoctonia Solani has been observed in al- most every state in the Union, and causes injury to a large number of plants under various conditions and in widely different types of soils. To determine to how great an extent Rhizoctonia is actually present in the soil, several surveys were made at the University of Illinois in fields containing a variety of plants. Survey of the Perennial Garden, Horticultural Grounds, April 28 to May 1, 1914. — During the summer and fall of 1913, Rhizoctonia was isolated from a number of perennial plants in the garden. To determine whether the fungus lived on the dead parts of the plants or in the soil or both during the winter season, a survey was made the following spring. Since it is somewhat difficult to isolate Rhizoctonia directly from the soil by means of soil cultures, the following method was devised to determine its presence in the soil : Small patches of ground were selected over the field about twenty feet apart, so that the results might give a fair idea of the distribution of the fungus. Each space was cleared except for a small living plant, and the soil thoroly watered. Three sheets of moistened filter paper were then placed on the ground over the plant. To prevent evaporation, a small flat with a layer of wet moss attached to the bottom was placed over the paper. The flats had previously been sterilized in formalin (1-100) and the moss sterilized in the autoclave. Thru several small holes in the bot- tom of the flat, water was added to the moss from day to day to keep it moist. At the end of the fifth day the plant parts were removed to the laboratory. The presence of the fungus was determined by means of pure cul- tures and by microscopic observation. Where the identification de- pended solely on microscopic observations, the material was left in a covered dish for several days until the strands of the fungus became older, when they could be distinguished more readily by their color. In thirteen cases out of sixteen Rhizoctonia was found present on the dead or living pieces of plants placed in contact with the soil ; 1916] PARASITIC RHIZOCTONIAS IN AMERICA 373 ra * Li CJ I 'CL p w JH O> 0? -*i •a ft ^2 JS Pn ^ <2 < . .1 s | 'o> I-: °^ _-^ C § §.2 § J !§!!£! ^^.2 1 374 BULLETIN No. 189 [June, hence we may conclude that this fungus was very abundant both in the soil and on the plant parts in contact with the soil. Survey of Plot Used for Field Inoculation Experiments, May 6 to May 11, 1914.— -This plot, formerly used by the Agronomy Depart- ment, had been under cultivation for a number of years. The pre- vious season the field had been in potatoes and corn. The old potato stalks were left scattered over the field during the winter. A survey of the plot was made before plowing, following the same method as was used as in the preceding experiment. Sixteen flats were set out twenty-five feet apart. After five days an examination for the presence of Rhizoctonia was made. By microscopic examination and pure cultures, Rhizoctonia was detected in ten trials out of sixteen on this plot. Survey of Agronomy Plots on Xortli Farm, September 26 to Octo- ber 2, 1914. — Here a more extensive survey was conducted. The agronomy plots on the North Farm were chosen for this purpose be- cause of the fact that they had been under continuous cultivation since 1895, and showed the effects of different methods of soil treat- ment, various systems of crop rotation, and the application of differ- ent kinds of food. (For treatments and rotations used, see Fig. 24.) These plots are also typical of the prairie soil, which represents the most extensive and important type of soil in Illinois. The procedure followed in this survey was modified as follows: Instead of a flat, a seven-inch flower pot, which could be easily steri- lized and dried, was employed. Small cheesecloth bags were filled with sphagnum moss; these were sterilized in the autoclave. When ready for use, the bags were moistened and placed in the bottom of the pots and secured in such a way that they remained in position when the pots were inverted. A small patch of soil, one in each plat, was lev- eled off, only a small living plant or some plant debris being left. Several thicknesses of moistened filter paper were then laid over the spot, and a flower pot was placed over the whole. The pot was pushed into the ground about three inches and the soil heaped up around it on the outside. The pots were left in this condition about one week, during which time the moss was moistened at intervals. Conditions were very favorable to the growth of Rhizoctonia if it was present in the soil. When the pots were lifted, the plant parts or debris with some of the soil were wrapped in the filter paper and placed under bell jars. The contents of the papers were then examined for the presence of Rhizoctonia. These plots showing the effects of diverse treatments yielded R. Solani in sixty-four trials out of seventy. The six negative results were scattered over the field, so that no correlation between the treat- ment of the plot and the presence of Rhizoctonia can be said to exist. 1916] PARASITIC RHIZOCTONIAS IN AMERICA 375 The results of these experiments admit of no question as to the presence of the fungus Khizoctonia Solani in the soil in the vicinity of Uj-bana. PARASITISM OF RHIZOCTONIA SOLANI KUHN That R. Solani is an active parasite under certain conditions would never be questioned by anyone who had seen a severe attack of car- nation stem rot in the field or greenhouse. In the cutting bench this fungus causes damping-off of cuttings in an incredibly short time, while seedlings damp oft' almost as fast. At times Rhizoctonia causes considerable loss in potato fields. In fact, it may become epidemic and cause serious injury to most of the field, vegetable, and floricul- tural crops. The epidemics are apparently due to a combination of factors, such as the presence of a virulent strain of the fungus, a susceptible variety of plant, and optimum conditions of temperature and moisture for infection and development. Under ordinary conditions most of the strains appear to be weak parasites. The apparently universal presence of Rhizoctonia in the soil, where it can live indefinitely on dead organic matter under ordinary conditions, makes it a dangerous fungus. The fact that it shows no marked specialization and can attack a large variety of weeds assists in harboring the fungus and in keeping up its virulence. The sclero- tia and mycelium can live under adverse conditions for several years. Transfers from soil cultures started in December, 1911, kept in the laboratory, and allowed to dry out, yielded pure cultures as late as July, 1914. Soil cultures left in the field during the entire winter yielded the fungus in the spring. In all but one of the experiments inoculation was brought about without wounding the plants in any way, in many cases the fungus being simply mixed with the soil in which the plants were growing. The results furnish convincing proof of the parasitism of the fungus. The conditions under which all strains manifested their greatest para- sitism were primarily a high temperature (above 88° F.) and a soil moisture content either too low or too high for the best development of the plant. When carnation plants growing in soil inoculated with Rhizoctonia were given a heavy watering and the soil was then allowed to dry out, they were killed more rapidly than plants growing under the same conditions but in continually over-watered soil. Plants watered normally died off slowly and the percentage of loss was very much less. Repeated observations in greenhouse and field have shown certain amount of the mycelium must be present before the fungus able to attack and kill the plant. A small amount of mycelium has always been observed around a carnation plant in the bench a week 376 BULLETIN No. 189 [June, or more before the plant showed any signs of being diseased. In fact, a certain amount of mycelium is always present in the carnation soil in the greenhouse, but it is only when the temperature is high that the fungus is able to attack the plants. This explains why stem rot of carnations is more severe during the summer months than in the winter. (See Experiment 6, page 349.) In the field similar conditions are necessary to result in infection of a plant. Investigations to determine how much vigor the mycelium must attain before the fungus can attack a plant are now in progress, as is also a histological and enzymatic study. SUMMARY 1. At the present time there are recognized in America two species of truly parasitic Rhizoctonias : The common form, Rliizoctonia Solani Kiihn (C6rticium vagum B. & C.), widely distributed and oc- curring on a great number of hosts; and R. Crocorum (Pers.) DC., with a limited distribution on alfalfa and potato tubers. A third Rhizoctonia, Corticium ocliraleucum (Noack) Burt, is found on the leaves of pomaceous fruit trees, while a fourth species isolated from damped-off onion seedlings is of questionable parasitism. 2. The plants thus far listed as more or less subject to attacks of RJiizoctonia Solani Kiihn in the United States number about 165 species. All the more important families of dicotyledons are included in this list, as well as a number of monocotyledons, several gymno- sperms, and Equisetum. Most of the floricultural plants, vegetable and field crops, herbaceous plants, and many weeds are susceptible to attacks of this fungus. 3. The symptoms produced by RJiizoctonia Solani Kiihn in nat- ural infection are largely similar when appearing on the same type of host. The damping-off of seedlings and cuttings of various plants is identical, as is the rotting of a number of root crops. In most her- baceous plants a stem rot is produced, the symptoms of which are also identical on the various hosts. On very resistant plants lesions only are formed ; these are apparently the same on the different hosts. 4. From these inoculation experiments with a large number of different types of plants, we must conclude that all the strains studied, which were obtained from a wide range of hosts of diverse geographi- cal origin, can attack the same species of plant and produce the same characteristic symptoms. No marked specialization was noted in any of the strains. Thus all the strains studied can be included under one form, Rliizoctonia Solani Kiihn. The inoculation experiments show further that the virulence of R. Solani is very variable, as is also the degree of resistance of the various host plants, both depending on a number of varying factors. 1916} PARASITIC EHIZOCTOXIAS IN AMERICA 377 5. Studies of the growth of Rliizoctonia Solani Kiihn on media show that the strains are very variable, those from the same host often producing a different growth even on the same media, and that the differences in various cultural characters which are shown by strains from unlike hosts are no greater than the differences which may be manifested by two different strains isolated from the same host oi1 by the same strain at different ages. 6. Measurements of mycelial cells of RJiizoctonia Solani Kiihn shoAved such large variations, not only between strains from different hosts but also between different strains from the same host, that no standard could be determined on for distinguishing the different strains. 7. By means of a local soil survey, it was found that Rliizoctonia Solani Kiihn is abundant in cultivated land, where it may live either 011 dead organic matter in the soil or on weeds and other plants. 8. A certain vigor of mycelium must be attained before RJiizoc- tonia Solani Kiihn is able to attack a plant. A high temperature (88° F.), together with either too little or too much moisture, deter- mines to a large degree the virulence of the strains. It is only under certain conditions that the fungus becomes a dangerous parasite. The writer gratefully acknowledges his indebtedness to Dr. F. L. Stevens, Professor of Plant Pathology, and to Dr. J. T. Barrett, for- mer Chief Assistant in Botany, for their kind assistance and encour- agement. He wishes also to thank Professor H. B. Dorner, Assistant Chief in Floriculture ; Mr. C. C. Kces, formerly Assistant in Floricul- tural Pathology; and other members of the Division of Floriculture for assistance rendered during the progress of this work. 378 BULLETIN No. 189 [June, APPENDIX COMPOSITION OF MEDIA USED IN EXPERIMENTS Corn-Meal A gar (Shear*). — To 4 teaspoonfuls of corn meal add 1 liter of dis- tilled water. Keep in water bath for one hour at a temperature below 60 °C. Strain thru gauze, and to the filtrate add J percent agar flour. Steam three-quarters of an hour. Filter thru paper tube and place in autoclave for 15 minutes at 115° C. Green-Bean Agar. — 300 grams young string beans cooked in 500 ce wator for one hour and strained thru cloth. 15 grams agar (powdered) melted in 500 cc. water. Mix the two, add enough water to make 1000 cc., add 6 to 8 grams egg albumen, and boil in autoclave. Filter thru cotton. Oat Agar (Clinton*). — 200 grams oats ground fine thru a coffee mill and soaked in 500 cc. water for one hour. 15 grams agar melted in 500 cc. water and strained thru cheesecloth. Mix the two but do not filter, since the most nutrient part of the medium would be lost. Potato Agar. — 300 grams peeled potatoes, sliced as thin as possible and cooked in 500 cc. water for one hour. Strain thru cloth. 15 grams agar (powdered) melted in 500 cc. water. Mix the two and add enough water to make 3000 cc. Add 6 to 8 grams egg albumen (powdered) and boil in autoclave for a short time. Filter thru cotton. Potato-Glucose Agar. — 290 grams peeled potatoes, sliced as thin as possible and cooked in 500 cc. water for one hour. Strain thru cloth and add 20 grams of glucose. 15 grams agar (powdered) melted in 500 cc. water. Mix the two, add enough water to make 1000 cc., add 6 to 8 grams egg albumen (powdered), and boil in autoclave for short time. Filter thru cotton. Agar (CooTcc) Water 1000.00 cc. Agar 15.00 grams Glucose 20.00 Ammonium nitrate 1.00 Potassium nitrate 1.00 Ammonium sulfate 1.00 Magnesium sulfate .25 Dipotassium phosphate .25 Calcium chloridd 01 GROWTH ON MEDIA " ALFALFA" On Corn-Meal Agar. — Growth poor and rather slow. Mycelium white, fine, submerged, and scarcely visible. No coloring of the medium. No zonation. On Green-Hean Agar. — Growth poor and slow. Mycelium white, fine, loose, and becoming somewhat tufted. Zonation. Like strain from corn. On Potato Agar. — Growth rather slow. Characterized by the dark color of the mycelium and the turning of the medium to a darker color. Hypha3 loose, fine, and practically all submerged. No zonation. "U. S. Dept. Agr., Bur. Plant Indus., Bui. 252, 15. 1913. bConn. Sta. Rpt. (1909-10), 32, 760. 1911. cDel. Sta. Bui. 91, 12. 1911. dOmitted from formula used. 1916] PARASITIC BHIZOCTONIAS IN AMERICA 379 Stewart,125 in reporting the damping-off of alfalfa seedlings in the greenhouse and the crown rot of mature plants in the field, states that "the one causing dampincr-off of seedlings in the greenhouse is different from the one found in the field. When grown on potato agar (slightly acid, neutral, or slightly alkaline), the former produces a conspicuous dark brown discoloration of the medium, whereas the latter discolors it only slightly. This character may bo useful in the identi- fication of the damping-off Ehizoctonia. Such discoloration of the medium is not common among the species of Ehizoctonia." It is interesting to note that the strain obtained from Louisiana causing a damping-off of alfalfa seedlings and a number of other strains showed the same discoloration as the one studied by Stewart. On Agar XII. — Growth fair. Few loose, erect hyphae, becoming denser and finally forming an indistinct zone. " ALTERNANTHERA E. A. C." On Corn-Meal Agar. — Growth very rapid, but not dense. Mycelium white, loose, aerial, and fine. No zonation. On Green-Bean Agar. — Growth good. Mycelium tufted and compact, not turning darker. Zonation somewhat distinct at end of third day. Three zones present. On Oat Anor. — Growth rapid. Mycelium flat, and very compact, forming a mat over the surface. Zonation. On Potato Agar. — Growth very rapid, with zone formation beginning im- mediately. Mycelium all aerial and growing very compactly. Plate was covered at end of forty-eight hours and showed two distinct zones and one indistinct. On Potato-Glucose Agar. — Growth rapid; plate covered in forty-eight hours. Mycelium white, loose, and flaky. Zonation. On Agar X1J. — Growth good. Mycelium white, fine, compact, and somewhat flaky. Zonation. . "ALTERNANTHERA E. A. F." On the various media this strain produced the same kind of growth in each case as the strain from the cutting bench, except that it grew more rapidly. " ASTER" On Green-Bean Agar. — Growth fair. Mycelium white, loose, regular, joid flat, becoming somewhat tufted. Four zones formed at end of the fourth day. On Oat A gar. — Growth fair. Mycelium white, loose, flat, and regular, be- coming fluffy and tufted. Like strain "Carnation E. F." Five zones at end of fourth day. On Potato-Glucose Agar. — Growth slow and poor. Mycelium mostly submerged and turning brown. No zonation. On Agar XII. — Growth fair. Mycelium white, loose, flat, and regular, be- coming somewhat tufted. Zonation. "BEAN" On Corn-Meal Agar. — Growth very poor; scarcely visible. Mycelium white, fine, somewhat aeiiai. No zonation. On Green-Bean Agar. — Growth slow. Mycelium fine, aerial, loose, and white, darkening with age. Two zones formed, but not very distinct; otherwise like the strain from carrot. On Potato Agar.— Growth fair. Mycelium fine, more or less submerged, and discoloring the medium only slightly. No zonation. 380 BULLETIN "No. 189 [June, On Agar XII. — Growth rapid. Mycelium somewhat tufted and dense. Three distinct zones present. On Green-Bean Agar. — Growth good. Mycelium flat and compact. Several zones present. ' * BEGONIA ' ' On Corn-Meal Agar. — Growth fair. Mycelium rather compact and white. No zonation. On Green-Bean Agar. — Growth fair. Mycelium white, tufted, and compact. Zonation indistinct. On Potato Agar. — Growth fair. Mycelium compact, dense, and while; me- dium turning dark. Zonation. On Agar XII. — Growth scant. Mycelium white, fine, and loose. No zonation. ' ' CARNATION E. K. " On Corn-Meal Agar. — Growth good. Mycelium white, making a rather dense growth for corn-meal agar. Zonation indistinct. On Green-Bean Agar. — Growth good. Like strain "Carnation R. II." On Oat Agar — Growth good. Mycelium white, loose, edge tufted. Zonation. On Potaio Agar. — Growth poor. Mycelium loo^e and scattering, medium turn- ing darker. Zonation indistinct. On Agar XII. — Growth poor. Mycelium white, loose, and scattered; edge irregular. Zonation indistinct. " CARNATION R. H." On Corn-Meal Agar. — Growth fair. Mycelium white, fine, and in loose strands; rather dense at center. No zonation. On Green-Bean Agar. — Growth good. Mycelium dark at center, loose, and tufted; edge irregular. Zonation very characteristic of the strains isolated from diseased carnation plants. On Potato Agar. — Growth poor. Mycelium fine and scattered; edge irregular. Mycelium causing a characteristic browning of the medium. Zonation indistinct. On Agar XII. — Growth poor. Mycelium white, fine, loose, and scattered. No zonation. "CARNATION R. 8." On Corn-Meal Agar. — Growth fair. Mycelium white, fine, but rather dense at center; edge regular. Zonation. On Green-Bean Agar. — Growth good. Mycelium loose, white, and tufted; edge regular. Later, mycelium turned brown. Zonation somewhat indistinct. On Potato Agar. — Growth poor and scant. Mycelium producing a distinct browning of the agar. Zones indistinct. On Agar XII. — Growth poor. Mycelium white, scant, loose, and flat. Zonation. * ' CARNATION R. F. " On Corn-Meal Agar. — Growth good. Mycelium white, loose, and somewhat tufted. No zonatiou. On Green-Bean Agar. — Growth fair. Mycelium white, compact, and tufted. Zonation somewhat indistinct. 1916] PARASITIC EHIZOCTONIAS IN AMERICA 381 On Oat A (jar. — Growth good. Mycelium white, loose, flat, and fairly dense; edge tufted. Zonal ion. On Potato A gar. — Growth poor. Mycelium scant, like that produced by strains from carnation. On Potato-Glucose Agar. — Growth poor. Mycelium white, loose, scattered, and somewhat flaky ; edge very irregular. Zonation. On Agar XII. — Growth poor. Mycelium white, fine, loose, flat, and scatter- ing; edge very irregular. Zonation indistinct. ' ' CARNATION K.M.2 ' ' On Corn-Meal Agar. — Growth good. Mycelium white, tufted, and somewhat compact. No zonation. On Green-Bean Agar. — Growth fair. Mycelium white, tufted, azd compact. Zonation indistinct. On Oat Agar. — Growth fair. Mycelium white, loose, and somewhat flaky at center; edge loose and irregular. Zonation. OH Potato Agar. — Growth poor. Mycelium loose and fine. Zonation indis- tinct. On Potato-Glucose Agar. — Growth fair. Mycelium brown, loose, and flat; edge loose and tufted. No zonation. On Agar XII. — Growth fair. Mycelium white, loose, flat, and scattered. No zonation. "CARNATION K.D.C." On Corn-Meal Agar. — Growth good. Mycelium white, loose, tufted, and rather dense. No zonation. On Green-J lean Agar. — Growth good. Mycelium white, loose, tufted, and dense. Zonation distinct. On Oat Agar. — Growth fair. Mycelium white, somewhat dense at center, and more tufted at edge. Zonation. On Potato Agar. — Growth poor. Mycelium loose and flat, darkening slowly with age. Zoi.ntion indistinct. On Potato-Glucose Agar. — Growth fair. Mycelium white, flat, and flaky at center; edge loose and fluffy. Zones numerous and distinct. On Agar XII. — Growth poor. Mycelium white, somewhat flaky at center; edge irregular and scattered. Zonation. "CARROT" On Corn-Ideal Agar.— Growth good. Mycelium white, fine, and somewhat com- pact. No zonation. On Green-Bean Agar. — Growth poor. Mycelium loose, flat, and somewhat fluffy ; white at first, followed by purplish tinge. Zonation not very distinct. On Oat Agar.-r-Growth fair. Mycelium white, fine, loose, and flat. Zonation indistinct. On Potato Agar. — Growth fair. Mycelium dark, dense, and compact. Zona- tion indistinct. On Potato-Glucose Agar.— Growth fair. Mycelium dark, loose, flat, and flaky. Four to six zones present. On Agar XII.— Growth slow. Mycelium white, loose, and somewhat flaky. Zonation. 382 BULLETIN No. 189 [June, ( ' CAULIFLOWER ' ' On Corn- Meal Agar. — Growth poor. Mycelium white, loose, and scant. No zonation. On Green-Bean Agar. — Growth good. Mycelium white, tufted, and compact; edge regular. Zonation. On Oat Agar. — Growth good. Mycelium white, fine, loose, flat, and dense, running out in characteristic strands. No zonation. On Potato-Glucose Agar. — Growth fair. Mycelium dark, loose, flat, and flaky. One zone at outer edge. On Agar XII. — Growth good. Mycelium white, loose, flat, and flaky. Zonation. ' ' CHENOPODIUM ' ' On Green-Bean Agar. — Growth good. Mycelium white, flat, radial, and com- pact. No zonalion. "CLOVER (RED) " On Green-Bean Agar. — Growth good. Mycelium flat and compact. Zonation. "COLEUS I" On Corn-Meal A gar. — Growth good. Mycelium white, loose, and somewhat compact. No zonation. On Green-Bean Agar. — Growth good. Mycelium white, tufted, and compact. Zonation indistinct. On Oat Agar. — Growth good. Mycelium white, loose, and flat; edge fluffy. No zonation. On Potato Agar. — Growth fair. Mycelium loose and tufted, turning darker with age. No zonation. On Potato -Glucose Agar. — Growth fair. Mycelium dark, loose, and flaky; edge irregular. Zonation. On Agar XII. — Growth good. Mycelium loose, dense, and white. No zonation. "CORN" On Corn-Meal Agar. — Growth poor. Mycelium white, fine, and scattered. No zonation. On Green-Bean Agar. — Growth fair. Mycelium loose at edge and somewhat compact, turning darker with purplish tinge. Two distinct zones. On Potato Agar, — Growth fair. Mycelium dense and compact. Mycelium and medium turned dark. Zonation indistinct. On Agar XII. — Growth fair. Mycelium white, loose, tufted, and rather dense at center. Zonation. "COTTON I" On Green-Bean Agar. — Growth fair. Mycelium loose, tufted, dense, and white. Two zones present. On Oat Agar. — Growth good. Mycelium white, loose, flat, dense, and radial, later taking on a wrinkled appearance. No zonation. On Potato-Glucose Agar. — Growth fair. Mycelium white, flat, dense, flaky, and regular; loose at edge. Zonation indistinct. PARASITIC RHIZOCTONIAS IN AMERICA 383 On Agar XII.— Growth fair. Mycelium flat, somewhat dense, flaky and white at center ; edge loose. Two distinct zones. "COTTON II" On Green-Bean Agar. — Growth fair. Mycelium loose, tufted, and fairly dense later turning brown. Two zones present. On Oat Agar. — Growth fair. Mycelium white, fine, loose, and flat, forming a mat over surface of the medium. One zone present. On Potato-Glucose Agar.— Growth fair. Mycelium loose, flat, and fairly dense; edge irregular. Later both mycelium and medium turned brown. Two zones present. On Agar XII. — Growth fair. Mycelium white, loose, and somewhat tufted. Three zones present. "DlANTHUS BARBATUS N.P. ' ' On Green-Bean Agar. — Growth fair. Mycelium tufted and compact. Zonation indistinct. "DlANTHUS BARBATUS S.M. " On Green-Bean Agar. — Growth good. Mycelium tufted and compact. Zona- tion rather indistinct. "DlANTHUS PLUMARIUS" On Green-Bean Agar. — Growth good. Mycelium loose, white, and somewhat tufted ; edge regular. Zonation characteristic of the carnation strains. "DlANTHUS SEQUERl" On Green-Bean Agar. — Growth good. Mycelium loose, white, and somewnat fluffy; edge regular. Zonation characteristic of carnation strains in all respects. ' ' EGGPLANT I ' ' On Corn-Meal Agar. — Growth poor. Mycelium white, fine, and mostly sub- merged. No zonation. On Green-Bean Agar. — Growth good. Mycelium white, flat, radial, compact, and dense. One zone at center. On Oat Agar. — Growth fair. Mycelium white, loose, flat, interwoven, and somewhat tufted. Zonation. On Potato Agar. — Growth good. Mycelium dark, compact, dense, and radial. No zonation. On Potato-Glucose Agar. — Growth fair. Mycelium in radial strands, flat, and white. No zonation. On Agar XII.— Growth fair. Mycelium white, flat, dense, and compact. One zone present. ' ' GYPSOPHILA ' ' On Green-Bean Agar. — Growth fair. Mycelium white, fluffy, and somewhat compact. Zonation very characteristic of strains from carnation. ' ' LAVATERA ' ' On Green-Bean Agar.— Growth good. Mycelium white, loose, and tufted; edge even. Several zones present. 384 BULLETIN No. 189 [June, 1 ' LETTUCE » ' On Corn-Meal Agar. — Growth fair. Mycelium white, fine, slightly aerial, and somewhat flaky. No zonation. On Green-Bean Agar. — Growth good. Mycelium white, loose, flat, and rather dense, running out in strands. One indistinct zone present. On Oat Agar. — Growth fair. Mycelium white, loose, flat, interwoven, and somewhat tufted. One zone present. On Potato Agar. — Growth fair. Mycelium dark, fine, and practically all sub- merged. No zonation. On Potato-Glucose Agar. — Growth go»d. Mycelium white and flat, running out in radial strands. No zonation. On Agar XII. — Growth good. Mycelium white, loose, flat, and rather dense. No zonation. "ONION" On Green-Bean Agar. — Growth fair. Bright colored mycelium, fine and sub- merged at center; a little aerial mycelium at the outer edge, where it was some- what loose. No zonation. On Potato Agar. — Growth fair. Mycelium fine, scarcely visible, and of a bright color. No zonation. On Agar XII. — Growth fair. No aerial mycelium. No zonation. "POINSETTIA" On Corn-Meal Agar. — Growth fair. Mycelium white, dense, fluffy, and com- pact. Zonation indistinct. On Green-Bean Agar. — Growth fair. Mycelium white, loose, compact, and fluffy. No zonation. On Oat Agar. — Growth good. Mycelium white, loose, flat, and radial; edge somewhat fluffy. No zonation. On Potato Agar. — Growth fair. Mycelium somewhat flaky and compact. Three zones present. On Potato-Glucose Agar. — Growth fair. Mycelium brown and flat at center; outer edge white, loose, and somewhat flaky. Zonation indistinct. On Agar XII. — Growth fair. Mycelium white, flat, dense, and radial, like alternanthera. One zone. "POTATO E. SOL." On Corn-Meal Agar. — Growth fair. Mycelium fine and flat. No zonation. On Green-Bean Agar. — Growth fair. Mycelium loose at edge, compact and fluffy at center. Several zones present, two distinct. On Potato Agar. — Growth fair. Mycelium white and fluffy. One zone at center. On Agar XII. — Growth poor. Mycelium mostly submerged and somewhat com- pact; flaky at center. Zonation. "POTATO R.P.O." On Corn-Meal Agar. — Growth fair. Mycelium white, fine, and rather scant. No zonation. On Green-Bean Agar. — Growth good. Mycelium loose at edge, flat, dense, somewhat fluffy, and rather dark. Three zones present. Growth very much like strains from carnation. PARASITIC EHIZOCTONIAS IN AMERICA 385 On Potato Agar.— Growth fair. Mycelium dark, loose, and fluffy. Zonation distinct. On Potato-Glucose Agar.— Growth fair. Mycelium white, flat, loose at edge and flaky at center. Three zones present. On Agar XII.— Growth very slow. Mycelium white, dense, and bushy, form- ing a tuft at the center. No zonation. " SAL VIA " On Green-Bean Agar.— Growth good. Mycelium white, tufted, and compact Zonation indistinct. On Oat A gar.— Growth good. Mycelium white, loose, flat, rather dense, and radial. Zonation indistinct. On Potato-Glucose Agar.— Growth fair. Mycelium white and flaky at center; edge loose and tufted. Zonation indistinct. On Agar XII. — Growth good. Mycelium white and flaky at center; edge loose and tufted. Zonation indistinct. "SEDUM" On Green-Bean Agar. — Growth good. Mycelium flat and compact. One zone present. ' ' SUGAR CANE ' ' On Corn-Meal Agar. — Growth fair. Mycelium white, fine, and scarcely visi- ble. No zonation. On Green-Bean Agar. — Growth fair. Mycelium white, loose, and tufted. Zones present. On Potato Agar. — Growth fair. Mycelium white, fine, and practically all sub- merged. Two indistinct zones present. On Agar XII. — Growth fair. Mycelium white, fine, and running out in strands from the center. No zonation. ' * SWEET PEA ' > On Green-Bean Agar. — Growth good. Mycelium flat and compact. One zone present. In many respects like strain from carnation. ' < THISTLE ' ' On Corn-Meal Agar. — Growth fair. Mycelium white, running out in strands; flat at center, and somewhat loose at edge. No zonation. On Green-Bean Agar.— Growth good. Mycelium white, flat, radial, and com- pact at center; edge somewhat loose and fluffy. Zonation indistinct. On Oat Agar. — Growth good. Mycelium white, flat, dense, and radial. No zonation. On Potato Agar. — Growth fair. Mycelium white, flat, and somewhat compact, running out in strands. No zonation. On Potato-Glucose Agar. — Growth fair. Characterized by a white, radial, flat mycelium. No zonation. On Agar XII.— Growth fair. Mycelium white, flat, compact, and flaky at cen- ter, becoming looser at edge. No zonation. 386 BULLETIN No. 189 [June, BIBLIOGRAPHY 1. ANDERSON, H. W. Carnation Stem Rot Studies at Illinois. Florists' Rev., 29, 746, 26-27. 1912. 2. . Carnation Stem Rot. 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(Paris), 125, 730-732. 1897. 100. — — . La maladie de la gale de la pomme de terre et ses rapports avec le Bhisoctonia Solani Ktihn. Bui. Soc. Mycol. France, 13, 23-28. 1897. 101. SALMON, E. S. Diseases of Seakale. Gard. Chron., 103, 1, 3 figs. 1908. 102. SELBY, A. D. A Disease of Potato Stem in Ohio Due to Ehizoctonia. Science, n.s., 16, 138. 103. . A Eosette Disease of Potatoes. Ohio Sta. Bui. 139, 53-66, 5 figs. 1903. 104. . Studies in Potato Eosette II. Ohio Sta. Bui. 145, 15-28, 4 figs. 1903. 105. — — . Tobacco Diseases and Tobacco Breeding. Ohio Sta. Bui. 156, 97-99, pi. 1. 1904. 106. . Soil Treatment for the Forcing House. Ohio Sta. Circ. 57, 1-9, 2 figs. 1906. 107. . Soil Treatment of Tobacco-Plant Beds. Ohio Sta. Circ. 59, 1-3, fig. 1. 1906. 108. . A Brief Handbook of the Diseases of Cultivated Plants in Ohio. Ohio Sta. Bui. 214, 307-456. 1910. 109 SHAW, F. J. F. The Morphology and Parasitism of Ehizoctonia. Mem. Dept. Agr. 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Sta. Ept. (1908-1909), 32, 76-85, figs. 41-48. 1911. 120. STEVENS, F. L., AND WILSON, G. W. Ehizoctonia of Buckwheat. Jour. Elisha Mitchell Sci. Soc., 27-84. 1911. 121. — . Rhizoctonia of Buckwheat. Science, n.s., 33, 943. 1911. 122. . Clover Rhizoctonia. N. C. Sta. Rpt. (1910), 34, 70-73. 1911. 123. STEWART, F. C. The Stem Rot of Carnations. Science, n.s., 9, 172. 1899. 124. - — . The Stem Rot of Carnations. Bot. Gaz., 27, 129. 1899. 125. — . Notes on New York Plant Diseases I. N. Y. (Geneva) Sta. Bui. 328, 383-386. 1910. 126. , FRENCH, A. T., AND WILSON, J. K. Troubles of Alfalfa in New York. N. Y. (Geneva) Sta. Bui. 305, 392-393. 1908. 127. STIFT, A. Zur Geschichte des Wurzeltoters oder der Rotfaule (Ehizoctonia violacea). Osterr. Ungar. Zeitschr. Zucherindus. u. Landw., 42, 445-461. 1913. 128. STONE, G. E., AND SMITH, R. E. The Rotting of Greenhouse Lettuce. A Rhizoctonia Disease of Lettuce. Mass. (Hatch) Sta. Bui. 69, 16-17, figs. 9-10. 1900. 129. . Report of Botanist. Mass. Sta. 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WOLF, F. A. Fruit Rots of Eggplant. Phytopath., 4, 38. 1914. 141. - — . Eggplant Rots. Mycol. Centbl., 4, 278-287, figs. 3-4, 1914. 142. WOLLENWEBER, H. W. Pilzparasitare Welkekrankheiten der Culturpflanzen. Ber. Deut. Bot. Gesell., 31, 30. 1913. NOVEMBER, 1915 BULLETIN University of Vermont and State Agricultural College Vermont Agricultural Experiment Station BURLINGTON, VERMONT THE RED ROT OF CONIFERS by F. H. ABBOTT (Vermont forestry publication 19) BURLINGTON : FREE PRESS PRINTING Co. 1915. BOARD OF CONTROL PEES. G. P. BENTON, ex-officio, Burlington. HON. E. J. ORMSBEE, Brandon. HON. N. K. CHAFFEE, Rutland. OFFICERS OF THE STATION • J. L. HILLS, Director. F. A. RICH, Veterinarian. C. H. JONES, Chemist. A. F. HA WES, (State Forester), Forester. M. B. CUMMINGS, Horticulturist. B. F. LUTMAN, Plant Pathologist. G. P. BURNS, Botanist. G. F. E. STORY, Animal and Dairy Husbandman. A. K. PEITERSEN, Assistant Botanist. JENNIE L. ROWELL, Assistant Chemist. C. G. WILLIAMSON, Assistant Chemist. G. F. ANDERSON, Assistant Chemist. W. C. STONE, Assistant Horticulturist. H. E. BARTRAM, Assistant Plant Pathologist. R. C. DOWNING, Assistant Veterinarian. E. R. BAKER, Computer. W. H. CROCKETT, Editor. S. HARGREAVES, Gardener. M. ADELLE ORTON, Stenographer. ETHEL BINGHAM, Stenographer. MAY O. BOYNTON, Librarian. C. P. SMITH, Treasurer. ts" Copies of the reports and bulletins of the Station are sent free of charge to any address upon application. SS" Address all communications concerning station matters not to in- dividual officers, but to the Experiment Station, Burlington, Vt, address inquiries concerning farm practice to Extension Service, Burlington, Vt. Director's and State Forester's offices, chemical, horticultural and dairy laboratories are in Morrill Hall at the head of Main street; botanical and bacteriological laboratories are at Williams Science Hall, University Place; veterinary laboratories are at 499 Main street. University farm and buildings are on the Williston road, adjoining the University grounds on the east. PLATE I. Cross section of eight-inch pine showing permeation of sap-wood by the fungus (upper). Cross section of diseased pine (lower). PLATE II. Longitudinal section of pine showing appearance of infected wood (main view). Fruiting body of Trametes Pini on a fourteen-inch pine, together with pitch exudate below fruiting body (in upper right hand corner). BULLETIN 191: THE RED ROT OF CONIFERS BY F, H. ABBOTT! SUMMARY The so called red rot of conifers is caused by the fungus Trametes Pini, which is primarily a parasite, assuming more or less the characters of a saprophyte when the tree falls. The fungus commonly attacks five species of conifers: tamarack, pine, hemlock, spruce and balsam. Its ravages are greatest in unthinned stands, especially pure stands of white pine. Infection occurs mainly through broken branches which ex- pose the heart-wood. Root infection is doubtful. Sporophores are the principal means of spreading the disease. They form on all host species but vary in form from an incrustation on the spruce and balsam to a bracket or hoof on pine and tamarack. They exist on both standing and falling trees. The mycelium spreads more rapidly up and down the trunk than across it. The damage to the wood is wrought by the solution of its lignin content by the enzym of the fungus. This damage appears to cease when the tree falls. Laboratory cultures of the fungus from various sources ex- hibited uniformity. Spores were not produced in the cultures, at least up to six months. Successful cultures may be made on sterile wood. Prevention is best effected by proper thinnings, removing dis- eased trees and destroying fruiting bodies. The weight, breaking and crushing strengths of the woods were decreased approximately in proportion to the permeation of the wood by the fungus. The red rot of conifers damages Vermont timber owners an- nually to the extent of about a quarter of a million dollars. The diseased wood is used in the manufacture of boxes, tubs, wooden pails, etc. 1 The writer expresses his appreciation of the assistance he has received from Arthur S. Graves of Yale University, B. A. Chandler of the Vermont Forestry De- partment and from the Station Forester and Plant Pathologist in assembling the data and in preparing this paper. The collection of references was facilitated through the assistance of Perley Spaulding of the United States Department of Agriculture. Valuable specimens were contributed and field observations made by Mr. Chandler. The collection of the data regarding losses in the mills and woods was accomplished only through the cordial cooperation of landowners, millowners and operators. C. G. Hedgecock of the United States Department of Agriculture also assisted in the identification of sporophores and diseased wood. 4 BULLETIN 191 I. FINANCIAL LOSSES •^ According to the 1910 census report, reviewed by the United States Forest , Service in Vermont Forestry Publication No. 11, "Wood Using Industries of Vermont," Vermont produces lumber, lath and shingles from pine, spruce, hemlock, tamarack and fir, totaling 194,273,000 board feet. Were this all sound timber, free from red rot and other defects, it would average at the mill $20 per thousand square edged. As a result of the writer's inspection of lumber in twenty mills and yards in various parts of Vermont in the spring of 1913, it is estimated that on account of the red rot nine percent of this total is reduced to a grade worth approximately $10 per thousand. In other words, on a total of 17,484,570 board feet of timber affected by red rot, there is an annual loss of $174,845. But this is not all. These figures are taken at the mills and ship- ping points and do not represent the lumber before it is marketed. Much of the timber — calculated, from observation in the woods and estimates by lumbermen, at 2 percent of the actual cut in the woods — is so badly diseased with red rot as to be entirely useless. This, of course, never is hauled from the stump. Basing the calculation on the census figures and for the total output, this absolute loss of 2 percent totals 3,885,460 board feet. Sound logs to this amount would be worth in the woods approximately $25,000. In addition to these losses there is the great loss to trees which become diseased and are dying constantly in the forests, eventually falling to the ground and rotting. The total annual loss to Vermont timber owners due to the red rot disease, therefore, may be placed approximately at a quarter of a mil- lion dollars. The percentages used in this calculation were averages taken from data collected in person by the writer from actual mill tallies, observa- tions and quarter-acre circle tallies made in the woods, and from figures and estimates furnished by mill owners and operators throughout northern Vermont. Investigations made by the writer indicate that in white pine lots there was a loss of 8 percent of value due to the disease; in pure spruce 3.5 percent; and in mixed conifers, 5 percent. II. EXTERNAL EVIDENCES To the lumberman or wood-chopper the evidence of the presence of red rot in a standing tree in the forest is unmistakable. If a glance THE RED ROT OF CONIFERS 5 at its general appearance does not tell him, he sounds the tree with his axe to see if it is worth felling. To the untrained person, however, considerable observation is necessary to judge with any degree of ac- curacy whether a tree is or is not diseased. Of course the discovery of a fruiting body (Plate III) is a sure indication, but aside from this evidence one can judge only from general appearance. Perhaps the most reliable indication, at least in the pine and spruce, is the abnormal exudation of pitch or resin from old knot-holes, or, if the disease has progressed far enough, from other points on the bark. This pitch drops down the sides of the tree and is very noticeable, as is shown in Plate II, upper left hand corner. If the fungus has invaded the trunk of the tree sufficiently to affect its health seriously, a general paleness of the bark and even of the foliage ensues. These evidences are not confined to any particular part of the trunk. The very first stages of the disease are betrayed by this pitch exudate. Suspected trees manifesting these early evidences of the malady were cut, which, upon internal examination, revealed only the red color of the heart- wood, which is the result of the first structural change brought about by the fungus. Later in the progress of the disease all the external evidences become intensified so that advanced stages are detected more easily. III. SPECIES AND CONDITION OF TYPES ATTACKED Susceptibility of species. Red rot is found commonly in the five soft wood species: pine, spruce, hemlock, balsam and tamarack. Von Schrenk (2) states that "of the five trees the tamarack seems to be the most readily attacked, the spruces come next and the balsam fir last." Although tamarack is not as plentiful in Vermont as the other species, the writer's observations tend to confirm Von Schrenk's statement as to its susceptibility. In regard to other species, however, the writer's study of his data leads him to conclude that, in Vermont at least, white pine is second in susceptibility, while spruce, hemlock and balsam arex susceptible to invasion in about the same degree. It was noted that spruce in mixed stands appeared more prone to attack than when grow- ing in a pure spruce stand. This is not easy to explain, unless it may be due possibly to better self-pruning and to more healthy and favor- able silvicultural conditions. Pure white pine stands showed greater amounts of red rot than did any other type. Where the disease was present at all in the white 6 BULLETIN 191 pine, it seemed to be distributed much more uniformly than in the mixed stands. Silvicultural conditions. Certain silvicultural conditions appeared to favor the" presence and spread of the disease. It was predominant especially in tracts which were in need of thinning. A notable case of this sort was found in Orange County where the trees ranged from 6 to 14 inches in diameter at breast height and were growing so close- ly together that the wind had broken many branches. The heavy mass of crowns did not allow the entrance of sunlight, which is an important factor in the healthy growth of a forest. Topography. So far as could be determined, the effect of topog- raphy upon the presence of the fungus seems very slight. The reports of lumbermen on this point were variable and evidently were governed by local conditions. Comparison of the opinions of lumbermen in dif- ferent localities, strengthened by the writer's observations in the woods, leads to the conclusion that red rot lumber is as common on high rocky land as in the swamps and lowlands, with the exception of tamarack which, of course, occurs only in lowlands. Wind. It is believed that the wind is a more important factor than topography. Areas exposed to heavy winds show more red rot decay than do sheltered stands. This condition might be explained by the fact that the damage done by the wind in breaking branches leaves open places or branch wounds where the fungus may enter the tree. The wind also aids in carrying spores from one tree to another. Age. Previous writers have ascribed much importance to the supposed fact that only the oldest trees in the stand are affected. While this may be true in some sections, many specimens of trees not more than 25 or 30 years old were found by the writer to be infected. Von Schrenk's statement that the fungus attacks living trees only after they have reached the age at which they form heart-wood, probably is a more correct conception of the matter. IV. DISTRIBUTION Numerous German references report the occurrence of this fungus in all parts of that country where any considerable stands of coniferous trees are found. Moller (5) says "It is present wherever the conifers grow in any abundance and the damage caused by it reaches into the millions of dollars annually." Hartig (1) states that it is very abun- dant in the pine woods of North Germany and occurs also, but less THE RED ROT OF CONIFERS 7 frequently, in the spruce woods of South Germany. That it affects the conifers in other eastern countries is evidenced by the report of Khan (6) on its occurrence in India in 1904. Von Schrenk (2) has reported in a general way on its occurrence in Maine and other New England states on white pine, red spruce, white spruce, hemlock and tamarack. The parasite attacks living trees after they have reached the age at which they form heart- wood, and honeycombs the wood in such a way that it appears to be filled with small holes, many of which seem to have a slimy white lining. The writer has tried to secure information which would afford accurate data concerning its occurrence in Vermont, by the collection of statistics from different parts of the State. The percentages of dis- ease in spruce and mixed stands appear to be fairly uniform in all places where data were obtained. With the exception of a few local situations, either badly infected or entirely free from disease, one may expect to find in most cuttings losses varying from 3 to 5 percent. The presence of the disease, however, was not as uniform in pine trees as in the others mentioned. Many small tracts, especially isolated ones, were found where no disease was apparent. On the other hand other places were found where many trees were affected and the loss was very large. With the exception of the Passumpsic valley, which appears to be excellent pine land, and where very little red rot was found, the dis- tribution of the disease is irregular. Along the shore of Lake Cham- plain, tracts less than ten miles apart were located where both ex- tremes of conditions were found. The Connecticut valley shows a sim- ilar condition. It is the writer's opinion that the best pine lands show the greatest freedom from disease because the more rapid and uniform growth results in better self-pruning and healthier general conditions. V. THE FUNGUS Name. The fungus causing the red rot of conifers is one of the Basidiomycetes, Trametes Pini. It is a parasite of growing coniferous trees and assumes the characters of a saprophyte, (that is to say, a fungus living upon a dead plant or animal) to a greater or less extent upon the death of the tree, so long as the moisture and food contents of the host remain favorable to its development. The question of its adaptability to a saprophytic mode of life is one of much economic im- 8 BULLETIN 191 portance from the point of view of its ability to continue the forma- tion of fruiting bodies on fallen trees and thus greatly to increase the spread of the disease. Growth of mycelium. Von Schrenk (2) states that destruction of the wood, at least, ceases upon the fall of the tree, but that whether the fruiting bodies on fallen trees do or do not function to any great extent remains an open question. That the growth of the mycelium (the thread-like tubes which penetrate the wood and nourish the fun- gus, tubes which in their function are analogous in a way to the roots of higher plants) in fallen trees is dependent almost entirely upon moisture conditions, was proved conclusively by the writer by taking uniform slabs of diseased pine, placing them in various conditions of moisture and- watching the progress of the growth of the mycelium and the destruction of the wood. Slabs placed under cover where con- ditions are such as are found ordinarily where lumber is seasoned, showed no further growth of the fungus. The wood dried out and its pithy appearance assumed a more open character. On the other hand, slabs of the diseased wood left in contact with the ground, or near moisture, showed abundant growth of the mycelium, which ex- tended even to the surface of the wood. Whether infected wood left in such conditions ultimately would or would not form functioning fruiting bodies, is undetermined. However, it is believed that trees which fall in the woods as a result of permeation by the fungus do not fall ordinarily under such conditions as tend to favor the con- tinued growth of the mycelium. The trunk of the tree is more likely to be attacked by fungi such as Lenzites sepiaria and other saprophytes that can live in a drier situation. Method of attack. Any tree wound which opens up a way to ex- posed heart-wood enables the red rot fungus to germinate and the mycelium to penetrate the wood. Once the mycelia have gained en- trance, they spread rapidly, both up and down the trunk, along the tracheids (i. e. wood cells used simply as water carriers) longitudinally, and more slowly across radially. Resistance. Apparently the only resistance offered by the tree takes the form of a free exudation of pitch. In the younger trees this discharge is sufficiently large to hinder the progress of the mycelium while the lessened amount of pitch which is exuded by the older trees accounts for the increased destruction. It is stated by Von Schrenk (2) that the mycelium of Trametes Pini flourishes in both the heart-wood and sap-wood of spruce, hem- THE RED ROT OF CONIFERS 9 lock, fir and larch, while in pine it grows only in the heart-wood. That the latter is not always true is shown in Plate I of a cross section of an eight-inch pine, in which it will be noticed that the destruction has continued irregularly into the sap-wood. This specimen was taken from a standing tree upon which a fruiting body was found. Figure 1. Part of stem of a pine bearing sporophore of Trametis Pini (one half natural size) (After Hartig). Hartig (1) says the fungus cannot enter through old branches naturally pruned. This point was investigated and it was found that the tree forms a natural protection for itself. When the branch dies the free exudation of pitch causes that part which lies adjacent to the cambium, (the growing tissue just inside the bark), as well as that inside the tree to become hardened and impenetrable. This con- 10 BULLETIN 191 dition is, shown clearly in Figure 1, which is a longitudinal section of a diseased pine, cut squarely through the center of the knot. It will be noticed that the fungous growth is present in the vicinity but does not penetrate this resinous wood of the old branch. Morphological characters; wood dissolution. The visible effects of the growth of the fungus in the wood are described by Von Schrenk (2) for spruce in part as follows: "The first effect to be noticed is a change in the color of the. wood from natural light straw color to a purplish gray. Very sflon this gray deepens to a red brown. Black lines precede the appearance of small white areas. These areas usually are some distance from each other and are arranged longi- tudinally (Plate II). Some of the holes fill with a mass of white fibers. As the holes grow in number and size they appear to unite longitudinal- ly rather than radially. As the disease advances in the tree, the destroyed cells fill with a dark brown mass of hyphae1. These hyphal plugs occur in nearly every tracheid and are accompanied by a brown incrustation which dissolves in part in dilute potassium hydroxid and entirely in warm nitric acid. These incrusting substances apparently were decomposition products and were laid down in liquid form. "The changes in the cell walls resulting from the attack of the mycelium are fully described by Hartig (1). There is a gradual ex- traction of those elements which give a lignin2 reaction due to the probable secretion by the fungus of lignin-dissolving enzyms.3 This be- gins in the tertiary lamella and proceeds outward slowly through the secondary lamellae. The primary lamella splits at this state and dis- solves, leaving the individual tracheids entirely free from each other and composed approximately of pure cellulose. The white spots are the points at which the change to cellulose has taken place. Preceding the change of the wood fiber to cellulose, the wood is filled with masses of hyphae which become masses in centers and bring about the dis- solution of the wood. "The hyphae grow out from the original centers in all directions, proceeding faster up or down the stem parallel to the tracheids than they do across them. It is the opinion of the writer that the decom- position products cause the destruction of the wood to stop at this point. In the newly invaded trunks the mycelium is colorless. The hyphae are somewhat thick walled and have numerous short branches which penetrate the walls in all directions." 1 The term "hyphae" as used here, is synonymous with mycelia. 2 The woody substance of the cell wall. 3 An enzym is a ferment possessing the power to decompose organic compounds. THE RED ROT OF CONIFERS 11 Figure 2, copied from Hartig, shows more clearly than can be explained the appear- ance of the mycelium in the tracheids and the gradual solution of the lignin brought about by the enzym of the fungus. VI. CULTURAL STUDIES Specimens of diseased wood were secured from several sections of the State, though mostly from forests near Burlington, in August, 1912, the trees being in various stages of decay. These specimens were examined microscopically and the fungus was grown on lima bean agar (Clinton's formula) and a syn- thetic agar composed of peptone and the neces- sary salts, which was strongly acid in its re- action. Inoculation methods. Some samples for inoculation were taken from standing trees on which fruiting bodies had developed, others from logs or sawed lumber in lumber yards, Figure 2. A tracheid an^ in two cases successful cultures were made of Pinis sylvestris which f rom particles of wood taken from a knot-hole has been decomposed by Trametes Pini. The pri- in a suspected pine upon which no fruiting body could be found. The mycelia obtained from all these sources showed noticeable uni- formity in their growth or media. Particles of fruiting bodies also were used for inocula- tions and, in comparison with each other and the cultures made directly from wood, gave equally uniform results. Most of the inoculations were made directly from the specimens of wood. By carefully handling the specimens with sterile forceps and cutting away the external portions of the wood with a sterile knife, small particles of the diseased wood fiber were obtained, which, when introduced upon the surface of the tubed media, gave about 90 percent of pure cultures. Mycelial growth. At first the mycelium made slow growth, from mary cell-wall has been completely dissolved as far as aa. In the lower portion of the figure the secondary and tertiary walls consist of cellulose alone, in which granules of lime are distinctly recognizable, b; fila- ments penetrate the walls and leave holes behind, d. e. (After Hartig). 12 BULLETIN 191 ten days to two weeks being required before visible growth could be detected in the tubes. Plate IV shows a photograph of a six-weeks- old culture on lima bean agar. During the first stages of the growth the hyphae, (that is to say, the filaments of the fungus), were pure white in color. They spread over the entire upper surface of the media, forming a mat about one-sixteenth of an inch in thickness. In no case did they penetrate the media to any extent. Inoculations were made upon media in deep petri-dishes, about 2.5 inches deep and 3.5 inches in diameter, in order to promote a longer period of mycelial growth before the media began to dry. The growth in the petri-dishes was not essentially different from that in the tubes. In all cases the mycelium retained its white color for a period of from six to eight weeks, then slowly turned to a brown which grew steadily darker for about eight weeks, after which time there seemed to be little increase in amount of mycelium and no change in color. The brown color exhibited so uniformly by the culture apparently is due to a sort of incrustation which is laid down about the mass of mycelium. The fact that this incrustation is soluble in part in potassium hydroxid and entirely in warm nitric acid indicates, as Von Schrenk (2) has stated, that it is due to the presence of decomposition products. This coloring matter diffused through and stained brown the lima bean agar after two months. The growths on the two kinds of media differed only in minor particulars. Sterile wood cultures. In order more closely to follow the fungus in its attack upon wood, cultures were made in the following manner : Small blocks were sawed from each of seven different kinds of healthy wood, spruce, pine, hemlock, tamarack, balsam, birch and oak. These blocks were taken from the trunks or branches and sawed in such a manner that both heart-wood and sap-wood were present in each block. They then were put into an ordinary test tube, in the bottom of which had been placed previously a small ball of water-soaked cotton. The tubes then were plugged and sterilized. Inoculation was accomplished by introducing small particles of mycelium from previous media cul- tures. Growth in the dark and at room temperature started on the wood almost immediately and spread irregularly over the entire sur- face of the block. Eight inoculations, besides a check, were made on each kind of wood and in 95 percent of the tubes the cultures ap- peared pure. The fungus apparently showed no preference for the sap-wood. Growth on different species. Comparison of the amount of hyphae THE RED ROT OF CONIFERS * 13 in the tubes showed that the susceptibility of the wood seemed to range in order as follows : Tamarack, pine, hemlock, spruce, balsam. This order of susceptibility is the same practically as that noted by Von Schrenk (2) in New England forests. The inoculations made on oak and birch were successful, the fun- gus growing luxuriously ; but the damage to the wood was done more slowly and its extent relatively was very limited. The attack of the fungus on the hard woods should be studied more thoroughly. The preliminary sterilization, of course, may have rendered them soft and also may have brought about chemical changes which rendered them more readily open to attack than when in their natural state. The brown incrustation occurred fully four weeks later in the case of all eight cultures of the tamarack and balsam than in the cultures on pine, spruce, and hemlock inoculated at the same time. Microscopical examination revealed no essential difference in the fun- gus as cultivated on the different woods, except that the hyphae cells possibly were a little larger in diameter on the tamarack and smaller on the hard woods. Influence of moisture. The growth of the fungus is profoundly affected by the presence or absence of water in the tubes. Without exception whenever moisture was lacking to any great extent, the growth of the fungus was affected directly. If water was omitted at the time of inoculation, the culture failed to develop. If the fungus grew luxuriantly in the presence of moisture it ceased its growth im- mediately and dried up if the water supply was withdrawn. Tubes in which this drying out process had taken place once, but slowly re- established growth upon the addition of water. Spores. The cultures were examined microscopically at various stages for spores. The last of these examinations was made in May, 1913, and, even on cultures which had been growing since September, 1912, no trace of such reproduction could be found. The marked uni- formity of the general characters of the mycelium, noticed in all the slides prepared from the different cultures, indicated that the same fungus had been isolated in all cases. The growth of the fungus on the sterilized wood cultures produced the same appearance as that taken from a diseased tree in the forest. Blocks of wood are shown in Plate IV on which the fungus had flourished for a period of six months but from which the mycelium was scraped from the wood to show more clearly the presence of the white-lined pockets which are so characteristic of the disease. JL4 BULLETIN 191 ' VII. EFFECT OF THE FUNGUS ON THE WOOD The change from the natural color of the wood to a red brown has been responsible for the name of "red rot" lumber, by which woods- men and lumbermen designate the diseased wood. Breaking and crushing strength tests. In order to show the ex- tent to which the changes wrought by the fungus as outlined on pages 7 to 10 take place, and to afford a comparison of diseased and healthy wood from the standpoint of the Tise of lumber for manufacturing pur- poses, tests of breaking and crushing strengths were carried out as follows : A complete section of a diseased pine log about 12 inches long was taken from a standing tree in Bradford. This tree was about eight inches in diameter and about 35 feet high. A fruiting body was found at a knot-hole four and one-half feet from the ground. A cross sectional photograph (Plate I) indicates the extent to which the fungus had penetrated the wood. This 12-inch section was seasoned in a boiler-room where it was subjected approximately to the heat em- ployed in an ordinary kiln-drying process. The log then was sawed as economically as possible into sticks with an average measurement of 1.1 x 1.2 x 10 inches. These sticks were assorted then into three classes, according to the extent to which the fungus was present in each, as follows: (1) Showing very little or no evidence of disease. (2) Fungus growth on one or two sides. (3) Thoroughly ramified by the fungus. The weight of each stick and its volume by displacement of water were obtained. Breaking strengths were determined on sticks ten inches long and crushing strengths were determined on five-inch lengths.1 Four sets of tests were conducted for each class. A summation of re- sults follows: SUMMARY OF TESTS FOR THE THREE CLASSES Class Volume Weight Diameter Pounds Pounds c.c. grams inches to break to crush Free from disease 240 89 1.1 x 1.2 x 10 610 6620 Partial infestation 247 78 1.1 x 1.2 x 10 498 3910 Complete infestation 248 67 1.1 x 1.2 x 10 337 2440 This table is self explanatory. It shows plainly the relative de- .crease in weight and in breaking and crushing strengths proportional to the extent to which the fungus had penetrated. 1 The strength tests were carried out in the College of Engineering under the direction of J. O. Draffin of the Class of 1913. THE RED ROT OF CONIFERS 15 Clearly the fungus is capable of destroying the wood and makes it unfit for manufacturing purposes. The advisability of cutting and marketing trees affected by the disease as soon as the presence of the fungus is noted, is evident. In this way only can the timber be used at all. It should be noted that the strength of the sticks cut from dis- ease-free wood corresponds closely to that of standard seasoned pine. This tree, as a whole, however, was affected so seriously with disease that at least 50 percent of it would have fallen into a $10 grade, and 25 percent of it was utterly useless. VIII. METHOD BY WHICH THE FUNGUS SPREADS THROUGH A FOREST Root infection. According to Khan (6) an examination of vari- ous specimens of the roots of coniferous trees in an East Indian for- est infected with Trametes Pini showed that there is a strong possibility that the disease may spread by the passing of the mycelium from the roots of diseased to those of healthy trees. Even more striking is Runnebaum's (4) statement based on the inspection of 70 infected trees, to the effect that 50 of them had been infected from the roots. A careful examination of the roots and trunks of these 50 trees, on the side on which the fruiting bodies occurred, showed mycelium up to a point only half a meter higher than the level of the ground. The infection in the other 20 trees evidently had occurred in a branch wound, because the rot was confined to the parts above ground. While this channel of infection may be open to some cases, the chances of the fungus penetrating the cambium and sap-wood of an uninjured root seem rather slight. In any case the fungus can be spread thus but slowly. The writer is of the opinion that root infection does not take place to any great extent in this locality, certainly very few of the specimens seen in Vermont were diseased below the ground. It may be that the fungus has been confused with its closely allied form, Trametes radiciperda, which produces much the same condition of de- cay in the wood but is spread solely by underground methods, its fruit- ing bodies forming below the surface. Tubeuf (3) has made clear the distinction between Trametes Pini and Trametes radiciperda, although the two species produce much the same condition in the wood. Fruiting bodies or sporophores. The fungus follows in general the habits of other wood fungi and spreads through a forest mainly by the production of spores in a fruiting body, or sporophore. That these sporophores are very plentiful on the diseased trees in German forests 16 BULLETIN 191 is indicated by the constant reference made to their occurrence by German writers. Von Schrenk (2) speaks of them as being "extreme- ly common on all (New England) affected trees." Specimens have been collected from forests in Maine, New Hampshire, Vermont, New York, Ontario, Quebec and New Brunswick. However, the writer did not find these fruiting bodies as common, at least in Vermont, as they have been represented to be. No trace could be found on a large proportion of the infected trees, the only external sign of the dis- ease being an abnormal exudation of pitch from knot-holes and a gen- eral pale and unhealthy condition of the foliage. However, the sporo- phores were found occasionally on every diseased tract. The sporophore of Trametes Pini is easily distinguished from al- lied forms by the light red-brown color of the hymenial or fruit-bear- ing surface and by the regular small round pores. The pores on the specimens obtained in Vermont seem smaller than those occurring on specimens from other sections. The form of the pileus or cap varies with the species of the host plant. Hartig (1) ascribes this difference to the various amounts of resin contained in the trees of the several species. The sporophore on the pine appears characteristically in the form of a large bracket, situated on the surface of the tree where an old branch stub has broken off. Plate III shows this characteristic ap- pearance. An exudation of pitch almost always accompanies the pres- ence of the fruiting body. Plate III shows two specimens of fruiting bodies or sporophores collected, respectively, at Bradford and Bur- lington. In the case of the spruce, tamarack and fir, these characters do not hold. The form of the sporophore varies from that of an in- crustation to that of a bracket, and it does not confine its location to the nodes but may develop at any point. These sporophores give rise to the spores which are carried about by the wind until they find a suitable place for germination. Where old branches have been broken off, exposing the heart-wood before com- plete protection to the wound has been effected "by the resinous deposit in the branch stub, the spore finds the most favorable conditions for entrance and germination. Its progress in the heart-wood is rapid, but when it reaches the resinous sap-wood its advance is slower. About this time the sporophores begin to form. Where the dead branches have been broken off close to the trunk, the hyphae grow out from the stub and form a cushion. Von Schrenk (2) has explained carefully in de- tail the progress of the growth of the sporophore on pine, spruce and tamarack. The cushion formed on the branch stub is very small at THE RED ROT OF CONIFERS 17 first and has the appearance of being covered with velvet. The radial growth of the hyphae is rapid and a sheet is formed which adjusts itself to the shape of the stub. At the edges this sheet projects from the bark and forms an irregular shelf, the top of which after a time becomes brown and hairy and ultimately develops into a bracket for- mation. The growth seems to take place most rapidly through the latter part of the summer and the early fall. The hyphae at the edge of the sheet extend their area, while those forming the walls of the pores grow vertically downward. It is not known to what age one of these sporophores may attain. Most writers call attention to the fact that fruiting bodies are common only on the larger and older trees. While this is true to a cer- tain degree, the production of sporophores by no means is confined to such trees. The writer found that they were as common on diseased trees less than seven inches in diameter as they were on larger and older trees. One good specimen was found on a pine about six inches in dia- meter and only about 30 years old. The entire surrounding stand in this case was only from 45 to 50 years old and fully as large a percentage of diseased trees was detected here as in any stand examined. These fruiting organs exist on both standing and fallen trees. Von Schrenk says : "They were found on trees which had been cut down four years before and new ones were constantly appearing." In view of the fact that the mycelium practically ceases growth as soon as the wood is placed in a position where desiccation will take place, it would seem that such sporophores could not be kept in a condition to function for any length of time after the fall of the tree, unless the tree fell in a position to cause the excessive absorption of moisture. However, it is this faculty of -fruiting to a greater or less extent on dead trees which must enable this fungus to accomplish its rapid spread. IX. PREVENTIVE MEASURES The discovery of this disease and of its method of spread in Ger- many immediately led to search for some means by which its ravages could be controlled. Most students of this malady as it occurs in Europe have suggested the following procedure: 1. Prevention of branch breaking. Laws have been enacted to prevent wood gatherers from breaking off branches which leave an open wound in the heart-wood, thus encouraging the entrance of the fungus. These wood gatherers damage forests which lie near cities and villages. They are supposed to take only the dry dead branches, 18 BULLETIN 191 but in -so doing often remove branches which still are partly green and in which the protective layer of resinous wood has not formed. 2. Removal of fruiting bodies. If fruiting bodies are removed and destroyed and a disinfectant is applied to their former sites on the trees much good will be accomplished. This may be done according to Moller (5) by a crew of two or three men equipped with ladders with instruments for hewing out the sporophores and with some form of disinfectant to apply to the spots where the fruiting bodies were located. Caterpillar tar (Raupenleim) is the disinfectant com- monly used in this work. Its application in this manner is known to have prevented the formation of new fruiting bodies in at least 80 percent of the cases where it was used. Kienitz (8) states that it costs about 10 cents an acre to do this work. 3. The cleaning out of infected trees. Infected trees can be recovered thoroughly only by a careful survey of the tracts by a man who is trained in detecting the disease. The complete removal of the whole tree is necessary because of the chances of further infection, either from the mycelium or from fruiting bodies on the fallen trees. This operation should not be expensive, as enough of the lumber cut would be worth saving to pay for the cutting. This cutting could be made best in the form of a thinning. Hollrung (7) advises a complete inspection and cleaning of an infected forest every five years in order to maintain complete control of the disease. Obviously all these methods are radical and are applicable in their entirety only where intensive forestry can be practiced. The problem of prevention in this country assumes a different aspect because lumber prices do not permit as intensive methods as obtain in Europe and because the sporophores apparently do not grow as abundantly, in the Northern states at least, as they do in Germany. In view of the fact that evidence points toward the probability that fruiting bodies may form and function on dead trees, it appears that the first procedure should be to remove carefully all dead and dis- eased wood so that it will not spread the disease. Then, secondly, over- thick plantations should be thinned. The writer noted a significant fact in his study of Vermont forest conditions in their relation to red rot, namely, that the disease was much more prevalent in stands in need of thinning and of an improve- ment of silvicultural conditions than in well-handled stands. Proper thinnings should be made, if possible, in rotation. Thinnings thus PLATE III. Sporophore of Trametes Pini on pine; very nearly actual size PLATE IV. Wood chips upon which Trametes Pini had flourished for six months. Mycelium is scraped from outside to give clearer view. From left to right: check, pine, tamarack, hemlock, spruce, balsam (upper). Butter tub cover; showing how infected wood is utilized (middle). Trametes Pini growing in cultures (lower). THE RED ROT OF CONIFERS 19 periodically made at intervals not more than 20 years apart, should pro- vide easily for the removal of all diseased trees. In the University forest at Burlington, where such thinnings have been carried out, a much better distribution of the trees has been effected. The present method employed in many forests of cutting to a diam- eter limit, is inadvisable, because it leaves trees which may be dis- eased, or which may spread the disease, or trees which on the whole are undesirable from the point of view of reproduction or future lum- ber production. Experienced markers should be employed who under- stand the importance of such matters and who would be faithful in attending to the general betterment of silvicultural conditions. Some lumbermen who have become interested in forestry have thought that they could secure reproduction of spruce by leaving trees diseased with red rot for seed purposes, thereby avoiding the financial loss incurred by leaving sound trees. Such procedure is dangerous because it tends to perpetuate the disease, not through the seed of the old trees, but by the fungus upon them. It would be impracticable under existing American forestry con- ditions to attempt such operations as making a complete survey to re- move and disinfect fruiting bodies, unless it were in some valuable grove where expense was not a factor. X. USES OF DISEASED WOOD During the writer's studies of the red rot situation in Vermont lumber yards and mills, certain interesting points were noted as to the methods employed in making use of the diseased wood, as well as to the extent to which the fungus could destroy the wood without totally impairing its value for manufacturing purposes. Red rot lumber, as is indicated in previous pages, is considered worth about $10 per thousand. It is defined usually as "box-board grade." Some manufacturers are able to use it in such ways that they can afford to pay as much as $18 for it. Such lumber often is reserved by dealers for local trade. As a rule it does not pay to ship it. The lumber graded as mentioned above, box-board grade, finds its principal use in the manufacture of boxes of all descriptions. It is not used alone but is mixed with a better grade in order to furnish a marketable product. It is used also in making pails, tubs, kegs, etc. Perhaps this is a more effective method of making use of this wood than that just cited, since much poorer lumber can be used by virtue of the 20 BULLETIN 191 fact that a filler can be employed on the most decayed places and then the whole covered with paint to make an apparently perfect product. The photograph of a butter tub cover in the rough (Plate IV) shows the grade of lumber that can be used and also shows the proportion which can be introduced and still permit the structure to hold together. BIBLIOGRAPHY ' (1) Hartig, R. Diseases of trees. Eng. trans., p. 191, London and New York (1894). (2) Von Schrenk, H. Some diseases of New England conifers. U. S. Dept. Agr., Div. Veg. Phys. and Path., Bui. 25, pp. 31-40 (1900). (3) Lafar, F. Handbuch der technischen Mykologie, Sect, by Tubeuf, C. Holzzerstorende Pilze und Haltbarmachung des Holzes, pp. 286-333, Jena (1904-06). (4) Runnebaum, — . Der Kieferbaumschwamm (Trametes pini). Ztschr. Forst u. Jagdwesen 23, pp. 606-609 (1891). Rev. in Ztschr. f. Pflan- zenkr. 2, p. 242 (1892). (5) Moller, A. Ueber die Notwendigkeit und Moglichkeit wirksamer Be.- kampfung des Kiefernbaumschwamm, Trametes Pini (Thore) Fries. Ztschr. f. Forst u. Jagdwesen, pp. 677-715 (1904). Rev. in Centrbl. f. Bakt. Abt. II, 14, pp. 154-155 (1905). (6) Khan, Abdul Hafiz. Root infection of Trametes Pini. Indian Forester 36, pp. 5^9-562 (1910). (7) Hollrung, M. Jhrsb. ii. Pflanzenkrankheiten 13, p. 305 (1910). (8) Kienitz, — . Kampf gegen den Kiefernbaumschwammes. Ztschr. f. Forst u. Jagdwesen 21 (1906). Rev. in Centrbl. f. Bakt. Abt. II, 17, p. 290 (1907). (9) Borgmann, — . Zur Verwertung von Kiefernschwammholz. Ztschr. f. Forst u. Jagdwesen 39, pp. 594-603 (1907). (10) Oelkers, — . Zur Verwertung von Kiefernschwammholz. Ztschr. f. Forst u. Jagdwesen 42, pp. 754-757 (1910). (11) Von Tubeuf, C. Notizen iiber die Vertikalverbreitung der Trametes Pini und ihr Vorkommen an Verschiedeners Holzarten. Ztschr. f. Land u. Forstwirtschaft. 2 (1906). Rev. in Centrbl. f. Bakt. Abt. II, 17, p. 812 (1907). (12) Hemman, — . Ueber den Schaden des Kiefernbaumschwammes. Ztschr. f. Forst u. Jagdwesen, pp. 239-247 (1905). Rev. in For. Quart. 4, p. 49 (1906). (13) Heinman, — . Ueber den Schaden des Kiefernbaumschwammes. Allg. Forst. u. Jagdzeitung, pp. 123-125 (1908). Rev. in For. Quart. 6, pp. 306-307 (1908). (14) Ziegler, E. A. Average wood production in the United States. Rev. in Fort. Quart. 7, pp. 378-384 (1909). (15) Hedgcock, G. C. Notes on some diseases of our natural forests. Science n. s. 31, p. 751 (1910). (16) Hawley, R. C. and Hawes, A. F. Forestry in New England, p. 122. New York (1912). (17) Graves, A. S. Notes on some diseases of trees in the southern Ap- palachians. Phytopath. 3, pp. 129-134 (1913). (18) Graves, H. S. The Woodsman's Handbook, U. S. Dept. Agr., For. Serv., Bui. 36, pp. 198-199, table 68 (1910). (19) Graves, H. S. Practical forestry in the Adirondacks. U. S. Dept. Agr., Div. For., Bui. 26, p. 31, 47-48 (1899). (20) Spaulding, P. The timber rot caused by Lenzites Sepiaria. U. S. Dept. Agr., Bu. Plant Ind., Bui. 214 (1911). (21) Maxwell, H. Woodworking industries of Vermont. Vt. For. Pub. 11 (1913). (22) Report of the New York State Forest Commission, p. 191, table 15 (1894). (23) Schlich, W. The financial results of forestry. Vol. Ill, Manual of Forestry, p. 124, London (1895). UNITED STATES DEPARTMENT OF AGRICULTURE BULLETIN No. 360 Contribution from the Bureau of Plant Industry WM. A. TAYLOR, Chief Washington, D. C. PROFESSIONAL PAPER June 17, 1916 MISTLETOE INJURY TO CONIFERS IN THE NORTHWEST,1 By JAMES R. WEIR, Forest Pathologist, Office of Investigations in Forest Pathology. CONTENTS. Introduction 1 General nature of the mistletoe injury 2 Result of infection on the branches 13 Result of infection on the trunk 20 Relation of mistletoe injury to fungous at- tack 25 General suppression and fungous attack 27 Page. Relation of mistletoe injury to insects 28 Influence of mistletoe injury on the seed pro- duction of the host 30 Host affinities in relation to silviculture 31 Suggestions for control 33 Summary 37 Literature cited.. 39 INTRODUCTION. It is not generally known that the injury by the mistletoes to coniferous trees in the northwestern United States is such as to assume in many regions the nature of a serious forest problem. The aim of this bulletin is to point out some of the direct and indirect results of this injury. The species of trees most subject to injury are Larix occidentalis (western larch), Pinus ponderosa (western yellow pine), Pinus contorta (lodgepole pine), and Pseudotsuga taxifolia (Douglas fir). Each of these trees is attacked by a particular species of mistletoe of the genus Kazoumofskya (Arceuthobium). With a few exceptions, these species very rarely occur in nature on any other than their common hosts. In the order of the above-named hosts they are Rasoumofskya lands Piper (PL I, fig. 1), R. campylopoda (Engelm.) Piper (PL II, fig. 2), R. americana (Nutt.) Kuntze (PL I, fig. 2), and R. douglasii (En- gelm.) Kuntze (PL II, fig. 1). 1 Thanks are due Mr. E. E. Hubert for assistance In the preparation of the graphs and a number of the other illustrations used in this bulletin. 24182°— Bull. 360—10 1 1 BULLETIN 360, U. S. DEPARTMENT OF AGRICULTURE. GENERAL NATURE OF THE MISTLETOE INJURY. The general nature of the injury to forest growth by these para- sites principally consists sooner or later in a localization and gradual reduction of the assimilatory leaf surface of the host. As will be shown, this is caused by various burl and broom formations on the trunks and branches. The reduction of the leaf surface causes a falling off of the annual increment. During the progress of a study on the larch mistletoe in the Whitman National Forest, Oreg., in the summer of 1913, many data on the retardation of growth of its host by this parasite were assembled^ More recentty, in the lodgepole and yellow pine belt of eastern Washington and northern Idaho, the study Avas continued on these species^ and at frequent intervals on the larch and Douglas fir in the Missoula region of Montana. The method of investigation w-as as follows: Borings from heavily infected (burled and broomed) and uninfected trees were taken with a Mattison increment borer at 4^ feet from the ground, at which point the trees were calipered. With practice the eccentricity of growth due to slope, unequal crown development, injuries, etc., may be very skill- fully judged, so that it is possible to strike the pith of trees within the range of the borer with a fair degree of accuracy. In order to determine as nearly as possible the average radius, in the more doubt- ful cases three borings were taken. On steep slopes the eccentricity of trees may be more accurately judged than on flat land, through the knowledge that more rapid growth takes place on the downhill side of the tree. Height was computed with the Klaussner height meas- urer. Trees of the same species w^ere selected as near as possible from the same type of stand and of the same general age class and the same soil conditions. Only dominant trees free from serious wounds and other possible causes of deterioration were recorded. Finding that the effects of the mistletoe on the increment of the host could be read from the last 40 years' growth of the age classes and conditions of infection selected, Table I was prepared. TABLE I. — The retardation of growtli of forest trees caused by mistletoe, for J^O years, ISl.'f to 1913, inclusive. Host and condition. Basis (num- ber of trees). Average. Age class. Height. Diameter breast high. Total annual growth. Pinus contorta: Infected 50 50 50 50 80 80 40 40 Years. 65 60 100 100 144 144 97 97 Feet. 35.2 48.5 49.5 77.2 63.0 115.0 62.0 73.0 Inches. 6.3 7.8 18.2 22.2 11.5 19.5 17.3 22.2 Inches. 0.93 2.93 1.54 5.33 1.28 2.154 2.175 3.28 Uninfected Pimis ponderosa: Infected Uninfected" Larix occidentals: Infected Uninfected Pseudotsuga taxifolia: Infected Uninfected MISTLETOE INJURY TO CONIFERS. 3 The results in Table I, although based on a relatively small number of trees, prove quite conclusively the effects of mistletoe on the growth of its host. They are graphically shown by the accompany- ing series of illustrations (figs. 1 to 4). A glance at these graphs shows that although there is considerable fluctuation in growth, the line of the uninfected rarely falls below that of the infected trees. These results are not at all surprising when the nature of mistletoe injury is thoroughly appreciated. In a heavily infected region, where all species and ages are more or less involved, dead, dying, or FIG. 1. — Graphs showing the average annual growth (in inches) for 40 years (1874 to 1913, inclusive) of 50 trees of lodgepole pine heavily infected with mistletoe, compared with 50 uninfected trees of the same species for the same period. A, Heavily infected trees : Average-age class, 65 years ; average height, 35.2 feet ; average diameter, breast high, 6.3 inches. B, Uninfected trees : Average-age class, 60 years ; average height, 48.5 feet ; average diameter, breast high, 7.8 inches. weakened mistletoe trees, hastened in their decline by the inroads of fungi and insects, are a common sight. If these trees are carefully examined with respect to the average possible growth for the region, it will be found, as Table I shows, that most of them have died or have become irrevocably weakened or suppressed at a time when rapid or a normal growth should be taking place. This has been found to be true in all regions visited in the Xorthwest where excessive mistletoe infection is common. Infected trees of immature years, pole size and younger, may linger along indefinitely if secondary agents do not appear and may reach an advanced age, but may not attain a merchantable size. Heavily infected and. as a result of this 4 BULLETIN 360, U. S. DEPAKTMENT OF AGKICULTUKE. infection; badly stunted yellow pine, larch, Douglas fir, and lodge- pole pine growing in the open and on otherwise good sites often measure less than 6 inches at the stump, but show ages ranging from 100 to 200 years or more. Young seedlings, if not killed outright within a comparatively short time after infection, usually show a ./& \l /eeo /900 /aos FIG. 2. — Graphs showing the average annual growth (in inches) for 40 years (1874 to 1913, inclusive) of 50 trees of yellow pine heavily infected with mistletoe, com- pared with 50 uninfected trees of the same species for the same period. A, heavily infected trees : Average-age class, 100 years ; average height, 49.5 feet ; average diameter, breast high, 18.2 inches. B, Uninfected trees : Average-age class, 100 years ; average height, 77.2 feet ; average diameter, breast high, 22 inches. marked falling off of the foliar surface of the parts uninfected and finally succumb to the attack (fig. 5). Very frequently young in- fected seedlings develop into ball-like brooms. Table II shows the youngest age class of five hosts at which mistle- toe infection has been found to occur and the locality where the observations were made. MISTLETOE INJURY TO CONIFERS. 5 TABLE II. — The youngest age class of mistletoe infection on five diffrr* nt liosts. Youngest age at Host. which infection Locality where observations were made. is known to occur. Years. Pscudotsugataxifolia 4 Clark Fork Valley, Mont.1 Do 7 Blue Mountains, Oreg. Larix occidentalis 5 Priest River Vallev Idaho Do . 4 Blue Mountains, Oreg. Do 3 Missoula .Mont . Do 7 Sullivan Lake Wash Firms contorta 5 Spokane River, Wash. Do 3 Blue Mountains, Oreg. Do 3 Coeur d'Alene Idaho. Pinus ponderosa ,. 5 Spokane River, Wash. Do 3 Blue Mountains, Oreg. Do 4 Coeur d'Alene, Idaho. Tsuga heterophylla 8 Clearwater River, Idaho. 1 Valleys of the so-called Bitterroot and Missoula Rivers. There is no reason why a seedling should not become infected during its first year if seeds should happen to be favorably located upon it. Seeds falling at the base of terminal buds of yellow-pine branches have been known to effect an entrance in the succeeding I 'o ^ -OS \- 8 .06 s^J £/^* ^ 03 ^.02 \0/ \ \ /<33O /&eS /39O /<3.9S /9OO rrrf&s- FIG. 3. — Graphs showing the average annual growth (in inches) for 40 years (1874 to 1913, inclusive) of 80 trees of western larch heavily infected with mistletoe, com- pared with 80 uninfected trees of the same species for the same period. .1, Heavily infected trees : Average-age class, 144 years ; average height, 63 feet ; average diam- eter, breast high, 11.5 inches. B, Uninfected trees: Average-age class, 144 years; average height, 115 feet ; average diameter, breast high, 19.5 inches. season's growth within the year. All infections of firs and spruces have been found on trees ranging from 50 to 150 years. They occurred principally on the branches, resulting in large brooms, so that nothing could be determined as to the probable age of the hosts when infection took place. 6 BULLETIN" 360, U. S. DEPARTMENT OF AGRICULTURE. Xo evidence is at hand to show that the primary sinker of these parasites can penetrate other than the more tender epidermis of young parts of the host. Germinating mistletoe seeds located on the smooth bark of the Douglas fir or on the irregularities of older stems of yellow pine or larch have never been observed, even after a protracted contact of the disk of the hypocotyl with the surface of the branch, to penetrate the bark. Removing the exhausted hypocotyl and carefully examining the point where the disk was attached, a barely perceptible pit or indentation is sometimes visible, so W \ /e&o /3/O A9/3 FIG. 4. — Graphs showing the average annual growth (in inches) for 40 years (1874 to 1913, inclusive) of 40 trees of Douglas fir heavily infected with mistletoe, com- pared with 40 uninfected trees of the same species for the same period. A, Heavily infected trees : Average-age class, 97 years ; average height, 62 feet ; average di- ameter, breast high, 17.3 inches. B, Uninfected trees : Average-age class, 97 years ; average height, 73 feet ; average diameter, breast high, 22.2 inches. possibly indicating the presence of a solvent, which, however, is ineffective upon more mature bark. There is as yet no proof to sup- port the theory of the presence of a digestive substance which enables the sinker to penetrate the bark more readily. If this were true, infection could possibly occur on older tissues, provided they were not too thick and the food supply in the seed did not become exhausted. As it is, mechanical force, supported by the nonmov- able position of the seed, and irregularities of the stems, such as leaf scales, exits of leaf traces, and leaf sheaths, particularly at MISTLETOE INJURY TO CONIFERS. the nodes and the basal scales of the terminal buds, are the chief factors in the penetration of the primary root. The occurrence of mistletoe plants on the thick-barked branches of old trees or on the main trunk are the result of earlier infection, when the bark was thinner. What appears to be a recent infection on the older parts of trees is often merely a retarded or suppressed condition of an earlier in- fection which has ex- pended most of its energy in the production of a sub- cortical stroma and later breaks through the bark. Periods of suppression and dominance are frequently noticeable in all mistle- toes,^ condition noted to be in several instances di- rectly referable to the state of vigor of the host. An excessive flow of resin sometimes appears in the second and third year of the life of a new infection on larch and yellow pine, which, if not fatal to the young plants, may seri- ously retard their growth for years. Until infection by actual inoculation, using natural methods, is attained, all statements of the ability of the parasite to effect an entrance in old-barked branches or trunks can not be accepted and must be considered faulty observation. The writer has never succeeded in causing the infection of branches at any point older than four years. The ease of infection is found to be more or less in proportion to the decrease in age of the branches tested. This was proved in the case of yellow pine by inserting seeds at regular intervals in the axils of the leaf sheaths of young branches, from the terminal bud to the tenth internode. The results of this experiment are shown in Table III. FIG. 5. — Four-year-old yellow-pine seedlings killed by mistletoe. Note the hypertrophy of the stem at the point of infection and the shortening of the needles. The two seedlings on the right were killed principally by having the wood and cambium in the swelling infiltrated with pitch. The para- site killed the seedling on the left by invading the terminal shoot. BULLETIN 360, U. S. DEPARTMENT OF AGRICULTURE. TABLE III.. — Inoculation of Razoumofskya campylopoda on Pinus ponderosa, made in November, 1911. [x= Inoculation effective; 0= inoculation not effective.] Age of part of branch tested. Seeds sown on each in- ternode. Results in November, 1914, on branch- No. 1. No. 2. No. 3. No. 4. No. 5. Season's growth 10 10 10 10 10 10 10 10 10 10 10 X 0 0 0 0 0 0 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 X X 0 0 0 0 0 0 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 0 X 0 0 0 . 0 0 0 0 0 1 year 2 years 3 years 4 years 5 years 6 years • 7 years 8 years 9 years . ... 10 years A study of Table III shows that the branches were infected in three out of the five test cases on the youngest and last internode on which the seeds were placed. Infection occurred on two of the five tested branches on that part 1 year old at the time of sowing, one infection only being on the 2-year-old portion. Infection did not take place on the older parts of the branches. A tree never be- comes too old for infection to occur on its youngest branches. Sup- pressed trees may escape, owing to the fact that slowness of growth and more rapid formation of thick bark lessens the chance of infec- tion; also shortness of twig growth gives less opportunity. The demand for a fair amount of light is also a factor in such a case, not, however, for the stages of germination and penetration of the primary root, but for the subsequent development of the aerial parts. Mature trees becoming infected on tender branches may not suffer any appreciable injury, but in time the decline of the tree is surely hastened, since the gradually increasing hypertrophy of the branches, the breakages, and the thinning out of the foliage of the tree as a whole cause it to be greatly weakened. Almost always the result of a heavy infection on the trunk and branches of some conifers is the death of the upper portion of the crown,1 causing staghead (fig. 6), 1 The dying back of the crown of trees, commonly known as spikctop, or staghead, is attributed to various causes ; as many, in fact, as the varied conditions under which trees grow. One of the most common theories is that on opening up a stand the admission of light to the trunk and lower crown deflects the transpiration current to the older branch orders or, as with some species, promotes the formation of a secondary crown on the main trunk. This stimulated foliar activity below reduces the water supply at the top of the crown ; consequently the topmost branches die back. This is exactly what happens in the case of mistletoes. The extra crown development below, by brooming, starves out the crown above, resulting in its death. Miinch (Silva, December, 1911, pp. 415-416) claims to have found a parasitic Ascomycete which causes staghead in the oak of Europe by attacking the bark and outer wood of the main shoots. The writer has found a wood-destroying fungus which attacks the upper crown branches of the chestnut in southern Indiana and causes their death. The " pencil rot," which seems to be fre- quently the cause of staghead in the western red cedar, is another example of fungi at- tacking the crown of trees. Lightning is a common cause of staghead ; also injury by insects. Bui. 360, U. S. Dept. of Agriculture. PLATE 1. FIG. 1.— BRANCH OF LARIX OCCIDENTALS INFECTED WITH RAZOUMOFSKYA LARICIS. The staminate and pistillate plants are in close juxtaposition, the former at the end of the twig. FIG. 2.— RAZOUMOFSKYA AMERICANA ON PINUS CONTORTA. Staminate and pistillate plants; long trailing form. Bui. 360, U. S. Dept. of Agriculture. PLATE II. FIG. 1.— RAZOUMOFSKYA DOUQLASII ON PSEUDOTSUGA TAXIFOLIA. Staminate plants, slightly less than natural size. FIG. 2.— RAZOUMOFSKYA CAMPYLOPODA ON PINUS PONDEROSA. The staminate and common con pistillate plants are growing close together on the same branch, a very imon condition for all species, but not generally known. Bui. 360, U. S. Dept. of Agriculture. PLATE III. FIQ. 1.— AN OPEN STAND OF YELLOW PINE HEAVILY INFECTED WITH RAZOUMOFSKYA CAMPYLOPODA. Note that some of the trees are dead and that others have very thin foliage. The structure of the dead brooms is plainly shown. Some of the trees bear burls on the main trunk. The young growth is seriously infected with mistletoe. FIG. 2.— A HEAVY GENERAL INFECTION OF A 1 S-YEAR-OLD YELLOW PINE BY RAZOU- MOFSKYA CAMPYLOPODA, RESULTING IN A DISTORTED AND OPEN CONDITION OF THE CROWN WITHOUT PRONOUNCED BROOMING. The natural excurrent growth of the main trunk is entirely changed. Bui. 360, U. S. Dept. of Agriculture. PLATE IV. FIQ. 1.— NEEDLES OF DOUGLAS FIR FROM A NORMAL BRANCH (AT THE RIGHT) AND OF A MISTLETOE BROOM ON THE SAME TREE, SHOWING THE DIFFERENCE IN SIZE. FIG. 2.— YELLOW PINE AT THE HEAD OF A CANYON, SHOWING MISTLETOE INFECTION. Note that the heaviest infection occurs on the immediate edge of the canyon and that the intensity of the infection decreases as the distance from the brow of the canyon increases ; also that the upper crowns of the infected trees are becoming very thin. MISTLETOE INJUKY TO CONIFERS. 9 or in some cases the entire tree may succumb (fig. 7 and PI. Ill, fig. 1.) In many parts of the Whitman National Forest, wherever the heaviest infection of yellow pine occurs the percentage of dead or spiketopped trees reaches a comparatively high figure. In a report to Supervisor Ireland, Ranger Smith, in referring to the seriousness of the infection of yellow pine in the vicinity of Susanville, Whitman National Forest, states that since 1907, the year in which the mistletoe damage in the region first received at- tention, the infection of all age classes has been growing worse, probably 40 per cent of the stand now be- ing infected. Of the more mature stand, approximately twice as many trees near the station as were noted in 1907 have since died. Ranger Smith further states that for a most pro- nounced general in- fection of all species the drainage basin of the South Burnt River particularly illustrates the devas- tating effects of mis- tletoes. "Almost every yellow pine from seedlings up and Douglas fir above sapling size is heavily infected and most of the mature timber shows great retarda- tion of growth and is now adding little or no increment. This infection covers a large part of the best yellow-pine sites in the yellow-pine belt of this watershed." This region was not visited by the writer, but to judge from studies in other parts of the same forest Ranger Smith's observations are undoubtedly correct. In order to determine the relative amounts of different species cut as snags on the W. H. Eccles Lumber Co. sale (whitman Xa- 24182°— Bull. 360—16 2 FIG. 6. — Douglas fir, showing the death of the upper por- tion of the crown caused by Razoumofskya douglasii. The tree to the right with the series of immense brooms also has a dead top. A large broom had split off from the trunk of the tree on the left. All the young growth in the vicinity of these trees is seriously infected. 10 BULLETIN 360,, U. S. DEPARTMENT OF AGRICULTURE. tional Forest), the following figures were assembled by Mr. T. J. Starker, covering a period of 28 days of cutting : Western larch 556 Western yellow pine__ 1, 221 Douglas fir — Total - 2, 199 It must not be assumed that the death of these trees resulted from mistletoe. It is doubtful whether the death of even a small percentage of them, with the exception of the larch, can be so referred. A more conservative statement would be that mistletoe had a large share in their death by causing spiketop, the brooming of branches, and the formation of burls on the trunk. These are com- mon forms of mistletoe in- jury for all three species in this region and lead up to serious insect infestation, of which more is said later. That mistletoes are capable of actually causing the death of their hosts is first shown by their effects on young growth from three to eight years old. In a heavily infected but very open stand of yellow pine on the bench lands of the Spokane River, Wash. (PI. Ill, fig. 1), an attempt was made to ascertain the 'amount of injury resulting to the seedlings of an aver- age sample acre, which included in its area nine semimature and heavily infected trees in all stages of suppression. The acre was divided into plats and all young growth counted and examined as to infection and the condition of the infection. The number of seedlings and small growth below 8 feet in height totaled 480, which is an excellent reproduction for this region. Just a little more than half of this number, or 245, were found to be infected, representing every possible type of infection on stem and branch. It is not to be expected that these seedlings would ever grow up to form merchant- FIG. 7. — Douglas fir killed by mistletoe. Note the total absence of normal branches. The structure of the brooms is here plainly shown. Note the straight trunk of the larch in the background. It is uninfected by mistletoe and still retains its original branches. MISTLETOE INJURY TO CONIFERS. 11 able trees. Considering the severity of the infection, they could not be expected to attain near the size of their parents shown in Plate III, figure 1, and from which they received the mistletoe. Of the 245 infected seedlings, 49 were dead. An examination of the root system of each seedling showed it to be well developed. In the absence of any other deteriorating influence except an occa- sional needle infested by Chionaspis pinifolia Fitch, the death of these seedlings must be ascribed to the lux- uriant growth of mistletoe which they had supported (fig. 5). In most cases the tufts of mistletoe had fallen away. The bark of the large fusiform swellings was usually ruptured and both the wood and bast tis- sues were so heavily infil- trated with pitch that the passage of food materials between the crown and the roots was wholly impossible, resulting in death. In this respect there is a parallel between this type of mistle- toe injury to seedlings and that resulting from the perennial mycelium of some caulicolus Peridermiums. A further study of the large trees shown in Plate III, figure 1, is illuminating. Two of them, the right and the left in the figure, are dead. Scarcely a single normal branch is to be seen, but instead are numerous large gnarled and distorted brooms. These trees measured on an average 9.3 inches in diameter at 44 feet from the ground, and increment borings showed the age of each to be 190 years. This is far below the diameter of normal trees of the same age for the region. A careful search for secondary causes of injury resulted negatively. The trees were absolutely sound. Lightning injury, which sometimes causes spiketop in yellow pine and other conifers and which sometimes is erroneously attributed to mistletoe, was not present. With the evidence in hand, it is safe to state that the trees FIG. 8. — A group of Douglas firs with their entire lower crowns developed into brooms by Razou- mofskya douylasii. Note the sparse foliage of the upper crowns and the young brooms in the tree on the right, showing how the parasite travels upward. The branches between the brooms have died from lack of nourishment. 12 BULLETIN 360, U. S. DEPARTMENT OF AGRICULTURE. • were killed by the parasite. The other trees in the figure show various stages of suppression and an abnormal thinness of foliage, The tree on the extreme right shows midway on its trunk a typica] mistletoe trunk burl. It is often disputed that mistletoe is a cause of spiketop or that it is totally unknown for some species. The first and heaviest seat oi infection in nearly all trees of economic importance is in the lower part of the crown (figs. 6 and 8). This is not necessarily a result oi the seeds of the parasite falling first on the lower branches, but is rather the result of the fact that the main shoot continues for a time to grow in height, and the crown may attain its normal height be- fore the effects of the parasite become dominant. The mistletoe spreads upward from the lowermost branches, with the result thai the more recently formed branches are continually being infected That these infections may not cause a brooming of the branches ir the beginning is abundantly shown by the entire absence of anj brooming on young infected branches of several host species. This however, is only the first stage in the hypertrophy of the branch, After the lapse of several years, typical brooms are formed. With the increasing hypertrophy of the lower portion of the crown, food materials are more and more appropriated at this point. The result is a drain on the resources of the entire tree to support the brooms, Materials traveling upward from the roots are likewise utilized b} the broomeo! branches, with the result that the upper portion of the crown starves and in cases of severe infection finally dies (figs. 5, 6 7, and 8). Spiketop is an almost universal condition in heavily infected larch. The tendency to form spiketop in this species, how- ever, is greatly augmented by the brittleness of its branches. Douglas fir probably comes next in order of frequency of dead tops resulting from the growth of mistletoes. The condition is common for yellow pine in all regions where observations have been made by the writer and is reported to be of frequent occurrence by correspondents in Utah and Wyoming. Lowland and mountain hemlocks, when heavily infected, quite commonly exhibit dead tops. An unusual case oi heavy infection of the former species was studied in the St. Joe Xational Forest. Practically every tree in the entire stand was dead in the top (fig. 9). Lodgepole pine is less affected in this manner than any other conifer so far studied by the writer except spruce and fir. The last-named species are so seldom infected, however, that they would not enter into the discussion. There can be little doubt that spiketop is very often the result of heavy mistletoe infection, but varies in degree for the several hosts. This condition is of importance, since the proportion of snags in the stand is thereby increased, which may promote injury by fungi and insects; it also increases clanger from lightning fires. MISTLETOE INJURY TO CONIFERS. 13 With the conclusion of this general statement of mistletoe injury a more detailed discussion of the various types of infection will now be taken up. RESULT OF INFECTION ON THE BRANCHES. One of the first effects of infection, either of stem or branch, is the formation of a fusiform swelling (fig. 10). Sometimes this swelling is very pronounced and may resemble the enlargements caused by some species of Peridermium (fig. 11). The swelling is the first stage of the future hypertrophy commonly known as witches'-brooms. The absence of any pro- nounced brooming from early infections has led some observers to the conclusion that brooms are never pro- duced on some conifers. Any change from the normal branching is here considered a broom. Still it is not necessary to draw such sharp lines, as the brooms produced by all mistletoes of the genus in question are quite typical. It may re- FIG. 9. — Western hemlock (Tsuga heterophylla) infected quire Several years for by Ra~oum°fsjcya tsugensis. These trees do not possess a single normal branch. All are broomed. The trees in the broom to form. If the background are spike topped. The tree in the fore- VOUnff trees are ffen- gr<>und has hajl its growth in height arrested by an immense terminal broom. erally infected they sometimes assume an open, ragged appearance, which to the casual observer would not be considered a broom (PI. Ill, fig. 2). Never- theless, the tree is no longer excurrent. A similar condition is sometimes noted in more mature larches, where the infection is so generally distributed throughout the entire crown that no typical brooms are produced for years. Heavily infected branches of old trees of all species are seldom without brooming of some kind, and in most cases typical brooms are formed. The mistletoe plant may die out entirely on very old brooms, especially those of yellow pine 14 BULLETIN 360, U. S. DEPARTMENT OF AGRICULTURE. (fig. 12). but the stimulus to abnormal branching may continue. Brooms are formed on all hosts attacked by this genus of mistletoe. Those of the yellow •f pine, owing to their loosely branched con- dition (fig. 12), are sometimes not as con- spicuous as those pro- duced on Douglas fir (figs. 6, 7, and 13), larch (fig. 14), hem- lock (fig. 9), or lodge- pole pine. In all the regions where the yellow-pine mistletoe has been ob- served in the States of Washington, Oregon, Idaho, Montana, and South Dakota, broom- ing is a common result of the growth of the parasite on this tree. Correspondents in "Wy- oming, Utah, and Colorado report that old infected trees are seldom without them. MacDougal (8)1 refers to the excessive brooming of yellow pine by mis- tletoe in the South- west. Meinecke (10) refers to the very conspicuous brooms on Jeffrey pine, sugar pine, yellow pine, lodgepole pine, and Douglas fir. The old brooms of the Douglas fir, be- cause of the long, trailing, willowlike branches of the lower portion of the broom, are more con- spicuous than those of other conifers (fig. 13). They sometimes attain an immense size, often including the entire crown (fig. 6). In FIG. 10. — Young, first infections of RazoumofsJcya cam- pylopoda on western yellow pine (Finns ponderosa). FIG. 11. — A larch branch, showing the result of a first infec- tion at its base by Razoumofskya laricis. Ihis is the be- ginning of a burl at this point, which will spread to the main trunk. 1 Reference is made by number to " Literature cited," p. 39. MISTLETOE INJURY TO CONIFERS. 15 most cases brooms are initiated on the Douglas fir soon after infec- tion. Young seedlings frequently die in the top, owing to the forma- tion of a lateral broom midway on the stem. In the heavily infected regions of Montana, especially in the Clark Fork (Bitterroot and Mis- soula Rivers) drainage, brooming of the Douglas fir is so universal and of such extent that scarcely a single infected tree is free from brooms of some type (figs. 6 and 7). The structure of these brooms is very plainly shown if the tree succumbs to the parasite, as it often does (fig. 7). The formation of brooms invariably results from mis- tletoe infection on the western larch. They may be situ- ated on any part of the branch or at its base (fig. 14). In the latter case the entire branch even- tually dies or is broken off by the wind, and its place is usually taken by a series of short, scrubby secondary branches forming a trunk broom. This broom eventually dies, leaving a large knotty burl of seri- ous consequence not only to the life of the tree but greatly decreasing its value for lumber. Excessive brooming is a common feature wherever infected larch occurs and is the chief cause of injury to the species. In some localities in the Blue Moun- tains of Oregon and parts of Idaho and Montana, where this mistletoe is common, a normally formed larch is seldom found. Instead of the symmetrical, conical crown so characteristic of the normal tree, the crown develops under the influence of the parasite into a denuded spike, bearing only a few ragged branches. When it is recalled that practically every larch in these regions, from pole size up, is more or less infected and seldom attains a normal size, in many cases being killed outright, some notion may be had of the seriousness of the effects of the parasite on its host. FIG. 12. — Typical broom on yellow pine caused by Razoit- mofskya campylopoda. Note that the end of the branch is dead. 16 BULLETIN 360, U. S. DEPARTMENT OF AGRICULTURE. The brooming of the branches of the lodgepole pine by mistletoe is as characteristic as for the other hosts mentioned. Frequently the entire tree is involved, but more often only the lower branches. A f ew instances have been noted where the parasite hung in long festoons from the sev- eral infected branches FIG. 13. — Typical broom of the weeping-willow type on Doug- las fir caused by Razoumofskya douglasii. Note the long, flowing branches. Sometimes these branches are 8 to 10 feet long. without any particular hypertrophy of the branch as a whole. This condition is more apt to occur in dense stands. Observations by the writer on Picea engelmanni, P. mariana, Abies grandis, A. lasiocarpa, A. concolor, A. magnified, Tsuga heterophylla, T. merten- siana, Pinus monticola, P. alUcaulis, P. flexi- lis, P. attenuata, and other conifers show that brooming of the branches is a common phe- nomenon attending mistletoe infection of these species. The weight of these brooms on many coni- fers is frequently sufficient under stress of winds and rain to cause the branches to split from the trunk, or to break farther out if the brooms are located far out from the trunk. This very commonly occurs in the case of FIG. 14. — Typical brooms of old infections on western larch caused by Razoumofskya lari- cis. Very few of the origi- nal branches remain, and they are heavily broomed and covered with lichens. The old branches are replaced by short scrubby secondary branches. Note that two of the original branches still re- main, but are dead. MISTLETOE INJURY TO CONIFERS. 17 yellow pine and Douglas fir (fig. 15) and is the rule for larch. The stunting effect of these brooms on the trees as a whole was in one instance very interestingly shown by the fact that a middle-aged Douglas fir increased the radial dimensions of its annual rings after the removal by the wind of an immense broom located midway on the trunk. The weight of the brooms on some conifers is very often greatly increased by the accumulation of dead needles, lichens, etc. (fig. 11). When loaded with snow or saturated with moisture the brooms are more easily broken off by high winds. The ground around the base of heavily in- fected larches is very frequently littered with brooms broken off in this manner, often insuring the death of the tree in case of ground fires. During the early part of October, 1914, an unusually heavy fall of soft snow occurred locally over a small area around Missoula, Mont. The snow ac- cumulated in such quantities on the mis- tletoe brooms of the larches and Douglas firs throughout the area that the ground around the more heavily infected trees was piled high with fallen brooms. The foliage of old and mature mistletoe brooms is usually not as long lived as that of normal branches of uninfected trees. This is not true in the case of young well-nourished brooms. It has been observed to any extent only in old brooms which have begun to tax the food supply of the tree or the branch on which they are located. In the course of one year it was determined that 655 more needles fell from a small but mature broom on a Douglas fir than from a normal branch of a neighboring uninfected tree of the same species. The number of needles falling from the broom totaled 24182°— Bull. 360—16 3 FIG. 15. — Fallen brooms split from the trunk of a Douglas fir and piled about the base of the tree — a serious fire menace. 18 BULLETIN 360, U. S. DEPARTMENT OF AGRICULTURE. 976, from the branch 321. On very old brooms of the western larch it is often noticed that the needles begin to turn yellow some time before those on the branches of uninfected trees. Exactly the re- verse may occur in the case of recently formed brooms, owing to the larger amount of newly stored food materials in the swelling on the main branch and the branches of the brooms. That the broom may be the cause of a great localization of food substances is indicated by the fact that in heavily infected Douglas fir and larch the last part of the tree to succumb is usually the smaller and younger brooms of the tree. Frequently trees of these species are noticed with only a single small broom living, the rest of the branches being apparently dead; likewise the old and exhausted brooms. The increase in the number of needles on the broom due to the multi- plication of its branches is usually at the expense of the needle de- velopment on the normal parts of the tree. For this reason an excess of food materials for the tree as a whole does not take place. The foliage beyond the broom becomes thin and, in most cases, the end of the branch dies (figs. 12 and 14). The food materials • are entirely stored and appropriated by the broom itself. The phenomenon is analogous to the formation of spiketop of the main trunk. That brooms do not always necessarily mean an increase in foliar surface for the host, since we have seen that parts of the branches not supporting brooms frequently die, is shown by a comparison of the needles of old brooms with those of normal branches either of the same tree or of uninfected trees. Such a study was made in the case of the Douglas fir. It was found that the needles of the brooms on the trees studied were uniformly a little less than one-half as long as the leaves of the normal branches (PI. IV, fig. 1). Neither were they as thick or as broad. By compensation it would be possible to determine approximately the actual foliar surface of a given broom and compare it with that of a given normal branch of the same whorl and of the same age. This difference in the size of the needles was found to hold good only in the case of old, mature brooms of trees which were beginning to be suppressed. Young brooms, especially on young trees from 10 to 20 years old, often have abnormally long needles on the still upright branches, but this condition is not long maintained. Soon these branches begin to droop, the broom be- comes denser, the needles disappear from the center outward, and they are often sparingly distributed along the stems but more densely assembled on the last few years' growth (fig. 13). With continued suppression of the Douglas fir and exhaustion of the broom, a new type of branching often appears. The long trailing, weeping-willow- like branches cease to elongate and the cortical stroma of the parasite is enabled to catch up with the terminal bud and kill it. The branch MISTLETOE INJURY TO CONIFERS. 19 ceases to grow in length and instead forms abnormally abundant lateral branches. The terminal buds of these are likewise overtaken by the parasite, resulting in additional lateral branches, and so on, until a type of dichotomous branching results. This is more notice- able in the compact type of broom than in the long, trailing type, but is quite common in both, especially on exposed and wind-swept areas. A very interesting hypertrophy of the foliage spurs is often shoAvn by the brooms of the larch. The spurs are frequently abnormally large and may be four or five times as long as those of normal branches (fig. 16). On such spurs the needles are usually shorter and spar- ingly clustered. Eventually the para- site enters the spur and kills it. Not in- frequently a mistle- toe plant is found growing out at the apex of the spur or from its side, caus- ing great distortion and the total disap- pearance of the nee- dles, and eventually the death of the spur. The reduction of foliage by the thin- ning and shortening of the needles of the trees as a whole, and of the brooms sooner or later, is characteristic of mistletoe infection on all hosts. The food material, which undoubtedly is accumulated in the brooms, seems to be entirely appropriated at these points and does not serve the host as a whole. The support of the excessive number of branches is necessary, but the parasite itself undoubtedly appro- priates a large share at the expense of the healthy branches. The yellow-pine mistletoe has been observed to become more luxuriant and to develop abnormally long stems on swellings which had been lacerated or gnawed by rodents. Evidently the accumulation of FIG. 16. — Abnormal foliar spurs of the western larch caused by Razoumofskya laricis. Note their size as compared with normal spurs. 20 BULLETIN 360, U. S. DEPARTMENT' OF AGRICULTURE. extra food materials in the healing tissues at this point exercised a beneficial influence on the parasite. The actual nutritive relation between these parasites and their hosts is not at present well understood. The constant removal of all the needles of six lodgepole pines 8 to 12 years old on which large clumps of mistletoe were attached has not in the second year of the experiment resulted in the death of either the host or parasite. The controls, viz, six young pines of the same age, stripped of their needles but bearing no mistletoe plants, have died. This experi- ment indicates a possible transfer between the host and parasite not only of water and inorganic salts, but of or- ganic food materials as well. However it may be interpreted, it seems that the pines were kept alive temporarily by the mistletoe. Probably it is a mutual subsistence on stored materials. It must be remembered that the whole tendency of the activities of these mis- tletoes (Razoumofskya spp.) is to reduce the life functions of the host to their lowest point, and this is the fact that should be of chief concern to the forester. RESULT OF INFECTION ON THE TRUNK. Another form of mistletoe injury results when infections occur during the early life of the tree, with the formation of burls on the trunk. No case is on record of any mem- ""enow "So ber of the genus Razoumofskya effecting an infected by Rasoumofskya entrance to its host through the mature cor- &£&**£& tex- If "PParently recent infections on old location of the burl tis- parts of trees are carefully examined, the ~i&rj?>£Sri mistletoe plant will be found to have per- the illustration were pres- sisted from the time when the branch or trunk was young. Until it is proved by actual inoculation that the parasite is able to penetrate the mature cortex with its outside covering, commonly called the bark, the fore- going statements must remain valid. Burls on the trunk caused by mistletoe are very common for some hosts, but vary in frequenc}^ on others. In point of frequency the western larch is most seriously affected by this kind of injury. Two types of burls occur on this tree, determined by the nature of the original infection. If the infection occurs at the base of a branch (fig. 11) arid travels to the main trunk, a basal branch burl results, giving rise to a broom, which later dies, leaving a great burl, often of large proportions. If infection occurs directly on the main trunk the beginning of a trunk burl is immediately initiated. With MISTLETOE INJURY TO CONIFERS. 21 the increasing age of the host the burl tissues radiate outward in a fan-shaped area when viewed in cross section and soon leave an open wound, through the death of the central part of the infected wood. These two types of burl are so common on larch in mistletoe regions that the quality of the wood is seriously injured, resulting in a large amount of cull. In the several regions studied by the writer mistletoe burls on yellow pine are frequent. In one section of the city park at Coeur d'Alene, Idaho, are 30 or 40 large, old yellow pines. About half of the trees have mistletoe burls on the first FIG. 18. — Cross section of a mistletoe burl on the yellow pine shown in figure 17. (The tape shows feet in tenths.) log length and in most cases the parasite is still living in them, with a few scattering short aerial parts. Similar conditions pre- vail throughout the Spokane River Valley and around Coeur d'Alene Lake. Mistletoe burls on old yellow pine may or may not be con- spicuous. Frequently there is no pronounced swelling (fig. 17) and sometimes the only means of detecting the diseased condition is by the presence of the mistletoe or an unusual roughness of the bark. A section through the tree at this point, however, shows the curly grain and the old roots of the parasite extending to the point of original infection (fig. 18). These burls are often very conspicu- 22 BULLETIN 360, U. S. DEPARTMENT OF AGRICULTURE. oils, large barrel-shaped swellings, from which pitch usually exudes in large quantities. Infection on one side of the tree generally re- sults in the type of burl shown in figure 19. Burl formations resulting from mistletoe are a common feature FIG. 19. — Common type of burl on yellow pine caused by RazoumofsJcya campylo- poila. The tree is 3 feet in diameter at this point. on western hemlock wherever the parasite occurs in quantity. The same is true for the mountain hemlock. In the Marble Creek region of the St. Joe National Forest mistletoe burls on the hemlock are of frequent occur- rence. Allen (1, p. 20-21) writes of this type of injury as follows: " If, however, the plant gets foothold on the leading shoot, a burl follows which persists throughout the life of the tree and not only ruins a log, but ren- ders the tree apt to be broken by the wind." Infection on the main trunk of lodgepole pine is often attended by long fusiform swell- ingS as the parasite . progresses from the Original point of in- fection. This may Continue Until the bark becomes so hard that the plants can not push up through it and the spread of the parasite ceases (fig. 20). The parts tne spread of the parasite from the original ^erffrfquenUy'dL, ^avin^an^pen wound* (Photographed by George G. Hedgcock.) MISTLETOE INJURY TO CONIFERS. 23 infected, however, may continue to produce aerial branches of the mistletoe to a very advanced age. True mistletoe burls are probably of less frequent occurrence on Douglas fir than on any other economic tree species. Burls do occur, however, with sufficient frequency to be characteristic of mistletoe infection on the trunk of this tree. Large elongated mistletoe burls, including the entire circumference of the trunk, occasionally occur in heavily infected trees in many parts of Idaho and Montana (fig. 21). More frequently there is a series FIG. 21. — Large mistletoe burl on Douglas fir caused by RazoumofsTcya douglasil. This burl is approximately 10 feet long and 2 feet in diameter at its widest part. FIG. 22. — A Douglas fir, showing numer- ous burls caused by Razoumn/skya douglasii. The branches are heavily broomed. A high degree of infection, but a common condition, is shown. of individual burls, more or less confluent, on one trunk (fig. 22), each burl representing the seat of an old infection, from which the aerial parts of the parasite have long since disappeared. Longitu- dinal and cross sections through these burls show the characteristic fan-shaped areas of infection (fig. 23). In numerous cases the burls originate from infections at the base of branches. If the branch dies or is broken off, an open wound is formed in the center of the burl. Very peculiar swellings or small burls frequently occur on 24 BULLETIN 360, U. S. DEPARTMENT OF AGRICULTURE. the branches of brooms. These are sometimes so numerous as to cause the branch to resemble a chain of spherical balls. Mistletoe infection on the trunks of spruces in the East often results in the formation of burls; also on the western firs. It can be safely stated that swellings and distortions of the main trunk which persist throughout the life of the tree are a characteristic feature of mistle- toe infection on most conifers of economic importance. The spread of the burl tissues tangentially and longitudinally, which, as previously indicated, are frequently inhabited by the FIG. 23.— Cross section of one of the burls on the Douglas fir shown in figure 22. This section does not pass through the point showing the age at which the infection first occurred. (The tape shows feet in tenths.) parasite until a very advanced age,1 results, as is the case with most species, in cutting off the transporting tissues and hastens the de- cline of the tree (figs. 20, 23, and 24). The bark and wood of the 1 Meinecke, in 1912 (9, p. 38), records the age of a mistletoe plant (Phoradendron junipcrinum libocedri Engelm.) at approximately 230 years. Species of the genus Razou- mofskya are likewise capable of maintaining themselves to a very advanced age. One instance recorded by the writer may be cited of RazoumofsJcya campylopoda. A cross sec- tion through a mistletoe burl of this species, 3 feet from the ground, on yellow pine — a po- sition precluding any but an original infection at an age when the bark was thin — showed that the parasite had continuously lived in the burl tissues for 340 years. The old roots, now dead except those immediately next the cambium, could be readily traced to the point of original infection The age of the tree at this point was three years. The burl bore a single fertile aerial branch of the mistletoe. The greater mass of the cortical stroma was entirely without aerial parts, indicating the remarkable condition of parasitism first pointed out by Meinecke for Phoradendron juniperinum libocedri. MISTLETOE INJURY TO CONIFERS. 25 outer central area of the burl die soon after the death of the cor- tex, especially in burls on the larch, and open wounds are formed, inviting the attack of forest-tree insects and wood-destroying fungi (fig. 24). The abnormal thickness and the soft, spongy consistency of the inner bark of mistletoe-infected branches are attractive to various gnawing animals; they are also an index of the storage of food materials at this point (fig. 25). PIG. 24. — Cross section of a burl on a western larch caused by Razoumofskya laricls. Diameter of burl, 2 feet. Note the presence of borers and fungi. The check ap- peared in seasoning. RELATION OF MISTLETOE INJURY TO FUNGOUS ATTACK. Some very interesting data have recently been assembled by the writer on the relation of mistletoe burls to fungous attack. From cutting areas on the dry bench lands of northern Idaho, 540 mistle- toe-infected living larches were examined. Out of 600 mistletoe burls found on these trees, 278 were inhabited by serious wood- destroying fungi and other unimportant species. According to frequency of occurrence the most important of these fungi are Trametes pini (Brot.) Fr., Fomes laricis (Jacq.) Murr., Polyporus sulphureus Fr. (four occurrences at 20 feet up on the trunk, a very 26 BULLETIN 360, U. S. DEPARTMENT OF AGRICULTURE. unusual habitat), Trametes serialis Fr., and Lenzites sepiaria Fr. Fomes pinicola Fr. was found rotting the heartwood of living trees in three different cases and had entered its host through mistletoe burls 10 feet from the ground. Polyporus volvatus Pk. occurs fre- quently on the burls of larch and yellow pine. Several species of Thelephoraceae were collected from the mistletoe burls, chief of which were Stereum sulcatum Burt, Corticium "berkeleyi Cooke, C. galactinum (Fr.) Burt, and Peniophora s u l> s u I - phurea (Karst) Burt. Cera- tostomella pilifera (Fr.) Wint., the bluing fungus, appeared occasionally in the dead wood of the burls. Trametes pini affected 80 per cent of all burls attacked by fungi. Since the most advanced stages of decay were always at the burl or in its near vicinity, it was as- sumed that the fungi had en- tered at this point. The de- cay at or in the burl tissues was in most cases not con- nected with the decay which is often present in other parts of the trunk. The breakage of old branches possessing heartwood, through the accumulation of brooms at their outer ex- tremities, is likewise a means of fungi entering the tree. Not infrequently F o in e s laricis enters its host by this means. Mistletoe burls on Douglas fir are known to become infected with Trametes pini. A mistletoe burl on Alpine fir was found to be inhabited in one instance by Pholiota adiposa Fr. Meinecke (10, p. 58) refers to the mistletoe cankers of Abies concolor as offering an easy entrance to germinating spores of EcMnodontium tinctorium. Burls on yellow pine, owing to their resinous condition, are seldom attacked by wood-destroying fungi. The bluing fungus, however, has been found by the writer in the distorted tissues of mistletoe burls on living yellow pine. FIG. 25. — The soft spongy cortex of a mistletoe infection on lodgepole pine gnawed by rodents. This is a very common type of injury in mistle- toe-infected trees. MISTLETOE INJURY TO CONIFERS. 27 GENERAL SUPPRESSION AND FUNGOUS ATTACK. Aside from the fact that fungous enemies enter these conifers through broken branches, lesions, and burls caused by mistletoe, heavily infected trees are, owing to their weakened condition, more susceptible to fungous attack on any part — roots, trunks, or leaves. In the lake region of Idaho the larch of all ages and conditions is at present suffering from an epidemic of a needle disease, Hypoder- mella laricis Tub. It is observed that in practically every instance the needles of very old mistletoe brooms are first attacked, whereas those of the uninfected trees of particular age classes or exposures may ward it off for a longer period.1 It is a common observation that in regions of heavy mistletoe infection (and no\vhere is it better shown than in the forests of eastern and central Oregon and many parts of Idaho and Montana) many heavily infected trees are in a dead and dying condition. If these trees are carefully examined with reference to average healthy growth for the region, it will be found that they have died prematurely. It has already been indicated that mistletoe is capable of causing the death of its host in some instances. The whole tendency of the parasite is to reduce the life functions of its host to the lowest point, and if death does not result from this cause alone the way is opened to various secondary agents, which may or may not attack vigorously growing trees. The gradual thinning out of the foliage of heavily infected trees and the appropriation by the brooms of much of the elaborated food materials must necessarily result in an unbalanced relation between the crown and the root system. Consequently, there may be a dearth of food materials for the latter, wholly inadequate to support its present extent. It may be naturally inferred that this results in the suppression of the roots or a dying off of the more extended members of the system. A close examination of a hundred or more windfalls of heavily infected Douglas fir, yellow pine, and larch in the regions above mentioned shows quite clearly that the horizontal and brace roots of these trees in most cases were badly decayed. Since few windfalls of the heavily uninfected trees of the same average age and size were observed in the same region, it may be inferred that a possible relation existed between the sup- pressing effects of the mistletoe and the decay in the roots. Armil- laria mellea (Yahl.) Quel. was definitely associated with some of the decay in the roots. In most cases, however, owing to the absence of fruiting stages, the cause of the rot in the fallen trees could not be determined. 1 Hypodermella laricis was first named and described by Von Tubeuf on the European larch (Larix curopaea} . This is the first note of its occurrence in North America. The fungus, characterized by its four clavate spores to an ascus, is very destructive and is the cause of considerable damage in the larch forests of the northwestern United States and Canada. 28 BULLETIN 360, U. S. DEPARTMENT OF AGRICULTURE. It is a well-known fact that wounds heal quickly in young or in strongly growing trees, principally due to the protection afforded by an abundant flow of resin. It may be assumed that trees having their life functions brought to a low ebb by excessive mistletoe infections, with resulting decrease in annual increment, will not be able to heal or protect their wounds as quickly as normal trees ; hence, are more liable to infection. This may be one of the reasons why so many open burls are formed on infected larches. These open burls are seldom, if ever, healed, although the parasite in its tissues has long since died. There is a slight increase in the number of resin passages in early burl formations, but this*s entirely offset by the early dying out of the bark of the burl exposing the wood. It is an observed fact, experimentally proved by the writer, that strongly suppressed yellow pine, larch, and Douglas fir do not as readily form traumatic wood or exude the normal quantity of resin on being wounded on any part as do normal, healthy trees. Such a tardy reaction to injury does not afford a ready antisepsis against the entrance of fungi which may attack these trees. Since turpentine orcharding is becoming more extensively practiced in the West it would be an interesting experi- ment to determine the relative flow of pitch from trees strongly sup- pressed by mistletoe and from those in a high state of health. RELATION OF MISTLETOE INJURY TO INSECTS. In the same manner that burls and other types of mistletoe injury on some conifers are open doors to fungi, they are found to afford a ready means of entrance for some species of forest-tree insects which do not in this region habitually attack vigorous unwounded trees. Old mistletoe burls on larches are almost invariably attacked by borers (figs. 23 and 24), and burls on yeliowr pine are, in the ex- perience of the writer, quite as frequently infested by bark and wood boring beetles. In this connection a very curious and interesting phe- nomenon often occurs on young yellow pines from 10 to 20 years of age. An infection by mistletoe will have occurred, completely enveloping the trunk some 2 or 3 feet from the ground. The parasite having advanced somewhat each way from the point of original infection, the intervening space is attacked by Dendroctonus valens Lee. The combined influence of the beetle and mistletoe results in the complete infiltration with resin of the space between the two edges of the advancing mistletoe, so that the cambium dries out and dies. Strange to state, this does not always kill the tree. The crown goes on manufacturing food materials, being supplied with water through the inner wood of the girdled area. The elaborated food not being able to travel downward, since the cambial tissues of the entire cir- cumference of the stem have been destroyed, is stored just above the MISTLETOE INJURY TO CONIFERS. 29 girdled area and initiates an abnormal swelling (fig. 26). The swell- ing continues to increase in size and weight, likewise all members of the crown, so that eventually the slender stem below can no longer support the overdeveloped crown and is broken down by the wind. A specimen in the laboratory shows the number of rings of the stem at the girdled area at the time it was cut to be eight, with a diameter of 1 inch. The swelling just above and within the same internode showed 15 rings, with a diameter of 3 inches. The same phenomenon is sometimes produced in yel- low pine by Peridermium fila- mentosum Pk. When it is re- called that the cambium and the outer wood of the girdled area are actually dead, the length of time the crown con- tinues alive is really remark- able. In point of general insect at- tack it has been noted that the beginning of an infestation may start with trees badly suppressed by mistletoe. The fact that trees heavily sup- pressed by mistletoe have a weak flow of sap causes them to be first selected by certain forest-tree insects. For this reason mistletoe areas form centers from which infesta- tions may spread. Again, nu- merous infestations may start simultaneously over a wide territory, owing to the weak- ening of the trees by these par- asites instead of from a few detached areas, as is often the case. This has been found par- ticularly true in the case of yellow pine and the red turpentine beetle mentioned above. In all regions of heavy mistletoe infection of the Douglas fir, Dendroctonus pseudotsuga Hopk. is usually very abun- dant. This was the rule in the Whitman National Forest, Oreg., and though the numerous dead trees of this species in the forest were undoubtedly the result of an immediate attack by the beetles, their work was hastened, it seemed, by the serious mistletoe suppression which was exhibited by most of the dead trees. During the season PIG. 26. — A young yellow pine, showing com- plete girdling of the stem by a combined at- tack of mistletoe and insects. The cambium is destroyed, but the crown remains alive and continues to elaborate food materials, which are stored just above the girdled area. 30 BULLETIN 360, U. S. DEPARTMENT OF AGRICULTUEE. of 1914, a large number of badly suppressed Douglas firs on the foot- hills bordering the Clark Fork (Missoula River) Valley have died from a combined attack of mistletoe and beetles. Most of these trees, which supported scarcely a single normal branch, had the bark of limbs and trunk almost entirely removed by woodpeckers in their search for the beetle before the leaves were entirely dead. The few uninfected Douglas firs of the same region have not been attacked by the beetles. The branches of large mistletoe brooms on yellow pine and Doug- las fir from which the parasite has entirely disappeared are very FIG. 27. — Seats of original mistletoe infection on two living branches (in center and at left) of mistletoe brooms on yellow pine infested with bark beetles. No other part of the broom or tree was attacked. Main stem of young living yellow pine (at right) attacked by bark beetles at the seat of an old mistletoe infection. frequently found infested with bark beetles (fig. 27), while the trunk and normal branches of the trees are entirely free from attack. INFLUENCE OF MISTLETOE INJURY ON THE SEED PRODUCTION OF THE HOST. Germination tests of seeds of yellow pine taken from mistletoe- infected trees show that the percentage of germination is consid- erably lower than is the case with seeds taken from normal trees (12, p. 7). Experiments conducted by the writer with seeds taken from cones produced on very old mistletoe brooms of Douglas fir, larch, and lodgepole pine showed a germination on an average of 10 per cent below that of seed taken from uninfected branches of MISTLETOE INJURY TO CONIFERS. 31 the same trees. Given the general average percentages of germina- tion of 30 for the former and 40 for the latter, it seems that either from exhaustion of stored materials or tendencies toward abnormal seed production in general the uninfected branch, though suppressed, is still capable of producing a higher quality of seed than the broom. Whether this would be true in the case of young, vigorous brooms is doubtful. Seeds from the uninfected . branches of the same strongly suppressed trees used in the above experiment gave a gen- eral average of 15 per cent below that of seeds taken from vigorous uninfected trees of the same age, species, and habitat. The per- centage of 65 for the uninfected and 40 for the infected shows quite clearly that suppression by mistletoe causes a serious falling off in the quality of the seed of its host. The experiment was conducted in the following manner. Col- lections of cones were made from each of five strongly suppressed and five uninfected trees of all three species. This included one col- lection from the brooms, one from the uninfected branches of each of the suppressed, and one collection from each of the uninfected trees; in all, 45 different collections. One hundred seeds were ex- tracted from each collection and germinated in sand at an average temperature of 35° C. Counts were made at different intervals dur- ing the progress of the test, which was continued for 90 days. Con- siderable difficulty was experienced in procuring the required num- ber of seeds for all conditions, owing to the sterility of the cones on the old brooms. With the increasing age of the broom the seed production falls off, until, as it is with most species, no cones are produced at all. Seeds from recently formed brooms were not tested. It is supposed that they would show a higher percentage of germi- nation. The cones on badly suppressed trees are very often aborted, with shriveled, undeveloped sporophylls, and are frequently infested by cone beetles and cone worms. Seeds, if produced in such cones, are usually below the normal size. A study of microtome sections of the staminate flowers from heavily infected lodgepole pine showed that there was a reduction in the number of pollen mother cells. The staminate flowers when compared with those of normal trees of the same age and condition were found to be uniformly smaller. The sporophylls on the more fertile or convex side of the young pistil- late cones very frequently bore only one ovule (megasporangium), a condition not observed in cones from healthy trees. HOST AFFINITIES IN RELATION TO SILVICULTURE. For practical purposes the following statements on the host re- quirements of the mistletoes of coniferous trees will be found to be of some interest with regard to the silvicultural management of forests. 32 BULLETIN 360, TJ. S. DEPARTMENT OF AGRICULTURE. Razoumofskya douglasii (Engelm.) Kuntze is of economic impor- tance only on the Douglas fir. The affinities of the very small and rare forms of Kazoumofskya on spruce and fir,1 described by Engelmann (6, p. 253) under the name of Arceuthobium douglasii var. micro- carpum for the former host and A. douglasii var. abietinum (3, v. 2, p. 106) for the latter, are not definitely established. In point of time of blooming and seed maturity, it coincides with that of Razoumofskya douglasii for northern regions, and their form and color are quite similar, especially the color of the staminate flowers. These small plants, together with the Douglas fir mistletoe, are the only mem- bers of the genus exhibiting a pronounced color of the lobes, which are a bright, deep purple. Until cross-inoculation experiments are perfected, these particularly small mistletoes on spruce and fir may be considered wholly unimportant from a silvicultural standpoint. For the sake of convenience, they may be placed with the Douglas fir mistletoe and the Avhole designated as the Pseudotsuga-A~bies- Picea group, characterized by their small size and colored flowers. Razoumofskya larids Piper, the most universally distributed and probably the most injurious of the entire genus, is associated with the western larch. This species in a single instance has been col- lected by the writer on lodgepole pine near Missoula, Mont. It is a significant fact that this infection is not vigorous and appears to be dying out. R. americana (Nutt.) Kuntze is more strictly asso- ciated with the lodgepole pine, but is the cause of serious damage to the jack pine (Pinus banksiana) wThere these two species approach each other in Canada. R. tsugensis Rosend., as far as observations in the field have gone, is confined to the hemlocks. The remaining species of importance may be divided into two main groups, a fact that has not been heretofore set forth, viz, those associ- ated with the soft or white pines and those attacking the hard yellow pines. It seems that the members of one group are not in a single in- stance associated with the hosts of the opposite group. The former group includes the following species and hosts : Razoumofskya divari- cata (Engelm.) Coville on the nut or pinon pines, P. edulis and P. monophylla(§, p. 253) ; R. cyanocarpa A. Nels. on P. flexilis (4, p. 146) , P. albicaulis, and P. monticola. Pinus- monticola has not been previ- ously reported as a host for these parasites. Pinus strobiformis, the Mexican white pine, is reported (11, p. 65) as the only host of R. ~blu- meri (A. Xels.) Standley. The second group may be included by the two-form species: R. campylopoda (Engelm.) Piper and R. crypto- poda (Engelm.) Coville. The former is principally injurious to Pinus ponder osa. but is common on P. attenuate (7, p. 366; 13) and P. jeffreyi (10, p. 38). The latter is likewise an injurious parasite on *A1*if8 concolor is also host for Phoradendron 'bolleanum (Seem.) Eichl. (5, p. 193). MISTLETOE INJURY TO CONIFERS. 33 P. ponderosa, but occurs on P. jeffreyi (5, p. 192), P. arizonica (2, p. 243), and P. mayriana (2, p. 243). R. campylapoda has recently been collected by the writer near Coeur d'Alene, Idaho, on P. contorta. Sparingly distributed throughout the Northwest are some large forms of Razoumofskya on Abies, Plants collected by the writer on Abies grandis and A. concolor are apparently the same as that described by Engelmann (3, v. 2, p. 106) on the former host under the name Arceuthobium occidentals var. abietinum. Although it would prob- ably be better on morphological grounds to refer this form to R. campylopoda (Engelm.) Piper, as Engelmann's Arceuthobium occidentale is now named, owing to its seeming close affinity to the genus Abies and the absence of cross-inoculation data it could well be raised to specific rank. These mistletoes in point of mor- phology are in great contrast with the small forms on Abies previ- ously mentioned. They may be considered typical of a group of large forms occurring only on Abies. From the foregoing, it seems possible that the members of the genus Razoumofskya may be arranged in a series of natural groups accord- ing to their host relationships. It is also interesting to note that the largest, the longest lived (both cortical and aerial parts), and the most strictly parasitic forms are associated with the hard or yellow pines. These pines exhibit anatomically a high differentiation. This may throw some light on the nutrient relation of some mistletoes to their hosts ; also their family peculiarities. SUGGESTIONS FOR CONTROL. It is clear from the foregoing pages that the damage to forest growth by the mistletoes of coniferous trees in the Northwest is of sufficient importance to receive the attention of every forester. Steps should be taken in all logging operations, where local problems of economy do not interfere, to make a beginning of the eradication of mistletoe by marking every infected tree for cutting. In some cases it would seem advisable to introduce into the contract a special clause dealing wholly with mistletoe-infected trees. The most injurious of the mistletoes of the genus Razoumofskya on coniferous trees, as indi- cated, are in the main confined to their own particular hosts or to spe- cial groups; hence, it is not advisable to establish in mistletoe regions pure stands of a species much subject to attack. In this respect the problem of the control of mistletoe is similar to that of forest-tree fungi. Mistletoes being light-loving plants, close stands should be maintained as much as possible on all exposed parts of the forest. For the same reason rims of canyons and all exposed areas, such as the borders of bench lands, natural parks, shores of lakes, etc.. should be protected wTith species which are not usually subject to the ravages 34 BULLETIN 360, U. S. DEPARTMENT OF AGRICULTURE. of mistletoes (PL IV, fig. 2) . In this class would fall the firs, spruces, arbor vitses, cedars, junipers, and yews. If this can not be done, owing to certain requirements by these species on soil and climate, the stand should be composed of as many different species as possible. Aside from reasons already set forth, isolated seed trees heavily or even slightly infected by mistletoe should not be retained. The vigor of the parasite on the parent tree will become greater, owing to its response to open and well-lighted conditions. Reproduction under the tree and in its near vicinity, if of the same species, will readily become infected. The same will be true of seed plats. The force developed within the mature seed capsule of these mistletoes and exerted in the expulsion of the seed is a factor of great signifi- cance for the spread of the parasite. It has been demonstrated in the case of one species that this force is sufficient, starting at an elevation of 8 feet on the level, to carry the seed a distance of over 66 feet. In addition to the forcible expulsion of its seeds by the parasite, strong wind is an important factor in seed dissemination. In one instance seeds of the larch mistletoe were collected in number from the roof of a cabin one-fourth of a mile away from the nearest infected tree. This is not at all extraordinary, in view of the fact that the larches of the region are very tall and are heavily infected in the crown. Also strong winds are frequent during the period of seed maturity. Birds and animals play a minor role in the distri- bution of the seeds of these mistletoes.1 In the present instance, however, the seeds adhered to the substratum in the usual and nor- mal manner and could not have been transported in such numbers by any other means than strong wind. In view of the fact that strong air currents are factors in the dis- semination of the seeds, some consideration should be given to the topography and prevailing winds of a region where mistletoe abounds, as influencing the selection of seed plats (if such methods are employed), the placing of strip cuttings, and even of nursery and transplant beds. On a previous page, the tender age at which coniferous seedlings are liable to infection by mistletoe is indicated, so that the above statement regarding nursery sites is not merely a conjecture. Since considerable time elapses between the actual penetration of the primary sinker and the time the infection becomes conspicuous, three years in some instances, it is quite possible for 1 In Bulletin 317 of the U. S. Department of Agriculture, page 24, the writer pub- lished a footnote on the role of birds and animals in the distribution of the seeds of these mistletoes. Since this publication was issued additional observations show that the seeds arc probably more widely distributed by this means than was formerly believed. A rumor has been long extant that grouse feed upon the mistletoes. This has recently been verified by the wrdter by finding in the crop of a grouse the mature seeds and plants of the Douglas fir and larch mistletoes. Mr. Donald Morrison, an old, experienced hunter resid- ing in the mountains near Missoula, states that grouse in the late fall, with the coming of the winter snows, make a practice of congregating in the dense houselike brooms of the Douglas fir mistletoe. Mr. Morrison states quite positively that these birds feed upon the plants and mature seeds of these parasites when other forms of food become scarce. MISTLETOE INJURY TO CONIFERS. 35 young infections on nursery stock to escape detection. Accordingly, young infected seedlings may become a means of distributing and establishing the parasite in plantations generally, not only locally but to far distant regions, when growing stock is shipped either for experimental purposes or for permanent plantings. That this is possible is shown by the discovery in the planting areas near Wal- lace, Idaho (Coeur d'Alene National Forest), of a yellow-pine seedling showing a very recent infection of mistletoe. Since the plantings were made on a widely denuded area and no yellow-pine mistletoe is as yet known to occur in the immediate region, it seems that the seedling must have become infected while at the home nursery at Boulder, Mont., where this mistletoe occurs. In view of the fact that there is a very grave danger of transporting agents injurious to forest growth, either fungous diseases or mistletoe, by sending nursery stock to distant parts of the country, the need of strict sanitation in the neighborhood of forest-tree nurseries can not be overemphasized. Whenever new nursery sites are planned in or near forests, a close pathological survey should be made of the surroundings, and trees diseased or suppressed from any cause what- ever should be cut out. This should be done also where nurseries are already established. The influence of the physical type on the severity of attack should receive considerable attention in any plan of management of forests in mistletoe regions. Forest Assistant Gilkey. in a report on the western larch of the Whitman National Forest, states that " a total of several hundred trees in various parts of the forest shows 79 per cent of the larch to be attacked on the dry-slope type, with only 27 per cent on the more moist sites." The writer's own investigation in the same forest shows an even greater difference between the moist- valley type and the more exposed slopes, which was 87 per cent for the latter and 15 per cent for the former. The severity of the infec- tion on yellow pine and Douglas fir in other regions likewise shows wide extremes as influenced by elevation and exposure. Mr. E. E. Hubert, of the Laboratory of Forest Pathology, reports from ex- tensive observations during a reconnoissance of the lodgepole pine in the Big Hole Valley, Mont., that the most favorable sites for mistletoe are exposed dry ridges and south slopes, where the infec- tion ranges from 50 to 70 per cent of the stand. In the valley type the percentage of infection was much lower. In view of the fact that all economic species so far observed are subject to attack at any age, it is hardly possible to establish an age at which infection becomes so serious as to interfere with the mer- chantability of the host. In regions of heavy mistletoe infection it would be quite impossible, for the reason that there is a much greater chance for all age classes to become infected. In numerous in- 36 BULLETIN 360, U. S. DEPARTMENT OF AGKICULTUEE. stances, however, it is noted that in some regions Douglas fir, larch, and lodgepole pine first become conspicuously infected at sapling or pole size ; that is. it has required several years for earlier infections to become prominent. In any case, the matter turns on the time of life at which a tree becomes infected.- If seriously infected before pole size is reached, the whole tree will in all probability be a cull and a menace to the forest. If infected during or after pole age, the tree may furnish some merchantable material, but will mature far in advance of uninfected trees of the region. Trees infected during early maturity may not be seriously influenced by the parasite ex- cept that their life functions may be slightly changed by brooming and breakage of branches, thus hastening the period of decline. Cutting old and suppressed mistletoe trees is, of course, a saving in several ways, not only to the future forest, but it is getting the best out of a rapidly declining forest capital. Their destruction, how- ever, does not mean that a great advance is being made in eradicating the mistletoe from the region. It simply lessens the chance of infec- tion for a time. Cutting the old and merchantable infected trees and leaving the younger unmerchantable but infected growth will not answer the purpose of control in regions of heavy infection. Very frequently the removal of only the more merchantable mistletoe trees causes the parasite on the trees that are left to develop more vigorously. Numerous observations show that infected trees of various ages succumb very rapidly to the parasite after a certain percentage of the stand has been cut out. For this reason marking the most seriously infected trees for cutting, with the prospect of the least infected reaching a normal maturity or a state of high mer- chantability, should in many regions be discontinued. The only plan left, then, in many regional units of infection is to practice heavier marking than hitherto employed, or, better still, clean cut- ting. It is believed that a close survey of the forests of each district will result in the discovery that there are units or centers of great infection either for one species of mistletoe or for different species. Instances of great regional infection for the Northwest have al- ready been indicated. Strange to say, in some cases these centers of infection are quite sharply defined. It seems entirely possible that if these regions were carefully studied and mapped as to the possible environmental factors governing the vertical and horizontal distribution of the parasite, much practical knowledge would re- sult. If the region should be accessible, the sales policy could be modified, with strong emphasis on the control of the mistletoe, and the knowledge already gained from a detailed study of the region should be available for future forest management. It must be re- membered that the great injury now exhibited by forest growth is the accumulation of many years of unhindered activity by these MISTLETOE INJURY TO CONIFERS. 37 mistletoes. Through a proper appreciation of the need of adopting control measures in all sales areas where the percentage of infection is high and in all replanting projects in mistletoe regions, with the free-use privileges of mistletoed trees and the cutting of all infected growth in the vicinity of forest-improvement stations, a good be- ginning could be made toward the eradication or the lessening of the ravages of these parasites. SUMMARY. The conifers in the Northwest most subject to injury by mistle- toes of the genus Razoumofskya are Larix occidentals, Pinus con- torta, Pseudotsuga taxifolia, and Plum ponderasa. In the order of the above-named hosts the mistletoes most responsible for the greatest damage are Razoumofskya laricis, R. americana, R. doug- lasii, and R. campylopoda. The general nature of the injury by these mistletoes is expressed in a gradual reduction of the leaf surface of the host, which causes a great reduction of growth in height and diameter. New infections take place only through the agency of a germinat- ing seed, which reaches the point of infection through the natural expelling force of the seed capsule, which may be made more effec- tive in point of distance traveled by the aid of strong winds, by falling from branches above after they have been loosened from their original resting place by rains, and by animal life. Trees of all age classes are liable to infection provided the mistle- toe seeds fall on parts of the host not yet protected by the mature cortex. The parasite may spread from the original point of infec- tion into older cortical tissues, which are not liable to infection from without. The spread of the cortical stroma in the reverse direction from the line of growth of the branch may continue until the outer cortex becomes too thick for the aerial shoots to penetrate it. After this, the cortical roots become suppressed and eventually die, or they may become wholly parasitic. Excessive mistletoe infection of the lower branches of a tree may cause the upper portion of the crown to die, giA^ing rise to the phe- nomenon commonly called staghead or spiketop. Severe infection throughout the entire crown often results in the death of the tree. Young seedlings from 3 to 6 years old are often killed within a com- paratively short time after infection. Infection on the branches in practically all cases causes the forma- tion of large brooms, which seriously interfere with the life function of the tree. The same is true in the case of infection on the trunk, whereby burls are formed. The weakening effect of the formation of burls and brooms by mistletoe on forest trees is often responsible for serious depredations by fungi and forest-tree insects. 38 BULLETIN 360, U. S. DEPARTMENT OF AGRICULTURE. In point of quality and quantity the seed-producing capacity of trees suppressed by mistletoe is far below that of normal uninfected trees. Mistletoe can be controlled. It is suggested that a beginning may be made in its eradication or in the reduction of the ravages caused by these parasites by working along the lines indicated in the last section of this bulletin. LITERATURE CITED. (1) ALLEN, E. T. 1902. Western hemlock. U. S. Dept. Agr., Bur. Forestry Bull. 33, 55 p., 5 fig., 13 pi. (2) BLUMEE, J. C. 1910. Mistletoe in the Southwest. In Plant World, v. 13, no. 10, p. 240-246. (3) BREWER, W. H., and WATSON, SERENO. 1876-1880. Botany. [Geological Survey of California.] 2 v. Cam- bridge, Mass. (4) COULTER, J. M. [1909.] New Manual of Botany of the Central Rocky Mountains . . . 646 p. New York. (5) COVILLE, F. V. 1893. Botany of the Death Valley expedition . . . In Contrib. U. S. Nat. Herb., v. 4, 363 p., 21 pi., 1 map. (6) ENGELMANN, GEORGE. 1887. Loranthacese. In Report upon United States Geographical Surveys West of the One-Hundredth Meridian, v. 6, Botany, p. 251-254. (7) JEPSON, W. L. 1901. A Flora of Western Middle California. 625 p. Berkeley, Cal. (8) MACDOUGAL, D. T. 1899. Seed dissemination and distribution of Razoumofskya robusta (Engelm.) Kuntze. In Minn. Bot. Studies, s. 2, pt. 2, p. 169-173, 1 fig., pi. 15-16. MEINECKE, E. P. (9) 1912. Parasitism of Phoradendron juniperinum libocedri Engelm. In Proc. Soc. Amer. Foresters, v. 7, no. 1, p. 35-41, pi. 1-e. (10) 1914. Forest tree diseases common in California and Nevada. 67 p., 24 pi. Washington, D. C. Published by the U. S. Dept. Agr., Forest Service. (11) NELSON, AVEN. 1913. Contributions from the Rocky Mountain Herbarium. XIII. In Bot. Gaz., v. 56, no. 1, p. 63-71. (12) PEARSON, G. A. 1912. The influence of age and condition of the tree upon seed produc- tion in western yellow pine. U. S. Dept. Agr., Forest Serv. Cir. 196, 11 p. (13) PIERCE, G. J. 1905. The dissemination and germination of Arceuthobium occidentale Eng. In Ann. Bot., v. 19, no. 73, p. 99-113, pi. 3-4. ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCUEED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 15 CENTS PER COPY UNITED STATES DEPARTMENT OF AGRICULTURE I BULLETIN No. 490 •flf* Contribution from the Bureau of Plant Industry WM. A. TAYLOR, Chief Washington, D. C. PROFESSIONAL PAPER. January 18, 1917 A PRELIMINARY REPORT ON THE OCCURRENCE OF WESTERN RED-ROT IN PINUS PONDEROSA. By W. H. LONG, Forest Pathologist, Office of Investigations in Forest Pathology. CONTENTS. Introduction Description of western red-rot Development of western red-rot in the tree. . . Comparison of western red-rot and true red- rot Cause of western red-rot . . . Page. 1 1 2 3 3 Entrance of western red-rot into living trees. 4 Summary External signs of western red-rot Areas examined for western red-rot Number and kind of trees examined Western red-rot in black jack and yellow pine. Western red-rot and the rotation for western yellow pine Page. 4 5 5 7 INTRODUCTION. In the national forests of Arizona and New Mexico a varying per- centage of the trees of western yellow7 pine (Finns ponderosa) is affected by an undescribed heart-rot, known locally as red-heart, red- rot, gray-rot, top-rot, and heart-rot. The amount of this rot present varies materially with the exposure, slope, and soil on which the yellow pine is growing, as well as with the age of the timber itself. It is the main heart-rot found in western yellow pine in Arizona and New Mexico and causes an annual loss of thousands of dollars. This heart-rot is here called " western red-rot " in order to dis- tinguish it from the true red-heart or red-rot, a very similar heart- rot common in many species of conifers throughout the world. True red-rot or ring scale is caused by Trametes pini, while western red-rot is produced by an entirely different fungus. DESCRIPTION OF WESTERN RED-ROT. CROSS-SECTIONAL VIEW. Western red-rot may show in the end of a freshly cut log any one of the following stages: (1) An early stage, in which the heartwood is firm but shows reddish to dark-brown discolored areas. Such 64936°— 17 2 BULLETIN 490, U. S. DEPARTMENT OF AGRICULTURE. areas are often fan shaped and radiate outward from the center of the log, like spokes from the hub of a wagon wheel, or they may he isolated and occur anywhere in the heartwood. (2) A more ad- vanced, or what might be called an intermediate stage, of the rot, in which the affected heartwood is whitish or grayish in color and is so disintegrated that small pieces can be pulled out. The rotted wood consists of soft white strands of cellulose, intermixed with less rotted wood particles. The rotten wood in this stage is often so wret and soggy that water can be squeezed out of it. The white-rot or gray- rot stage is usually in the center of the log and is often surrounded by the brownish fanlike areas seen in the first stage of the rot. (3) A third or final stage of the rot, in which much of the heartwood has been destroyed, leaving the remainder in a very brittle, rotten condition, so that it easily crumbles when handled. In this final stage of the rot all of the cellulose has been absorbed by the fungus, while the wood particles left are reddish to dark brown in color. This stage sometimes occupies only a small portion of the heartwood in the center of the log and may be surrounded by one or both of the other stages. LONGITUDINAL-SECTION VIEW. In a longitudinal section, as seen in sawed lumber, the different stages of the rot gradually merge into one another. In the place where the fungus entered the tree will be found the oldest stage which the rot has reached in that particular lesion. If the entire lesion originated from only one center of infection (one dead branch) and the rot has been in the tree for many years, then the three stages described will probably be represented in the one lesion, which may be anywhere from 12 to 20 feet long. There will usually be some 6 to 10 feet in the center of the log which belong to the second and third stages of the rot. while the extremities of the rot lesion will consist of the first stage of the rot. DEVELOPMENT OF WESTERN RED-ROT IN THE TREE. This rot advances nearly as rapidly radially as it does longitu- dinally in the heartwood of the affected tree. Its radial development in the wood is rather peculiar. From the central cylinder of the rot, at irregular intervals along its entire length, narrow radial patches of rot extend outward toward the sapwood. These radial patches are the fanlike or spokelike discolored areas on the end of the log. described under the first stage of the rot. The centers of these radial patches usually consist of whitish delignified tissue, bordered by red- dish to dark-brown areas of heartwood which have not yet been de- lignifiecl but are in the early stages of the rot. Often some of the cellulose in the center of these patches has been entirely absorbed, leaving small irregular cavities extending to the sapwood. WESTERN RED-ROT IN PINUS PONDEROSA. 3 From these radial patches the rot spreads in all directions, until finally the entire heartwood is involved. In tangential sections these radial patches of rot appear as irregular elliptical reddish to brown areas with white centers. These areas are two to several times longer than broad, with their greatest diameter lying parallel with the grain of the wood. There is often a small cavity bordered by the unabsorbed remnants of the delignified tissue in the center of each rotted area. Usually two to six of these discolored areas are grouped together, giving the sawed lumber a very peculiar appear- ance. COMPARISON OF WESTERN RED-ROT AND TRUE RED-ROT. When examining the rot in the end of a freshly cut pine log it is often difficult to determine whether it is western red- rot or true red-rot. A longitudinal view of the rot, however, usually will settle the question beyond any reasonable doubt, since the following con- stant characters are then in evidence: (1) True red-rot, or red-heart, caused by Trametes pini, has many small but sharply defined pockets, or cavities, in the heartwood, lying parallel to the grain of the wood, while western red-rot never has these typical pockets. (2) The attacked wood in true red-rot is usually very firm, even in the final stage of the rot, while western red-rot in its last stage is much dis- integrated and easily crumbles when handled. (3) The mycelium of true red-rot when growing in heartwood which is more or less exposed to the air is brown, while the mycelium of the western red- rot is always white. (4) The attacked heartwood in true red-rot never becomes wet and soggy, as it often does in certain stages of western red-rot. CAUSE OF WESTERN RED-ROT. The fungus which causes western red-rot never forms brown, woody, perennial fruiting bodies on the boles of living affected pine trees, as Trametes pini does, but forms annual fruiting bodies, which are usually developed as white encrusting layers on the under side of logs lying on the ground. This fungus is also the main agent in rotting the sapwood of the cull logs and large branches of the yellow- pine slash.1 The fruiting bodies, or sporophores, of this fungus, as they occur in Arizona and New Mexico, are usually resupinate, with a hymenial layer consisting of minute tubes or pores. However, fruiting bodies have been found which have distinct and well-formed pilei. The pileate form of the fungus resembles very closely Polyporus ellisianus (Tyromyces ellisianus of Murrill in North American Flora) ; the 1 Long, W. II. A new aspect of brush disposal in Arizona and Xe\v Mexico. In Proc. Soc. Amer. Foresters, v. 10, no. 4, p. 383-398. 1915. 4 BULLETIN 490, U. S. DEPARTMENT OF AGRICULTURE. writer, however, does not wish to call it by this name until the in- vestigations now under way as to its identity are completed. Lloyd reports a specimen of the same fungus from the State of Washington, collected by J. M. Grant,1 and refers it to Polyporus ellisianus. The writer (through the kindness of Mr. Lloyd) has been able to examine a portion of the collection from Washington, and it agrees in all essential characters with the fungus which causes west- ern red-rot in Arizona and New Mexico, Concerning the host of the Washington specimen Lloyd writes, " There was no note with the specimen regarding its host, excepting that it grew on a pine of some kind." A sporophore of what is apparently the western red-rot fungus has been examined from Idaho. Von Schrenk2 in 1903 published a figure of a heart-rot of living trees of Pinus ponderosa from the Black Hills Forest Reserve in South Dakota, which is typical of the second stage (cross-sectional view) of this rot as it occurs in yellow pine in New Mexico and Arizona. It is therefore highly probable that this fungus is widely distributed throughout the West, both as a saprophyte in slash and dead trees and as a heart-rot in living timber. The writer has examined a speci- men of the same fungus collected in New Jersey on Pinus sp. and one of both fungus and rot from Vermont on P. strobus. ENTRANCE OF WESTERN RED-ROT INTO LIVING TREES. The western red-rot fungus enters the living tree through dead branches in the crown. It first attacks the sapwood of the dead branch ; then the heartwood. It then travels down the sapwood and heartwood of the dead branch into the heartwood of the living tree. Once established in the tree, the fungus apparently continues to grow as long as the tree is alive, spreading in all directions, until often the heartwood of the entire bole of the tree, as well as that of the large branches, is invaded and rendered worthless for lumber. EXTERNAL SIGNS OF WESTERN RED-ROT. No external signs were found which would absolutely determine whether or not a given standing yellow-pine tree was defective. Trees having large dead branches intermixed with living limbs and ragged and unhealthy looking crowns were often attacked by western red-rot. Such defective trees were usually located on very thin soil on steep south or east slopes, where growth conditions were very poor. However, many trees which showed no recognizable external evi- dences of decay were found to have western red-rot when they were felled. 1 Lloyd, C. G. Mycological writings, v. 4, letter no. 60, p. 4. 1915. - Schrenk, Hermann von. The " bluing " and the " red rot " of the western yellow pine, with special reference to the Black Hills forest reserve. U. S. Dept. Agr., Bur. Plant Indus. Bui. 36, p. 34, 40, pi. 14, fig. 2. 1903. WESTERN RED-ROT IN PINUS PONDEROSA. 5 AREAS EXAMINED FOR WESTERN RED-ROT. Before marking an area for cutting it should be determined whether the rotation is to be short, medium, or long. Often the amount and character of the defect present in the timber will be an important factor in determining what rotation is best for the area in question, especially in stands of virgin timber. In order to throw some light on the presence of defects, especially western red-rot, in western yellow pine and its probable influence on the rotation period, studies were conducted on certain areas in the Santa Fe National Forest where both tie trees and saw timber were being cut. The main problem which demanded immediate attention was the relative amount of rot present in the black jack on these areas compared to that in the yellow pine. The special areas examined were located in Cienega, Ocho, Amole, Gallegos, and La Junta Canyons and on adjacent mesas, all of which are situated in the Cienega ranger district. The data given here were obtained mainly from Cienega, Ocho, and Amole Canyons on areas which had been cut for hewn ties. A small area near the Cienega ranger station on which both ties and saw timber had been cut was also examined for rot. The tie trees ranged from 10 to 16 inches, d. b. h., while those over these diameters were saw timber. These areas were especially suitable for a study of this character, since an unusually large per- centage of the black jack (30 to 50 per cent) and nearly all of the yellow pine (85 to 100 per cent) were being cut. There are two forms of western yellow pine called, respectively, black jack and yellow pine. Black jack is the form which this pine assumes before it reaches the age of 125 to 150 years.1 During this period its bark is blackish to dark brown, with narrow furrows, while the yellow-pine form has lighter colored, widely furrowed bark. NUMBER AND KIND OF TREES EXAMINED. In the vicinity of the Cienega ranger station, 1,691 felled black jacks and 547 felled yellow-pine trees were examined for rot. In addition to this, all of the trees 4 inches, d. b. h., and over on a sample strip 1 chain wide and 140 chains long, located on the mesa between Ocho and Cienega Canyons, were tallied by the district marking board of the Forest Service, carefully examined, and any evidences of disease or defect noted. One hundred and twenty- four felled black jacks (10 to 16 inches, d. b. h.) and 16 felled yellow pines (12 to 16 inches, d. b. h.) had been cut for hewn ties on this sample strip. Table I shows the number of sound and defective trees on each of the areas examined and in a general way the character of the 1 Woolsey, T. S., jr. Western yellow pine in Arizona and New Mexico. U. S. Dept. Agr., Forest Serv. Bui. 101, 64 p., illus, 4 pi. 1911. BULLETIN 490, U. S. DEPARTMENT OF AGEICULTURE. site on which the trees were located. The amount of butt-rot (prob- ably caused by Polyporus schweinitzii) present on the areas ex- amined was so small that it was not included in the table. This ex- plains any apparent discrepancy between the sum of the sound and defective trees and the total number of trees listed in the table. TABLE I. — Data on sound and defective felled trees of black jack and yellow pine. Area. Kind of timber. Num- ber of trees. Sound trees. Defective trees (western red- rot). Remarks. Num- ber. • Per cent. Num- ber. Per cent. 2 3 4 5 6 1-6 /Blackjack \Yellow pine 210 20 294 84 126 132 206 76 855 235 124 16 206 18 293 73 124 87 193 57 836 223 123 13 98 90 99.66 86.9 98.4 65.9 93.7 75 97.7 94.9 99.2 81.25 4 2 0 10 2 40 9 14 14 -8 0 3 1.9 10 \Top of ridge; growth conditions fair. / mainly black jack. Lower portion of southeast slopes and bed of canyon; growth con- ditions fair. South and southeast slopes; thin • soil; slopes steep, rocky; growth conditions poor. South and east slopes; thin soil; • slopes steep; growth conditions ( poor. \ Mesas; soil good; growth conditions / good. H4-acre sample strip across mesa; / growth conditions fair. iTotal for all areas. /Blackjack \Yellowpine /Blackjack 11.9 1.6 30.3 4.3 18.4 1.6 3.4 \Yellowpine /Blackjack \Yellow pine /Blackjack \Yellow pine /Blackjack \Yellow pine . . 18.75 f Black jack. . 1,815 563 1,775 471 97.8 83.6 29 77 1.59 13.6 I Yellow pine I Both kinds .... 2,378 2,246 94. 4 106 4.5 DISCUSSION OF THE DATA PRESENTED IN TABLE I. A study of Table I shows several interesting facts : ( 1 ) There is a marked difference in the percentage of black jack and of yellow pine affected by western red-rot. (2) The site seems to have a decided influence on the occurrence of this rot, especially in the yellow pine. (3) The variation in the percentage of western red-rot on the dif- ferent areas shown in the table is due to several factors, the three most prominent ones being the relative proportion of black jack and yellow pine which had been cut on each area, the influence of the site on the growth of the trees, and the age of the timber. For instance, on area No. 3 the percentage of this rot in yellow pine is high, due apparently to unfavorable growth conditions and the age of the timber cut. Table I should give a fairly accurate idea of the occurrence of west- ern red-rot in black jack of merchantable size in this region, since 1,855 trees of this kind were examined over areas where 30 to 50 per cent of the black jack 11 inches, d. b. h., and over had been cut. As an indication of the amount of this rot present in the yellowT pine, Table I is not so conclusive, since, with the exception of areas 3 and 4, all of the yellow pine shown in the table was of small diameter (12 to 18 inches, d. b. h.) and was cut for hewn ties only. This means that the percentage of trees showing western red-rot in the yellow pine on these areas will be greater than is shown in the table, except WESTERN RED-ROT IN PINUS PONDEROSA. 7 areas 3 and 4. The older the trees are, the greater the amount of rot present, since such trees have had more opportunities for infection than younger trees. However, taking the area as a whole, probably •20 per cent of the yellow-pine trees (exclusive of black jacks) will show western red-rot in some portion of the bole. The areas shown in this table are mainly covered with black jacks intermixed with only a small number of yellow pines. For instance, in the sample strip, 1 chain wide and 140 chains long, 195 black jacks were marked for cut- ting and 1,270 left, a total of 1,465 black jacks 4 inches, d. b. h., and over, while 108 yellow pines were marked and 22 left. Of the 1,465 black jacks present on this area, there were 605 trees of merchantable size (10 inches, d. b. h., and over) to only 130 yellow pines. This means that on such areas the percentage of western red-rot in the mer- chantable timber will be small compared to similar areas where the proportion of yellow pine is greater than that of black jack. WESTERN RED-ROT IN BLACK JACK AND YELLOW PINE. The percentage of western red-rot in black jack for all the areas is very small, since only 29 trees out of 1,815 (1.59 per cent) showed this rot, while in yellow pine it was much greater, 77 trees out of 563 (13.6 per cent) being infected. Even then, this percentage is not high when compared with some other areas in Arizona and New Mexico. For instance, on certain sale areas on the Upper Pecos Kiver, 70 to 95 per cent of the yellow-pine trees were attacked by western red-rot. Since this rot enters mainly through dead branches it is easily seen why fewer black jacks are attacked by it than yellow pines. The total percentage of trees attacked by western red-rot, both black jack and yellow pine, is only 4.5 per cent for all the areas shown in Table I. Of the black jacks infected with western red-rot, nearly all were suppressed or grown under very unfavorable conditions. This indi- cates that all such trees should be marked for cutting when possible, not only on account of their susceptibility to this rot, but also be- cause they will never make strong, thrifty trees. When the soil is deep and capable of producing vigorous growth in the trees, western red-rot is present only in a small degree unless the trees are very old and overmature. Such soil conditions are found on many of the mesas and near the bottoms of small canyons. There is always a marked increase in the amount of western red-rot in yellow pine growing on very steep slopes and on poor, thin soil. WESTERN RED-ROT AND THE ROTATION FOR WESTERN YELLOW PINE. As to the relative efficiency of a long rotation and of a medium or short rotation period in finally eliminating this rot from the forest, the answer is very evident, judging from the viewpoint of the rot 8 BULLETIN 490, U. S. DEPARTMENT OF AGRICULTURE. alone. Table I clearly shows that during the black-jack period the trees are practically free from this rot, but as they grow older the increasing number of dead branches makes them more open to the attacks of this fungus ; that is, after the trees enter the yellow -pine stage of their growth they are more and more subject to infection by heart-rotting fungi. In the Cienega ranger district western yellow-pine trees up to 125 or 150 years old (the black-jack period) are rarely attacked by western red-rot, for the reasons previously given, while trees over 200 years old show a much higher percentage of rot than the younger trees (black jack). Any system of cutting that will take out most of the older trees (yellow pine) and many of the larger black jacks, as well as all suppressed trees, will do much to rid the future forest of this serious heart-rot. It also follows that a short rotation will be better for the future health of the forest so far as heart-rots are concerned. It is a fundamental fact that the older a tree is, the more liable it is to be attacked by heart-rotting fungi. SUMMARY. (1) A varying percentage of western yellow pines in Arizona and New Mexico is affected by a serious heart-rot called in this bulletin western t red -rot. (2) Western red-rot has three stages in its development: (a) An initial stage, in which the affected heartwood is firm but shows red- dish to dark-brown discolored areas; (b) an intermediate stage, in which the diseased heartwood is whitish or gray in color and more or less delignified; (c) a final stage, in which much of the heartwood has disappeared, owing to the absorption of the delignified por- tions, while the wood particles left are brittle and crumble easily when handled. (3) Western red-rot attacks both the sap wood and the heartwood of dead branches on living trees. It then travels down the dead branches into the heartwood of the living tree. (4) No constant external signs were found which would abso- lutely determine whether or not a given living yellow-pine tree was attacked by western red-rot. However, trees growing on very thin soil on steep south or east slopes where growth conditions are very poor have a higher percentage of this rot than yellow pines situated where the growth conditions are good. (5) Of the 1,815 black jacks examined for western red-rot, only 29, or 1.59 per cent, had this rot, while out of 563 yellow pines ex- amined, 77, or 13.6 per cent, were attacked by this rot. (6) So far as heart-rots are concerned a short rotation is better for the future health of the forest than a long one. WASHINGTON : GOVERNMENT PRINTING OFFICE : 1917 BULLETIN OF Contribution from the Bureau of Plant Industry, Wm. A. Taylor, Chief. June 24, 1914. " (PROFESSIONAL PAPER.) NEW FACTS CONCERNING THE WHITE-PINE BLISTER RUST.1 By PERLEY SPAULDING, Pathological Inspector, Federal Horticultural Board (formerly Pathologist, Office of Investigations in Forest Pathology}. INTRODUCTION. In a recent publication2 the writer gave the latest information regarding the white-pine blister rust up to the spring of 1913. The past season has brought forth several additional developments, which are of great importance. THE SITUATION AT GENEVA. Since 1906, when Stewart first discovered the presence of Cronar- tium ribicola upon Ribes at Geneva, N. Y., the disease has been found there in several different years.3 This occurred in spite of the total destruction of the Eibes found affected in 1906 and the apparent absence of the secial stage of the fungus on the neighboring white pines.3 In the spring of 1913 the New York State department of agriculture took up the matter, and a special effort was made to locate and examine every white-pine tree within the diseased area, with the result that two trees about 15 years old were found by Inspector Maney bearing the fruiting bodies of the fungus. They were promptly destroyed. These evidently had been diseased for a long time, probably since they were 3 or 4 years old. No definite i This paper is intended to supplement the previous publication, Bureau of Plant Industry Bulletin 206, entitled "The Blister Rust of White Pine." It is, therefore, as brief as possible, and care has been taken not to duplicate statements made in that publication. These two bulletins are necessary in order to secure complete information regarding this disease. a Spaulding, Perley. The present status of the white-pine blister rust. In U. S. Dept. Agr., Bur. Plant Indus. Circ. 129, p. 9-20, 6 fig. 1913. 3 Stewart, F. C. Pine blister rust and currant felt rust. In West. N. Y. Hort. Soc. Proc. 58th Ann. Meeting, p. 122-124. 1912. Stewart, F. C., and .Rankin, W. H. Can Cronartium ribicola overwinter on the currant? In Phyto- pathology, v. 4, no. 1, p. 43. 1914. Jordan, W. H. Director's report for 1906. N. Y. State Agr. Exp. Sta. Bui. 284, p. 341-342. 1906. Director's report for 1912. N. Y. State Agr. Exp. Sta. Bui. 356, p. 559. 1912. NOTE.— This paper contains additional information concerning the white-pine blister rust that was collected during the season of 1913. It is of interest to foresters, tree experts, nurserymen, and owners of ornamental and forest plantations of 5-leaved pines. 45612°— Bull. 116—14 2 BULLETIN 116, U. S. DEPARTMENT OF AGRICULTURE. information concerning their origin could be obtained, but it is believed that they were imported when 3 or 4 years old, that the disease came with them, and that they have been serving ever since as a center of infection each season for the Kibes in that vicinity. During the season of 1913 the disease appeared on but few Eibes bushes near the two trees above mentioned. The pines of the vicinity are to be held in quarantine and inspected each spring. In spite of the recent pessimistic opinion of those most directly concerned in the mat- ter,1 there is every reason to believe that the disease will soon be eradi- cated at this point, now that the Center of infection is finally located. The conclusion that " complete eradication of the disease is no longer possible" is apparently meant to apply to the entire country and is based on the fact that blister rust was established at Geneva and the supposition that it was established in other places in New York, Mas- sachusetts, and Connecticut. Now that the disease is well in hand in the Geneva area (the most dangerous one known at that time in the entire country2) , there seems to be no sufficient reason for giving up the fight against as dangerous a disease as this promises to become if unchecked. This is especially true in view of earlier statements as to the seriousness of this disease.3 NEW OUTBREAKS. Early in July the writer received specimens of white pine affected with blister rust from a point in northern Vermont which had not been previously known as harboring the disease. Inquiry showed that it was present upon native trees in that vicinity, this being the first known instance in this country. A visit was immediately made to determine the facts in the case, and the disease was found in the ornamental plantings of a large private estate. The original source of infection is unknown. It is quite possible that a few imported white-pine trees were obtained years ago, although it is definitely known that most of the trees in the vicinity are native and grew in the near-by woods. At any rate, the disease has been in some of the trees about 10 years, judging from the location of the cankers and their general appearance. Of the total number of white-pine trees In that vicinity, about 150 in all, more than 50 were found to be visibly affected by the disease. How many may later develop blister rust is, of course, unknown, but probably 5 or 10 per cent will do so. Already about 33 J per cent have it, which should be sufficient to con- vince the occasional skeptic that this will be a serious disease 4 if allowed to run its course in this country. 1 Stewart, F. C., and Rankin, W. II. Cronartium ribicola and the proscription of Ribes nigrum. (Ab* stract.) In Phytopathology, v. 3, no. 1, p. 73. 1913. 2 Stewart, F. C., loc. cit. 3 Stewart, F. C., loc. cit.; Jordan, W. H., loc. cit., 1912. < Clinton, G. P. Notes on plant diseases of Connecticut. In Conn. Agr. Exp. Sta. Rpt., 1909-10, p. 733. 1911. WHITE-PINE BLISTER RUST. 3 The disease had evidently reached a sfrage at this place where its future spread would be much more rapid than it has been in the past. About lOOfeetfrom the apparent original center of infection was a single black-currant bush (Ribes nigrum),1 some 50 to 75 red-currant bushes (Ribes vulgare), and about 30 gooseberry bushes (Ribes grossularia) . The leaves of the black currant were covered with telia and uredinia of Cronartium ribicola, but only a very few sori were found on the red currants and none on the gooseberry leaves. Evidently the conditions have been extremely favorable for the propagation and spread of the fungus ever since the Ribes were set in that locality. Ah* of the Ribes have been removed and destroyed, and the diseased trees and parts of trees are being cut out and destroyed. Late in the fah1 of 1912 the writer received a specimen of blister rust on leaves of Ribes from Ipswich, Mass. In the spring of 1913 two small white pines which bore fruiting bodies of the fungus were found by the State nursery inspector near the diseased Ribes bushes. These were destroyed, and it was believed that the disease had been eradicated. It appeared later, however, about half a mile away, on leaves of Ribes nigrum and of Ribes vulgare of the variety Red Cross. The abundance of the fungus led the writer to suspect the center of infection to be near by. An examination promptly revealed evidences of the disease on neighboring white pines of about 10 and 18 years of age. Steps are being taken to remove the diseased trees and branches and also the black currants. In 1913 Clinton 2 reported an outbreak of this fungus on the leaves of black currants near Meriden, Conn., late in 1912. He examined the vicinity, but could find no infected white pines in that locality. The origin of this outbreak is still unknown, and for this reason the situation is perhaps more dangerous than that in any other locality where the disease is now known to occur. SERIOUSNESS OF THE DISEASE. In the Vermont locality mentioned one large white pine about 2 feet in diameter and quite mature from the lumberman's standpoint was found to have the disease scattered throughout the top. Branches of all sizes up to 4 inches in diameter were thus affected. From the condition of this tree it was very easy to understand how a large tree may be killed by very severe attacks of this fungus, since it is a mere matter of time before an attacked branch or tree trunk is killed above the point of infection. One tree about 20 years of age, which had been infected in the trunk about 10 feet from the ground, 1 The three Ribes mentioned are cultivated species which have been introduced into this country from Europe. The last (Ribes grossularia) is usually placed in a different subgenus than are the two first; by some authors it is placed in a separate genus. 2 Clinton, G. P. Notes on plant diseases of Connecticut. In Conn. Agr. Exp. Sta. Rpt., 1912, p. 347-348. 1913. 4 BULLETIN 116, U. S. DEPARTMENT OF AGRICULTURE. had its top entirely dead above that point. Numerous small branches were found on other trees in a similar condition. A number of other trees of the same age apparently have been killed in a similar way, as they have been dying for years and have had to be removed, one or two at a time. While it takes a long time for the destructiveness of this disease to reach its climax in any given locality, there can be no doubt that if it finally becomes established and generally distributed in our forests it will be the worst enemy the white pine has here, as is stated to be the case in certain European countries.1 It has become so thoroughly established in Europe that there is no hope of eradi- cating it there, but there is yet time to suppress it here if the danger is once generally realized. Even with conditions as they are in Europe, one of the most prominent plant pathologists of Germany recom- mends the energetic fighting of this disease.2 If such action is advisable in Europe, even more drastic action is certainly proper in this country. CAN THIS DISEASE WINTER t>VER ON RIBES? Late in 1912 F. C. Stewart asked the writer to take part in a cooperative experiment to try to determine whether this disease can winter over on dormant Kibes stock and thus be carried from one place to another in stock which has previously been diseased. Two hundred 2-year-old Eibes nigrum plants which had been heavily rusted by Oronartium ribicola in the late summer and early fall of 1912 were sent to the writer at Washington, D. C., about December 1. They were promptly heeled in out of doors until February 1, when, according to agreement, they were potted and brought into the greenhouse. They started quickly and made a very vigorous growth. They were examined several times for the presence of Cronartium ribicola, but none was found. The experiment was concluded about May 20 because of the writer's absence after that date. Parallel tests were made at Geneva and Ithaca, N. Y., Lafayette, Ind., Amherst, Mass., and New Haven, Conn., 300 plants being used.3 The results were entirely negative. The evidence furnished by the 1 Bos, J. Ritzema. Phytopathologisch laboratorium "\Yiilie Commelin Scholten. Verslag over de inlich- tingen gegeven in 1900. In Landbouwk. Tijdschr., jaar 9, p. 77. 1901. Fisher, W. R. Experimental plantations at Coopers Hill. In Quart. Jour. Forest., v. 3, no. 3, p. 229. 1909. Fron, Georges. Nouvelles observations sur quelques maladies des jeunes plants de Coniferes. In Bui. Soc. Mycol. France, t. 27, no. 4, p. 476-481. 1911. Lind, Jens. Danish fungi as represented in the herbarium of E. Rostrup, p. 281-283. Copenhagen, 1913 Neger, F. W. Die Nadelholzer ... p. 110-111. Leipzig, 1907. Somerville, W. Peridermium strobi, the blister of Weymouth pine. In Quart. Jour. Forest. , v. 3, no. 3, p. 232-236. 1909. Watson, J. G. The Woburn forests. In Gard. Chron., s. 3, v. 52, p. 422. 1912. 2 Tubeuf, Carl von. tJber die Verbreitung von Baumkrankheiten beim Pflanzenhandel. In Mitt. Deut. Dendrol. Gesell., p. 156-163, 1904. 3 Stewart, F. C., and Rankin, W. H. Can Cronartium ribicola overwinter on the currant? In Phyto- pathology, v. 4, no. 1, p. 43. 1914. WHITE-PINE BLISTER RUST. 5 natural occurrence of the disease shows that dormant Ribes stock docs not harbor the fungus. But all the evidence is negative (except that mentioned earlier by the writer) 1 and is subject to certain limitations, as is all negative evidence, when general conclusions are drawn from it. That is, it does not effectually dispose of possible rare exceptions, which may occur only once in thousands of cases. The practical conclusion is that Ribes plants do not carry the fungus over winter and that an outbreak of this disease on Ribes is to be attributed to the presence of neighboring white pines which have the blister rust. Hence, wThen the disease is found on Ribes leaves a special effort should be made to locate and destroy infected trees.2 Ewert 3 has recently published a paper showing that thorough spray- ing with Bordeaux mixture, with special care to cover the lower surface of the leaves, will almost completely control this fungus upon Ribes nigrum. It is suggested that in the future when diseased pine trees are found early in the summer, any Ribes in the vicinity be promptly sprayed on both sides of the leaves, in order to reduce the resulting infections and the outbreak of the uredo stage. Spraying should not be resorted to except as a temporary expedient, as just indicated. About May 15, 1913, several plants of Ribes nigrum were isolated and an attempt was made to inoculate them with telial material furnished by Stewart which had been kept out of doors all winter. This attempt was unsuccessful, as was also a similar one made by the writer in 1912 with fresh teliospores. CULTIVATED VERSUS WILD RIBES. A statement has been made implying that the cultivated species of Ribes are not dangerous factors in connection with this disease.4 All of our experience in this country shows that the contrary is true. In no known case has the disease been discovered on native wild species of Ribes, while it has been found in a number of cases on the cultivated species of Ribes nigrum and Ribes vulgare. The evidence shows that our native wild Ribes cynosbati and Ribes prostratum are resistant to the fungus, while Ribes nigrum is exceedingly susceptible, and some varieties of Ribes vulgare are quite susceptible. The variety Red Cross has been found in one instance to be seriously diseased. Ribes grossularia has been immune. The cultivated Ribes are much 1 Spaulding, Perley. Notes upon Cronartium ribicola. In Science, n. s., v. 35, no. 891, p. 146-147. 1912, The present status of the white-pine blister rust. In U. S. Dept. Agr., Bur. Plant Indus. Circ. 129, p. 17. 1913. 2 Spaulding, Perley. Notes on the white-pine blister rust. (Abstract.) In Phytopathology, v. 4, no. 1, p. 41^2. 1914. 3 Ewert, R. Erfolgreiche Bekampfung des Cronartium-Rostes auf der schwarzen Johannisbeere. In* Ztschr. Pflanzenkrank., Bd. 23, Heft 8, p. 463-47-6, 2 fig. 1913. < Clinton, G. P. Notes on plant diseases of Connecticut. In Conn. Agr. Exp. Sta. Rpt., 1909-10, p. 732 1911. 6 BULLETIN 116, U. S. DEPARTMENT OF AGRICULTURE. more dangerous than are the native wild plants, because many white- pine plantations are made on deserted farms. In such places the former garden currants persist for years, and the inspector often finds them in the midst of a plantation of imported pines. Moreover, nurserymen often keep stocks of white pines and Ribes in proximity to each other, which is dangerous if either has the disease. These facts do not mean that wild species of Ribes can be disregarded, but that both wild and cultivated species must be considered when con- trol measures are undertaken. PINUS EXCELSA A HOST. In a recent publication Lind1 mentions the Himalayan, pine (Pinus excelsa) as a known host of the white-pine blister rust in Denmark. The writer is informed that the disease was found in 1913 upon young trees of Pinus excelsa in Massachusetts. Unfortunately, no specimens of it were saved, but there seems to be no doubt that Pinus excelsa is a host of this fungus and is liable to be affected by it in this country. This is the first time that the white-pine blister rust has been found here on any other species of pine than Pinus strobus. AGE OF DISEASED WHITE-PINE TREES. White-pine trees from 3 to about 75 years old having the blister rust have been seen. From 3 to 15 years the series was almost unin- terrupted; then the ages were approximately 18, 20, 25, and 75 years. The trees of 25 and 75 years were diseased on the branches and not on the main stem, but below 25 nearly all have been affected on the main stem. The evidence seems to show that this disease has been present on small numbers of imported pine trees in this country since 1888, and perhaps longer.2 DISTRIBUTION OF SPORES OF CRONARTIUM RIBICOLA. In 1912 the writer made some observations on the distribution of the spores of Cronartium comptoniae from Pinus rigida to Comptonia asplenfolia* The seciospores are so similar in size and shape to those of the blister rust on white pine that it seems probable that one would be distributed as far as the other under the same conditions. It was found that the seciospores of Cronartium comptoniae were blown about 30 feet from their point of origin. This led the writer to sus- pect that the seciospores of the white-pine blister rust would also be blown relatively short distances. Such has been the case in all those lLind, Jens. Danish fungi as represented in the herbarium of E. Rostrup, p. 281-283. Copenhagen, 1913. 2Spaulding, Perley. The blister rust of white pine. U. S. Dept. Agr., Bur. Plant Indus. Bui. 208, p. 36. 1911. 8 Spaulding, Perley. Notes on Cronartium comptoniae. In Phytopathology, v. 3, no. 1, p. 62. 1913. WHITE-PINE BLISTER RUST. 7 not so much in the total number of diseased trees present as it does instances that the writer has had an opportunity to investigate per- sonally and where the origin of the spores has been determined. Two instances, on the other hand, where no diseased pines were found, seem to indicate that the seciospores were blown long distances, though this is by no means a certainty. In the three instances exam- ined by the writer in 1913, the Ribes were about 100 feet from the diseased pines. There is every reason to believe that the uredo- spores of the white-pine blister rust may be blown half a mile or more.1 GENERAL RESULTS OF INSPECTIONS. Some of the general results of the annual inspections made for the white-pine blister rust, beginning in 1909 and continued to the pres- ent time, are of interest. In the States north and east of Washington, D. C., about 4,000,000 white pines are known to have been imported since 1900. Probably 500,000 more have been privately imported, about which nothing is known, making a total of about 4,500,000 trees imported into these States. Of this number 1,725,000 are known to have been destroyed before they reached the hands of pri- vate individuals, leaving 2,775,000 which have been set out in lots ranging from 500 to several hundred thousand trees. The number of such known lots is approximately 200. The inspection of these trees has varied much, some having been inspected once, some care- fully inspected for the first time in 1913, and still others carefully inspected each year since the discovery of the disease on pines in this country in 1909. The figures given in Table I cover only those plantations that have been continuously under inspection from the beginning. TABLE I. — Results of the continuous inspection of infected lots of white-pine trees. No. Item. Number. 1 Total trees inspected 910, 000 2 Total trees found diseased 8,177 3 4 Total trees found with fruiting bodies of the fungus (data available for but 560,000 trees). Lots of trees inspected 938 150 ore bodies may be, nobody knows. They occur in a considerable number of closely related parasites, but are not known to reproduce the disease in any way. They are simply indicators of the disease. They are known as pycnospore-s. Shortly after the pycnospores are produced, from the latter part of April until about the middle of June, the real fruiting bodies push their way through the swollen tissues of the bark until they become visible on the exterior. Here, they first appear like white blisters as large as a child's finger nail. After a brief time, the top of the white membrane breaks loose and falls off. Then it is seen that this membrane surrounds a mass of bright-yellow powder (fig. 1 and PL I, A). Each grain of this powder is a spore, capable of repro- ducing the disease. These spores can not, however, infect the pines, but can only attack leaves of currants or gooseberries. After the parasite has fruited once upon the pine, the latter may remain alive until the next year (fig. 1). In most cases, however, the bark is killed completely around the affected part, thus girdling it (figs. 1 and 2) . In most cases this means the immediate death of the outer or upper portion of the branch or trunk. Some trees, however, struggle along for a number of years, and sometimes even for 15 or 20 years. In such cases the parasite sends out a new crop of spores each spring to infect any currants or gooseberries that may be in the vicinity. These yellow spores produced in the blisters in the pine bark are known as aeciospores, or Peridermium spores. The Peridermium spores above described are very easily blown about by the wind, and undoubtedly they are distributed mostly in this way. As above indicated, if one of them falls upon a leaf of a currant or gooseberry it is able to attack that leaf (fig. 4, a and I) . There must, however, be present a certain amount of moisture for the spore to germinate. Unless the weather is very dry, the neces- sary amount of moisture is usually present. In the presence of suitable moisture the tiny spore sprouts somewhat like a grain of corn. It sends its rootlike germ tube into the soft tissues of the currant leaf, and there it spreads within the leaf tissues until it has attained a certain amount of strength and has parasitized a small area of the leaf tissue. Temperature conditions control the rapidity THE WHITE-PINE BLISTER RUST. 13 of this development within the currant leaf. If it is abnormally cold, progress is relatively slow. If the temperature is warm the progress is rapid. With a favorable temperature, it requires 12 to 14 days for the parasite in its new home to produce a new crop of spores. These always appear upon the lower surface of the currant leaf in the form of tiny masses, hardly larger than a pinhead, of fine, orange-yellow powder (PI. I, B and C) . Each of these masses is the result of an infection of the leaf by a single Peridermium spore from the pine. Naturally, the number of these occurring upon a leaf depends entirely upon the number of Peridermium spores which have stuck to that leaf; in fact, they vary from a single one up to many hundreds on a single leaf. In many cases considerable areas of the leaf surface may be completely covered with the powdery, yellow spores, so plentiful has been the infection. These new spores, very curiously, are quite distinct in appearance from those on the pine from which they originated and are called uredospores. Unlike the Peridermium spores of the pine, which can not reinfect the pines, the uredospores of the currant leaf can reinfect currant leaves. This stage is for this reason called a repeating stage. The uredospores first produced from the Peridermium spores in turn are blown about and fall upon the leaves of adjacent currant or goose- berry bushes and there produce still another crop of uredospores. This repetition may go on all the rest of the season, a new generation of uredospores being produced every two weeks (fig. 4, 6 and c). This is the time when the disease spreads most rapidly and to the greatest distances. The progress made at this time, of course, depends entirely upon the presence of some currant or gooseberry bush near enough to the one originally infected so that spores will be blown from the one to the other. In many parts of the country currants and gooseberries are cultivated by nearly everybody who has a garden, and in those sections there usually occur from one to six or eight different species of wild currants and gooseberries in the fields, pastures, and forests; so that a census of the currants and gooseberries in a given locality often shows the best of opportunities for the disease in this stage to spread rapidly and for long distances. This stage of the disease is ordinarily found from June 1 until the fall of the leaves. From the latter part of July until the fall of the leaves still another form of fruiting body and of spores is produced upon the currant and gooseberry leaves. This may appear upon the same spots which have earlier produced the uredospores, but not always (fig, 4, &, c, and d). The new form appears as groups of 3 to 10 or 12 short, stout threads, not over a quarter of an inch in length and usually arranged in small circles (PI. I, D, and fig. 4). Upon these threads are produced spores of another distinct form. These are known as teliospores. These, 14 FARMERS' BULLETIN 742. unlike the uredospores, can not repeat their development upon the cur- rant leaves, but in order to carry on the disease they must attack the bark of young white pines or of young parts of old white pines (fig. 4, d and a). The teliospores, falling upon bark of suitable age on a white pine, may in turn germinate, penetrate the bark, and grow in the inner layers during the incubation period already mentioned. This infection of the pine bark must take place in the late summer or fall. If the parasite finds conditions very favorable, it may produce the sweetish drops of liquid with the pycnospores early the next spring, and shortly after that it may produce the blisters containing the Peridermium spores. The Peridermium stage is visible on the pines from the latter part of April until the middle of June. This com- pletes the life cycle of the parasite. Because of the fact that the Peridermium spores produced upon pine can not infect pine and that the teliospores produced upon currants can not infect currants, we immediately perceive that if the two sets of host plants are separated widely enough so that the spores produced upon one can not reach the other the disease can not spread. EFFORTS ALREADY MADE TO CONTROL THE WHITE-PINE BLISTER RUST. In Europe this disease was firmly established before any eradica- tion of plant diseases was attempted, and the only effort there exerted is merely to keep it in check. There has never been, pre- viously, either in Europe or America, any serious attempt to eradi- cate a disease of trees of this type; that is, we have had no earlier experience with a disease of this sort by which to guide our attempts at controlling this one. It was in 1909 believed feasible to remove all of the diseased trees from an infected lot of pines during the course of two or three years by repeated annual inspections in the spring when the fruiting bodies of the parasite are most conspicuous on pines. The work then attempted was done with this end in view. It has become increasingly evident since that time that such annual inspections would have to be repeated for an indefinite period, as it has been found that the parasite apparently may lie dormant in an infected tree for six or more years before becoming externally visible. This means that inspection is not efficient. The alter- native seems to be that of the total destruction of the entire lot of pines known to be infected. In the work done up to the present time, special emphasis has been given to the removal of all wild and cultivated currants and gooseberries from dangerous proximity to lots of pines known to be infected with the white-pine blister rust. It has been found, however, in these investigations that the various State officials, who necessarily must perform this work, do not have power to destroy such currants and gooseberries as may THE WHITE-PINE BLISTER RUST. 15 seem necessary in order to completely control this disease. The work for this reason has been greatly hampered and in many cases has not been carried out as it should have been. Many people have not realized the seriousness of this trouble, and unanimous action could not be secured. It is absolutely necessary that the State officers have complete power to enforce such measures as are needful for the control of this disease or their work will fail, just as it has failed up to this time. PRESENT STATUS OF THE WHITE-PINE BLISTER RUST. During the years 1909 to 1914, inclusive, the white-pine blister rust has been held well in control, considering the circumstances under which the work was carried on. In this period eleven distinct outbreaks of this disease occurred; that is, there were eleven differ- ent places where the disease spread from pines to adjacent currants or gooseberries. In these places the disease has been nearly or entirely eradicated. In 1915 the weather conditions were so favor- able for the growth of the parasite that it spread very readily on currants and gooseberries for relatively long distances. In 1915 alone twelve distinct new outbreaks occurred. The areas infected vary in extent from only a few currant or gooseberry bushes up to a single area of some 400 or 500 square miles. Unless very energetic action is taken to control the disease at once, it will shortly become impossible to do so. NEED FOR ADEQUATE STATE LAWS. As above indicated, there are a number of areas where this disease has spread upon wild and cultivated currants and gooseberries. It is entirely possible to stop its further spread by the mere removal of all wild and cultivated currants and gooseberries within the infected areas. The actual carrying out. of this work is not as difficult as is much of the work which is being done in the effort to hinder the spread of other diseases and pests. In carrying on this removal of currants and gooseberries, however, it is absolutely necessary that unanimous action be taken throughout the infected areas. Federal officers have no power to destroy private property in any State. This power is given solely to certain State officers, usually known as State horticultural inspectors. In most cases these State officers do not have power sufficient to compel unanimous action in such removal of currants and gooseberries. This power is one which every State should give to her proper officer at once if this work is to be efficiently done, and if such power is not thus given, this serious disease of white pines is certain to escape beyond any possible control and cause irreparable damage. WASHINGTON : GOVERNMENT PRINTING OFFICE : 1916 UNIVERSITY OF AGRICULTURAL EXPERIMENT STATION TIMELY HINTS FORFARMERS^ No. 118 JULY 15, 1916 CROWN GALL Crown gall is a widespread and dangerous disease, common to deciduous fruit trees. It also attacks a number of small fruits, some common field crop plants, and certain shade trees and orna- mentals. It is known to be caused by a bacterial germ. This organism, being minute, is easily spread from infected plants to healthy ones through various agencies, including rodents, insects (particularly borers), the careless use of pruning tools, irrigation, and cultivation. Appearance of the disease. — Knot-like galls or outgrowths appear commonly on the crown of the plant, a little below the surface of the ground. These are more or less smooth, but become uneven and roughened when old, and may Attain the size of one's fist. At the beginning of their growth they are milk-white, or translucent, but within a few months become brownish in color and often have a warty appearance. Smaller gall-like swellings from the size of a pea to that of a walnut often develop on some of the smaller roots, or rootlets, of the plant. These galls- appear on the roots and crowns of plants in early summer, but usually stop growth in the fall. This seems to be a matter of environment, however, for in warmer climates they may develop in the winter. They increase rapidly in size and cause a distinct malformation of the normal structure of the infected parts of the roots. Occasionally, as in the instance of the grape, pear, quince, rose bush, oleander, blackberries, and rasp- berries the galls grow on the stems, trunks, or limbs and hence may be seen readily. The trunks of certain varieties of quince trees are at times much disfigured with crown gall, though the tree may continue growth and bear fruit for some years. TIMELY HINT 118 There are other galls and gall-like growths on plants that may be mistaken occasionally by the nontechnical observer for crown gall. A careful study with a good lens or microscope, however, will reveal differences. Among these are galls on roots of apple and pear trees caused by the woolly aphis. These are small, quite irregular, and usually abundant on the roots of trees infested with this pest. The small insect can often be seen on them. The nematode gall is another peculiar outgrowth occurring on roots. These are irregular in size and shape. They are mostly quite herbaceous in texture, and when you»g are whitish in color. These are caused by small worms called nematodes which may sometimes be seen within the gall. They are often abundant on the roots Fig. 1. — Ciown gall, hairy root type, on root of apple trees from shipment into State of Arizona. A. W. Morrill, Fifth Annual Report, Arizonn Commission of Agr. and Hort. of tomato plants and are also found on many other plants. Nitrogen nodules should also be mentioned here as a form of root gall, though a beneficial one. They are well known to most growers and occur on the roots of plants of the legume or pea family. They are also found on a few other plants, including members of the Elaeagnaceae, of which the buffalo berry and Russian oleaster are members. The horticultural inspector, at least, should be able to recognize imme- diately these different galls. Professor Tourney, who worked on crown gall at this station some years ago, stated that when the gall first begins its development there is a pushing outward of a small area of the true cambium, or living tissue of the plant, which is later transformed into large mis- CROWN GALL 3 shaped cell tissues. In its youngest stages the gall is a mass of soft tissue with numerous minute areas of rapidly dividing cells scattered throughout. These areas of sub dividing cells are centers of growth, and as the galls become older these centers increase in size, and others originate in the newly formed cell tissues. Ultimately, these centers of growth become most curiously twisted nodules of woody fibers and similar tissues. The following year, fresh parts of roots become infected from the bacterial germs already in the diseased tissues. It has been shown that the galls developing on the roots of a tree, though separated by some little distance, may result from the original infection. Mr. Erwin F. Smith, of the United States Depart- ment of Agriculture, has called attention to the similarity ol growth and development of crown gall in plants, and malignant tumors, such as cancer, in animals. Injurious character. — Crown gall, when occurring on the main roots of plants, interferes with the movement of the cell sap and thereby weakens the growth of the tree. This shortens the life and the usefulness of the plant. The tap root and other roots which are attacked are usually killed within a few years. Apple trees, however, seem to be less injured than most other fruit trees. The tissue of the gall decays in time, and this gives opportunity for other parasites, including fire blight and root-rot, to develop and further injure the growth of the tree. When an infected tree dies in an orchard, and is replaced by a healthy one, the latter very commonly develops crown gall, which is evidence that the disease is easily transmitted through infected soil. More than this, diseased trees in an orchard are a means of infecting other similar healthy trees. Commoner plants which are attacked. — Crown gall attacks practi- cally all stone and pome fruit trees, including cherries, plums, peaches, apricots, quinces, pears, apples, and nectarines, also almonds, wal- nuts, chestnuts, grapes, blackberries, dewberries, raspberries, roses, chrysanthemums, white poplars, willows, hops, and sugar beets. On the grapes it is a very serious disease, one form of which is known as black knot. As early as 1880 it appeared in California vineyards, and later was brought to Arizona. Black knot may be recognized easily on the grape by the large, irregular black knots or galls, occurring at intervals on the vines. In different sections of our country it is quite common on the blackberry and the raspberry, occurring on the canes also. Occasionally it is found growing on alfalfa, haps, and sugar beets, but, excepting upon hops, it is not considered serious. However, such crops as these may be the means of infecting orchard and nursery lands. Little variety resistance has been found thus far among the different kinds ©f fruit trees, though much work remains to be done in this direction. Important inoculation experiments have been made regarding the bacterium causing crown gall. The results seem to indicate that all forms of crown gall are caused by the same bacterial germ, though the galls often vary in size and shape on different plants. Mr. Erwin F. Smith is of the opinion that the "hairy root" 4 TIMELY HINT 118 disease of the apple tree is caused by this same bacterium, or at least by a very similar one. How crown gall is spread. — It has already been observed that a few diseased trees in an orchard are sufficient to infect the entire lot. The germs are easily carried from one tree to another by ro- dents, including field mice, gophers, and rabbits, by insects (par- ticularly borers) , the careless use of pruning tools, and also through irrigation and cultivation. It should be a regular practice among nurserymen and orchardists to sterilize pruning tools frequently while using them. This may be done conveniently by dipping the blades of pruning shears, knives, and similar tools in a 4 or 5 per cent solution of formaldehyde and coating over with a small brush the blades of saws, pruning hooks, and such tools as can not easily be dipped. This can be done with small tools by immersing the blades in the formalin solution contained in a small vessel while passing from one tree to another. Fig. 2. — Crown gall on nursery tree sh pped into Arizona by mail. A. W. Moirill, Fifth Annual Report, Arizona Commission of Agr. and Hort., p 20 Trees, the roots of which have been damaged in carriage or in transplanting, are more easily infected with crown gall than similar trees the roots of which are in good condition, since the germs can easily gain access to the tissues of the plant through injuries. It would be a good practice to paint over the wounds (when these are of any considerable size) of the roots of young trees, with a thick lead paint. Orchard trees that have died from crown gall are a source of infection and should be destroyed. Also trees that appear to be unhealthy should be examined, and, if found affected with crown gall, should be destroyed. Root-grafted trees are more liable to CROWN GALL 5 crown gall than budded trees, since the bacterial germs gain entrance through the wounds made in grafting. For this reason orchardists should use, where possible, budded trees. Naturally, nurseries have played an important part in the spread of this disease. Often this has been done unconsciously. Nurseries should be inspected annually by State authorities. Nursery stock should also be inspected promptly before it is released to the cus- tomer. Fruit-growing communities, and home orchardists in States having no inspection laws, are always subject to the menace of receiving diseased stock from infested nurseries and from careless or indifferent nurserymen. Such communities should be doubly aware of the danger of buying nursery stock from any but thoroughly reliable nurseries. There are nurseries that are practically free from crown gall and similar diseases, as some nurserymen understand the nature of crown gall and use every possible means to prevent its introduction and spread. The names of such nurserymen can be se- cured from the State Entomologist's office. Not infrequently the soils of nurseries are infested with crown gall from past years' crops, and young nursery stock grown in such land is almost certain to be infested to some extent. Unfortunately, at this time, crown gall occurs in all agricultural districts of our State. It is safe to say that practically all of this was brought into the State originally through infected nursery stock. Crown gall is not only widespread in irri- gated sections of the West and Southwest, but occurs also in all fruit-growing regions of our country. Preventive measures.. — Preventive measures are more successful than methods of control. Orchardists and small planters should purchase their stock from reliable nurserymen. Inspectors should be authorized to refuse or destroy nursery stock that contains crown galled plants along with healthy ones. The removal of galls from the roots of young trees is not enough. Besides this, one does not have any assurance that some of the apparently healthy trees in lots with diseased ones will not develop crown gall later. The presence of more than 1 or 2 per cent of crown gall in young nursery stock suggests that the soil in which these trees were grown may be infected with crown gall, and hence some of the apparently healthy young trees may develop crown gall after being set out in the orchard. Nurserymen should become acquainted with the infec- tious nature of crown gall and use every means possible to keep this disease out of their nurseries. The grower should be willing to pay a reasonable price for nursery stock and insist upon receiving healthy trees. He should have the goods inspected by a person familiar with such diseases, as this may save him hundreds of dollars besides the loss of years of time. Generally speaking, it is preferable to purchase nursery stock from home nurseries where the plants may be seen growing in the row and be examined before being dug and packed. Home nurseries are less likely to have crown gall and similar diseases than larger nurseries, since ordinarily they carry a less diversified stock and they have more opportunity for extensive crop rotation. Pro- gressive home nurserymen will live up to the ideals of their com- 6 TIMELY HINT 118 munity and State. According to Dr. A. W. Morrill, all States except New Mexico require now an annual inspection of nurseries. Neither the orchardist nor the nurseryman should grow in orchards or among nursery stock, grapes, cane fruits, including blackberries, raspberries and dewberries or field crops that are subject to crown gall, since these plants may communicate this disease to fruit trees about them. In a small home orchard this would be less serious, as the loss would not be so great. The writer endorses heartily the work of the Arizona Commission of Agriculture and Horticulture in dealing with dangerous plant pests^ though some of the recommen- dations made here go farther in the matter of controlling crown gall. Nurserymen should practice a regular rotation of field crops, such as cereals, grasses, corn, cane and sorrghum, with their nursery tree crops, to prevent one crop of nursery trees from becoming infected from another. Nurserymen should select their plum, peach, apricot, almond, and similar pits for graft- ing and budding stock, from trees that are known to be healthy, rather than to buy such pits in miscellaneous lots from canning factories. They should select scion wood also, for budding and grafting, from healthy plants. Only recently we have come to appreciate the importance of selecting scions for budding and grafting from healthy trees, and it is equally important to select pits for grafting stock from healthy trees. At this time no definite remedy is known for crown gall, nor is there much hope for the discovery of one. The blue stone-copperas- lime paste has been used with some success as a treatment. This is recommended only for large trees, however, and is made as follows: Bluestone (copper sulphate) 2 parts. Copperas (iron sulphate 1 part. Unslaked lime 3 parts. These ingredients are reduced to a fine powder, after which they are carefully mixed together and enough water added to form a thick paste. This is applied with a small paint brush to wounds made by the removal of galls. In treating trees, the crown is exposed by digging away the soil to a sufficient depth. The galls are then cut away with sterilized pruning tools and the wounds coated over thickly with the paste. The soil is then shoveled back in place. The galls should be put in receptacles and destroyed as soon after as convenient. The crowns of trees thus treated should be examined several times during the season and if fresh galls appear these should be removed and the wounds treated as before. It is not recommended that one should treat a large number of orchard treees infected with crown gall with this paste with the idea of eradicating the disease. It may very well be applied to occasional large, heavy-bearing trees, which are removed some- what from orchards, to prolong their lives and thus enable one to get several crops more of fruit while other trees are brought into bearing. Such trees, however, should be destroyed as soon as their usefulness is past, since at best they are a menace to healthy trees. J. J. THORNBER, Botanist, Agr. Exp. Station. D5VIC5O UNITED STATES DEPARTMENT OF AGRJ& BULLETIN No. 49C Contribution from the Bureau of Plant Industry WM. A. TAYLOR, Chief Washington, D. C. PROFESSIONAL PAPER February 16, 1917 INVESTIGATIONS OF THE ROTTING OF SLASH IN ARKANSAS.1 By W. H. LONG, Forest Pathologist, Office of Investigations in Forest Pathology. CONTENTS. Page. Introduction 1 Methods of brush disposal 2 White-oak slash 3 Black-oak and post-oak slash 7 Shortieaf-pine slash 7 Page. The growth of wood-rotting fungi 9 Why brush in the center of the pile does not rot. . 10 General discussion 11 Summary 14 INTRODUCTION. Two very important factors must be considered in administering timber-sale areas, viz, the conservation of the present second growth and the leaving of the area in the best possible condition for future reproduction. The particular method of brush disposal over such areas is therefore of importance from the reproduction viewpoint. In the semiarid regions of the Southwest the dominant factor gov- erning reproduction is the obtaining and conserving of sufficient moisture to germinate the seeds and to carry the seedlings over the first four or five years of their existence. In the forests of Arkansas the conservation of the moisture is of minor importance, since the annual rainfall is usually sufficient to supply all of the moisture necessary for the germination of the seed and for the continued growth of the seedlings. Fire is a very important factor from a reproduction viewpoint in the National Forests of Arkansas. The Ozark National Forest consists almost exclusively of mixed stands of timber in which hard- 1The writer is under obligations to Mrs. Flora W. Patterson and Drs. E. A. Burt, C. L. Shear, and W. A. Murrill for assistance rendered in identifying many of the fungi mentioned in this bulletin. 66552°— Bull. 496—17 1 2 BULLETIN 496, U. S. DEPARTMENT OF AGRICULTURE. wood trees usually predominate, while the Arkansas National Forest is dominated by pines. The annual leaf fall front the deciduous trees accumulating year after year on the ground and the large growth of underbrush present constitute a perpetual fire menace. Even on areas in these two forests where shortleaf pine (Pinus echiiwtaY is being logged there are usually enough deciduous trees and underbrush present to make a ground litter from the fallen leaves, to which must be added the usual leaf litter found under pine trees. The method of brush disposal, that will give to the reproduction over these areas protection from fire and yet leave as much as pos- sible of the forest litter, leaves, twigs, etc., on the ground to rot, thereby adding fertility to the soil and protecting it against exces- sive erosion by restraining the run-off, is the one that should be adopted. The best method of brush disposal when the slash remains on logged areas is that which leaves the brush in such a condition that it will rot most rapidly, thus removing as soon as possible the fire menace from this source. METHODS OF BRUSH DISPOSAL. The three methods of brush disposal discussed in this bulletin are (1) pulling, (2) piling, and (3) scattering. By "pulling" is meant that the brush in the tops of the felled trees is not lopped, but is left exactly as the tree tops fall except when they fall on or near reproduction. When brush is too close to repro- duction it is pulled away from the young trees and merchantable timber, to decrease the danger from possible fire; hence the term " pulled brush." The terms " piling " and " scattering " are self-explanatory. Piling is the usual method of brush disposal followed in the National Forests of Arkansas. However, a few Forest Service areas were examined where the brush had been scattered as an experiment. In this State pulling the brush has not yet been practiced on Govern- ment sales, but on alienated or patented lands all of the brush in the tops of the felled trees is generally left as it falls. This is really a combination of " pulling " and " scattering," since the tops are left unlopped while the branches cut from the merchantable portion of the bole are scattered on the ground. The character and rate of rotting of the brush left on these private areas will therefore be the same as when the brush is pulled or scattered. This bulletin deals specifically with the rapidity with which the brush rots and with the fungi causing this rotting under each of 1 The nomenclature for trees used in this paper is that of George B. Sudworth. (Check list of the forest trees of the United States, their names and ranges. U. S. Dept. Agr., Div. Forestry Bui. 17, 144 p. 1898.) INVESTIGATIONS OF THE ROTTING OF SLASH IN ARKANSAS. 3 these methods. It will be necessary in discussing the various methods of brush disposal to take into consideration the types of timber being cut. In the Ozark National Forest the main timber is white oak (Quercus alba) intermixed with black oak (Q. velutina), post oak, (Q. stellata), and several other species of minor importance, while on certain areas some shortleaf pine is found. In the Arkansas National Forest the bulk of the timber to be logged is shortleaf pine. The investigations of the rotting of slash in Arkansas were car- ried on in the Arkansas and Ozark National Forests on areas which had been logged from 1 to 10 years. All of the areas examined which had been logged for more than five years were on private or patented lands, but located within these National Forests. The conclusions reached from these studies should be applicable to all of the other areas in these two forests, since the underlying principles are identical and the climatic conditions very similar. WHITE-OAK SLASH. FUNGI WHICH ROT THE SLASH. Four main fungi were found rotting the white-oak slash, viz, Stereum rameale, 8. versiforme, S. umbrinum, and S. fasciatum. All are sap-rotting fungi which cause but little apparent change in the texture of the wood. They produce what might be called indeter- minate rots, since there are no well-defined characteristics which mark any one of them. All slightly discolor the wood, which later becomes whitish in color, lighter in weight, and easily broken. Strange to say, each of these fungi rots its own special portion of the slash. Stereum rameale is usually found attacking twigs which bear the leaves and very small branches (1 inch or less in diameter). This fungus seems to begin on the twigs and works gradually down them to where the branches are about 1 inch in diameter; there two other fungi (S. versiforme and S. umbrinum) take up the work and rot the small branches up to 2 or 3 inches in diameter, where a fourth fungus (/S. fasdatum) usually begins its attack on the wood. This is the main fungus which rots the sapwood of the logs and large branches 3 inches or more in diameter, and it is often found rotting the sapAvood of the stumps as well as the boles and large branches of standing dead oak trees. None of these fungi destroys the attacked wood completely, its final disintegration being left to other groups of fungi, insects, etc. The heartwood of the large branches and trunks remains for many years after the sapwood is destroyed, but meantime it is being slowly rotted by a delignif ying fungus (Stereum frustulosum) , which pro- duces small cavities or pockets in the wood. Other fungi of minor importance were found attacking the oak slash, the most important of which was a small, dark-brown, gelat- 4 BULLETIN 496, U. S. DEPARTMENT OF AGRICULTURE. inous fungus (Exidia glandulosa] found at irregular intervals along the twigs and small branches. Its action on the wood is to produce whitish rotten areas, usually extending entirely through the branch, thus forming a line of weakness which ultimately causes the branch to break into small sections (2 to several inches long). These pieces fall to the ground, where complete disintegration follows. Merulius corium, Hymcnochaete curtisii, Diatrype stigma , and Stereum kirsutum are other fungi occasionally found attacking the twigs and small branches, while Merulius tremellosus, Polystictus pergamenus, P. versicolor, Polyporus gilvus, P. cinnabarinus, P. benzoinus, Lenzites betulina, Flammula sp., Panus stipticus, Stereum spadiceurn, Lycoperdon pyriforme-, Xylaria hypoxylon, and several species of Poria are occasionally found rotting logs, stumps, and large branches. Panus stipticus, Flammula sp., Mei^ulius tremellosus, Xylarria hypoxylon, and Lycoperdon pyriforme are fungi which apparently attack wood wrhich has been more or less rotted by other fungi. Polystictus pergamenus, P. versicolor, Polyporus gilvus, P. cinna- barinus, P. lenzoinus, and Lenzites betulina rot both the sapwood and heartwood, but unfortunately none of them are common on oak slash in the forests of Arkansas. None of the fungi found rotting the oak slash produces a heart rot in the living tree. However, cer- tain fungi which cause heart rots in living oak trees will continue to grow in the infected wrood after the trees are felled. The most impor- tant of these are Ilydnum erinaceus, Polyporus pilotae, P. sulphu- reus, and Stereum subpileatum. BRUSH WHEN PULLED. Soon after a living tree is felled, wood-boring insects and various fungi begin their work of disintegration and decay. The first evi- dence of fungous activity in slash is a discoloration of the sapwood in the twigs, branches, and trunks, which usually begins a few months after the trees are felled. Marked evidences of decay in the shape of well-defined rotten spots and areas in the wood and the formation of fruiting bodies or sporophores of the wood-rotting fungi do not appear until one or two years after the trees are felled. All of the leaves in the tops of felled oak trees will usually fall in from one to three years, depending more or less upon the age of the leaves at the time the oak was cut and to a slight extent on the locality in which the timber is situated. The small branches and twigs gradually rot, and the majority of them will have fallen to the ground at the end of four years. By the end of six years practically all of the branches in the tops will have rotted and fallen except some of the very large ones which have much heartwood. Also, practically all of the sapwood in the boles and cull logs will have rotted away during this time. INVESTIGATIONS OF THE SOTTING OF SLASH IN ARKANSAS. 5 BRUSH WHEN PILED. White-oak brush piles were examined, ranging from 1 to 5 years in age. During the first year after the trees were cut but little evi- dence of rot could be seen except a discoloration of the sapwood. By the end of the second or third year all of the leaves had fallen from the twigs which were exposed to the sun's rays, and the brush at the tops and sides of the piles where exposed to the sunlight had rotted to some extent, while the slash in the middle of the piles not in actual contact with the ground and yet protected from the sunlight was rotted but slightty, if at all. The twigs and small branches at the bottoms of the piles were more or less rotted by certain other fungi (called "ground" fungi in this bulletin), which apparently entered these branches from the soil. These ground fungi seem to rot the brush more rapidly and more thoroughly than the regular slash-: rotting fungi. Usually there is but little evidence of rot in the center of the piles during the first four years after piling. However, around the edges and through crevices in the top the sunlight sometimes penetrates sufficiently to permit slight fungous growth. Nevertheless, there is a marked difference between the rotting of the brush in the center of the piles not adjacent to the ground and that at the top and bottom of the pile. By the end of five years the top and bottom of the piles have rotted to a considerable extent, while the brush in the center of the piles, where it had become more or less exposed to the sun's rays, was beginning to rot. For the brush in the center of the piles to rot completely it appar- ently (1) must be brought within range of the soil moisture by the rotting of the brush below it and by the settling of the pile, or (2) the upper portion must disintegrate sufficiently for the sun's rays to reach the center of the pile. Undoubtedly, both conditions finally develop and aid in the rotting of the brush which was originally in the center of the piles. In a white-oak brush pile the layer of brush at the bottom would be the only one even in partial contact with the soil, while the remainder of the pile would be held from the soil by this first layer and therefore could not receive any benefit from the soil moisture. Neither are the piles dense or compact enough to raise the moisture content of the air around the brush in the piles sufficiently to encour- age the growth of the ground fungi in branches not in actual contact with the soil. On the other hand, the brush not in contact with the soil in the piles and yet sheltered from sunlight is deprived of the activity of the fungi which normally rot slash in the open ; that is, slash when left as it falls in the tree tops. 6 BULLETIN 496, U. S. DEPARTMENT OF AGRICULTURE. Since piles more than five years old were not found, the writer can not state positively the length of time necessary for a medium- sized compact brush pile of white oak to rot completely. Apparently it would take from three to six years longer than if the brush were either pulled or scattered. However, if the piles are very small, the brush will rot with about the same rapidity as when the tops are left unlopped, since the sunlight can then penetrate to the bottom. SPOEOPHOEE DEVELOPMENT ON PILED BRUSH. The difference between the development of sporophores at the top, middle, and bottom of brush piles is very marked. Practically every twig and limb at the top of the pile bore the characteristic sporo- phores of Stereum rameale, S. umbrinum, and S. versi forme on the rotting limbs, while no sporophores whatever were found on branches in the center of brush piles which were large and compact enough to 'exclude the sunlight. Very rarely were any sporophores of wood- rotting fungi found on the material at the bottom of the piles, although sterile mycelium was frequently present on the brush so situated. It was therefore difficult to determine what fungi were con- cerned in the rotting of the brush in the bottom of the piles. How- ever, sporophores were found of Merulius tremellosus, Peniphora flavido-alba, Odontia sp., Poria pulcliella, and two unidentified species of Poria. r BRUSH WHEN SCATTERED. When the brush is lopped and scattered it rots much more quickly than when piled, and in some localities somewhat more quickly than when left attached to the tops. On the areas examined the gain in the rotting of brush when scattered compared to that when pulled was usually about one year. When white-oak brush is scattered, only small portions of the limbs are actually in contact with the soil. The same fungi, therefore, that rot the unlopped brush will also rot most of the scattered brush, and with about the same rapidity. Brush lying on the ground sometimes absorbs from the soil suffi- cient moisture for the growth of ground fungi in those portions of the limbs which are in actual contact with the soil. On many of the areas examined the additional moisture obtained from the soil by the scattered brush was not sufficient to cause the 'ground fungi to attack the prostrate limbs. The influence of soil moisture on the branches lying on the ground usually does not extend more than 4 to 6 inches from the point where the limb is in contact with the soil. This means that the benefit to be derived from the ground fungi rotting a branch is limited to that por- tion directly in contact with the soil. On account of the small quan- INVESTIGATIONS OF THE ROTTING OF SLASH IN ARKANSAS. 7 tity of the brush thus situated, little of it is attacked by the ground fungi, and the benefits thereby derived are correspondingly slight. At the end of five to six years all of the brush (twigs and small branches) which was scattered will have rotted, and much of it will have disappeared. It was also no uncommon thing to find partially rotted brush, whether piled, scattered, or lopped, attacked by white ants (termites) and the partially rotted wood replaced to some extent by dirt. BLACK-OAK AND POST-OAK SLASH. Black-oak and post-oak slash was attacked by practically the same fungi which rot the white oak; however, but little of this type of slash was seen. The twigs and small branches of the black oak in most of the cases examined seemed to rot somewhat more slowly than white-oak slash of the same character, while the post-oak slash seemed to rot with about the same rapidity as the white oak. Polyporus cinnabarinus was occasionally found rotting the large limbs and boles of the black oak, while the small twigs and limbs of the post-oak slash were sometimes attacked by Schizophyllum com- mune, and cull logs and stumps were occasionally attacked by Lentinus lecomtei. Stereum ochraceo-flavum was the principal fungus found rotting fire-killed oak bushes 2 inches or less in diam- eter, while Polystictus pergamenus was the fungus usually found attacking fire-killed trees and fire-killed areas on standing living trees of all species of oak. SHORTLEAF-PINE SLASH. Shortleaf-pine slash was examined on areas which had been logged from two to nine years. FUNGI WHICH ROT THE SLASH. Two main fungi were found rotting the shortleaf-pine slash. One begins work in the ends of the small branches and works downward toward the trunk. This is usually Lenzites sepiaria, a dry-rot organ- ism prevalent throughout the United States. This fungus has never been found by the writer attacking slash which was not exposed to the direct rays of the sun. The second fungus enters the cull logs, boles of the tree tops, and branches 2 inches or more in diameter. It is what the writer pre- viously has called the " white-fir fungus " (Polystictus abietinus) -1 It is a sap-rotting organism and usually rots but little, if any, of the heartwood. 1 Long, W. H. A new aspect of brush disposal in Arizona and New Mexico. In Proc. Soc. Amer. Foresters, v. 10, no. 4, p. 383-398. 1915. 8 BULLETIN 496, U. S. DEPARTMENT OF AGRICULTURE. At the bottom of brush piles a fungus which has been identified as Polyporus amorphus was rather common. It apparently does not attack branches and limbs which are not in contact with the soil. Merulius ambiguus was occasionally found on small branches, while Fames annosus, Porla subacida, and P. vaporaria were found on large prostrate limbs, trunks, and stumps. Polyporus palustris, Fomes annosus, and Corticium gala^ctinum seem to be the principal fungi rotting the pine stumps. BRUSH WHEN PULLED. All of the needles in the tops* of felled shortleaf-pine trees will fall in from one to three years, depending somewhat on the locality in which the timber is located. The branches will gradually rot, and many of them will have fallen from the trunk at the end of three to four years. By the end of five years practically all of the branches, large and small, in the tops will have rotted and fallen to the ground. Also, most of the sapwood in the boles and cull logs will have rotted in this time. Pitchy limbs and trunks containing much resin rot very slowly and may be found long after the less resinous wood has dis- appeared. Polystictus abietinus and Lenzites sepiaria seem to rot branches which are 8 to 10 feet from the ground just as rapidly as those near the ground. Lenzites sepiaria also attacks decorticated logs and the exposed portions of railroad ties after they are laid in the track. BRUSH WHEN PILED. Shortleaf-pine brush piles were examined, ranging from 1 to 5 years in age. It was found that during the first year after the tree was cut but little rotting occurred, even in the small branches. By the end of the second or third year practically all of the needles had fallen from the limbs which were exposed to the sun's rays, while the needles in the middle of the piles, which were protected by the overlying brush, were in good condition and still attached to the limbs. In five years, brush at the top of the piles had practically rotted as far as the fungi which were attacking them could rot it, while the brush in the middle of the piles showed few signs, if any, of rotting. In the bottom of the piles the brush was well rotted, but by fungi different from those rotting the brush at the top of the piles. In other words, a brush pile of shortleaf pine will be rotted at the top by Lenzites sepiaria and Polystictus abietinus, the center of the pile will be rotted but little, while the brush at the bottom of the pile in contact with the soil will be rotted by certain ground fungi, one of which has been identified as Polyporus amorpJius. This means that before the center of the brush piles will rot, both the top and INVESTIGATIONS OF THE ROTTING OF SLASH IN ARKANSAS. 9 bottom of the piles must disintegrate sufficiently to expose the center of the pile either to the sunlight or to the moisture of the soil. This would probably add from three to five years at least to the length of time it would take to rot the slash in the brush pile as compared to that required if pulled or scattered. BRUSH WHEN SCATTERED. Practically the same conditions hold for shortleaf-pine slash when lopped and scattered as for oak slash; that is, the same groups of fungi which attack the pulled pine slash will attack the slash when scattered on the ground unless it be covered with leaf debris. Ground fungi will also attack that portion of the brush immediately in con- tact with the soil, provided the area under consideration is not too dry, like the south and southeast slopes of steep hillsides. In such locations no evidence was found of ground fungi attacking the scat- tered brush, or even the brush in the bottom of the piles. This means that the pine brush when lopped and scattered will rot much quicker than when it is piled, and on some sites slightly quicker than when left attached to the tops or pulled. THE GROWTH OF WOOD-ROTTING FUNGI. There is this physical factor to be kept in mind when considering the rotting of slash, viz, that the quantity of water which a limb or branch obtains is practically limited to the precipitation which that limb or branch receives and is able to absorb through its bark into the sapwood and that, so far as the amount of moisture in the wood itself is concerned, the humidity of the air around the branch would not be an important factor, since conditions would have to be very unique which would enable a branch covered with bark to absorb from the surrounding air a sufficient quantity of water to make any appreci- able difference in the water content of the branch or limb. This would mean that the distance the branch was from the ground, whether 1 foot or 5 feet, would make but little difference in the rela- tive supply of moisture obtainable from the atmosphere which the wood-rotting fungi in the branch could utilize. It might, however, determine to a slight extent the amount of moisture which the limbs could lose, especially in the bottoms of the piles. In regions of heavy dews the brush lying within 1 or 2 feet of the ground might obtain more moisture than brush farther from the ground. This indicates that the slash would have to be practically in con- tact with the soil to gain any appreciable quantity of moisture other than that obtained from precipitation, and from the very nature of the oak brush only small portions of any given limb would be thus placed. 10 BULLETIN 496, U. S. DEPARTMENT OF AGRICULTURE. Different groups of fungi seem to have adapted themselves to certain growth conditions. For instance, Stereum rameale and S. hirsutum were usually found only on the twigs and small branches, while S. umbrinum and 8. versiforme occurred mainly on twigs and branches 2 inches or less in diameter. None of these four fungi were found attacking large limbs and trunks of the felled trees, while S. fasciatum, very common on stumps and trunks, rarely occurred on branches less than 3 inches in diameter. None of them were found growing on timber which was entirely shaded from the sun. The fungi which rot that portion of the branches lying in actual contact with the ground under the brush piles belong to an entirely -different group. Such fungi apparently need a large supply of moisture and probably enter the wood from mycelia already growing and ramifying in the leaf debris in the soil. This group of fungi includes those which are normally found attacking wood partially or entirely buried in the soil, such as stumps and posts. WHY BRUSH IN THE CENTER OF THE PILE DOES NOT ROT. Why the fungi which are found attacking the limbs exposed to the sunlight wyill not usually attack the brush in the center or bottom of the piles when protected from the sun's rays is not known. Ap- parently temperature and moisture are not the only prominent fac- tors controlling fungous growth and activity in nature. Is it pos- sible that sunlight is a factor in the germination and growth of wood-rotting fungi in their natural habitats? In a previous article by the writer,1 the theory was advanced that the reason why the brush in the center and bottoms of the piles in the semiarid regions of Arizona and New Mexico did not rot was due to temperature conditions prevailing in the high altitudes. That the temperature in Arkansas could be a prominent factor in the rotting of the brush, or, rather, in the lack of the rotting of the brush in the middle of the piles, seems hardly possible, since the tempera- ture there is sufficiently high during a large portion of the year for fungous mycelia to grow vigorously, provided the other factors necessary for fungous growth are also present. The precipitation in Arkansas is sufficient to supply all the mois- ture necessary throughout the entire brush pile for the active growth of wood-rotting fungi. It seems, therefore, that enough moisture would persist in the center of the piles for the brush to rot at least as rapidly as the pulled brush. The fact that twigs and branches in the center of piles large enough to be shaded from the rays of the sun were the only ones not rotted seems to indicate that sunlight may possibly play a part in the rotting of the brush, not only in Arkansas, iLong, W. H. Op, cit., p. 395-396. INVESTIGATIONS OF THE ROTTING OF SLASH IN ARKANSAS. 11 but also in Arizona and New Mexico, where the same conditions as to the rotting of the limbs in the center of the piles were found to exist.1 It is very evident that certain groups of fungi capable of rotting the small twigs and branches of trees wrhich have died in the forest or of trees which have been felled are not capable of thriving under the conditions found in the center of large and compact brush piles. This is further accentuated by the fact that the bottoms of the brush piles in Arkansas, when rotted at all, are not rotted by these fungi, but are attacked by other fungi, such as Fomes annosus, which are known to live in more or less shaded and underground habitats. What the factors are that dominate the growth and activity of ( these various groups of fungi is not known. For instance, why is it that usually Stereum rameale and S. Mrsutum rarely attack limbs above 1 inch in diameter, while S. umbrinum and S. versi- forme are rarely found in limbs larger than 2 or 3 inches in diameter ? Why do not these fungi usually attack logs and large branches? Is the moisture content too high or the temperature too low? On the other hand, Stereum fasciatum, the common fungus rotting the cull logs and boles of the oak slash, usually does not attack the twigs and small branches. Of course, the explanation for this fungus might be that the twigs and small branches have not a sufficient amount of moisture, but such an explanation could not be offered for the failure of Stereum ramenle, S. versiforme, and S. umbrinum to attack the large branches and trunks. It would seem that but little is known concerning the real factors controlling fungous activity in wood. It is evident, however, that certain groups of fungi are capable of rotting the wood as it is nor- mally found in nature; that is, wrhen a tree dies, is killed by light- ning, or is wind thrown. These are conditions which have been oc- curring in nature through centuries, and certain fungi have adapted themselves to such conditions. The same could be said of limbs and logs which are in contact with the soil, or even buried in the soil, since such conditions are normal and found generally in nature. Apparently there are no fungi capable of vigorous growth under the artificial environments found in the center of large brush piles, where the conditions do not approximate those existing either when the brush is in contact with the soil or when it is exposed to the sunlight. GENERAL DISCUSSION. Several factors, such as fire, reproduction, and the rotting of the brush, are so intimately associated that it is impossible to discuss any one phase of brush disposal without noting, at least briefly, the i Long, W. H. Op. cit., p. 389-390. 12 BULLETIN 496, U. S. DEPARTMENT OF AGRICULTURE. possible influence of these other factors. It is obviously impossible to arrive at any legitimate conclusion concerning the best method of brush disposal by limiting the discussion to the pathological side of the question as seen in the rotting of the brush itself. The fire hazard, as it seems to exist in Arkansas, is therefore briefly discussed in connection with brush disposal from the pathological viewpoint. In the Arkansas National Forest about 3 to 5 white-oak trees are felled to the acre, and about 5 to 10 pine trees to the acre. In the Ozark National Forest the proportion of white-oak trees felled is somewhat greater, running probably from 5 to 10 trees to the acre, while there is but very little pine cut on this forest. This means that on any area in either of these two National Forests where timber is being cut, especially white oak, a much greater percentage of standing trees of all sizes, including those below the merchantable diameter limit, is left than is cut. This standing timber will add its annual quota of fallen leaves to the ground cover, irrespective of what method of brush disposal is followed. The amount of litter in the shape of slash, on account of the small number of trees cut per acre, in many cases will not make fires more likely to start or prevent their control, since there will always be a sufficient quantity of leaf litter and underbrush present to make a good ground fire, even if there be no slash on the ground. If the deciduous trees are cut with the leaves on them the amount of leaf litter will not be increased, since these leaves would fall to the ground in the autumn even if the trees were not cut; in fact, there would really be less leaf litter on the ground, because the leaves persist on the felled tree tops and branches from one to three years. There is also this fact to be borne in mind, that oak trees cut from November to March, inclusive, are leafless or practically so, and the brush from them will not materially increase the fire hazard unless it is piled. In 1912 and 1913 the writer visited areas in the Ozark National Forest which were then being logged. In the studies made in 1915, only two to three years later, many of these areas had been burned over. It can probably be said truthfully that the greater portion of the Ozark National Forest, except about 100,000 acres in the middle of the central division, will be burned over at least once within a period of five years, and often within a much shorter interval. It seems, therefore, that whatever system of brush disposal is followed in this forest should take into consideration the certainty of fire as well as the rotting of the brush. In the Arkansas National Forest many areas are not burned over more than once in every 20 years. Under such conditions the rot- ting of the brush is the main factor to be considered. INVESTIGATIONS OF THE ROTTING OF SLASH IN ARKANSAS. 13 No areas were seen on which brush had been cut and scattered where there had been fire. What effect, therefore, a fire would ha\?e on such areas as compared with those on which brush had been piled or pulled can not be stated from actual observation. However, areas were seen on which there had been fires where brush had either been pulled or piled. Many trees whose tops had been left with the limbs unlopped were seen with the needles or leaves burned from only the lower half of the tops. This leaving unburned the leaves and needles in the upper half of the felled tree tops seemed to indicate that fires in the forests of Arkansas in pulled brush do but little, if any, more damage than the regular ground fire which is fed by the normal annual leaf debris and underbrush. Many areas on which the brush had been piled were seen where forest fires had killed a large portion of the young reproduction up to 4 inches in diameter. Brush when lopped and piled rots much more slowly than under either of the other methods of disposal. Such piles may be expected to persist from three to six years longer than the same brush when pulled or scattered, depending upon the size and compactness of the piles. This would eliminate the large brush piles from consideration in disposing of the slash on these areas. The best method of brush disposal over such areas would be that which is the least expensive, which reduces to a minimum the damage to the forest when fires occur, and which leaves the slash in such condition that it will rot most rapidly. It is very evident in view of these three things that the lopping and piling of the brush is the poorest method to follow, since not only is it the most expensive, but brush when piled rots the slowest and the reproduction on such areas is apparently damaged most by forest fires, judging from the burned areas seen. This would leave the choice between scattering and pulling. Pulling, as practiced in coniferous timber, would not be practicable in certain types of hardwood sales, such as stave sales, since the oak tops are usually too heavy to be moved as a whole by the methods of logging in use on such areas. However, when tree tops fall near reproduction or near trees to be left, it is immaterial whether the top is pulled away by a team or by hand or whether the objectionable sections of the top are sawed out and rolled away. Brush when pulled or left in the tops rots with nearly the same rapidity as when lopped and scattered. The difference in time be- tween the rotting of the pulled and of the scattered brush is appar- ently about one year in favor of the scattered brush. Whether a possible maximum gain of one year in the time of rotting between the brush that is pulled and that which is scattered is sufficient to offset the difference in cost between these two methods must, of course, be considered. 14 BULLETIN 496, U. S. DEPARTMENT OF AGRICULTURE. SUMMARY. (1) When the brush is lopped and scattered it rots more rapidly than when either piled or pulled. This is due to the fact that two types of fungi rot the brush, one entering the limbs and branches not in direct contact with the ground and the other entering those portions of the brush in actual contact with the soil. (2) The maximum gain in the rapidity of the rotting of the brush when scattered over the same brush when left unlopped in the tree tops is about one year. On dry areas, such as steep hillsides with southern and western exposures, ftiere is practically no difference in the rate of rotting of the brush when scattered and when the tree tops are left unlopped. (3) Brush when lopped and piled will apparently take from three to six years longer to rot than wThen scattered or when left unlopped. (4) Brush when piled is rotted at the top by one group of fungi and at the bottom by another group, while the middle of the pile, not in contact with the soil and yet protected from the sunlight, ap- parently will not rot to any extent until the pile disintegrates suffi- ciently to expose these central layers to the soil moisture on the one hand or to the sunlight on the other. (5) The same general facts as to the rotting of the slash hold for all species of timber (pine, oak, etc.) examined in Arkansas. (6) Four fungi are the main agents in the rotting of oak slash in Arkansas, viz, Stereum rameale, S. umbrinum, S. versiforme, and S. fas datum. (7) Two main fungi rot the shortleaf-pine slash, viz, Polystictus abietinus and Lenzites sepiaria. (8) No definite conclusions could be reached concerning the prin- cipal fungi which rot the bottom of the piles, since but few sporo- phores of such fungi were found. (9) None of the main fungi concerned in rotting either the oak or the pine slash in Arkansas produce heart rots in living trees. PUBLICATIONS OF THE U. S. DEPARTMENT OF AGRICULTURE RELATING TO DISEASES OF TREES. AVAILABLE FOR FREE DISTRIBUTION BY THE DEPARTMENT. The Death of Chestnuts and Oaks Due to Armillaria mellea. (Department Bul- letin 89.) The Life History of Lodgepole Pine in the Rocky Mountains. (Department Bulletin 154.) Life History of Shortleaf Pine. (Department Bulletin 244.) A Disease of Pines Caused by Cronartium pyriforme. (Department Bulletin 247.) The Care and Improvement of the Woodlot. (Farmers' Bulletin 711.) The Preservative Treatment of Farm Timbers. (Farmers' Bulletin 744.) Fire-Killed Douglas Fir: A Study of Its Rate of Deterioration, Usability, and Strength. (Forestry Bulletin 112.) Practical Tree Surgery. (Separate 622 from Yearbook, 1913.) Forest Tree Diseases Common in California and Nevada. (Forest Service, Mis- cellaneous Publications.) FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS, GOVERNMENT PRINTING OFFICE, WASHINGTON, D. C. The Control of the Chestnut Bark Disease. (Farmers' Bulletin 467.) Price, 5 cents. Sap-Rot and Other Diseases of the Red Gum. (Bureau of Plant Industry Bul- letin 114.) Price, 15 cents. The Mistletoe Pest in the Southwest. (Bureau of Plant Industry Bulletin 166.) Price, 10 cents. The Timber Rot Caused by Lenzites sepiaria. (Bureau of Plant Industry Bul- letin 214. ) Price, 10 cents. Forest Pathology in Forest Regulation. (Department Bulletin 275.) Price, 10 cents. 15 ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 5 CENTS PER COPY FOE COLLEGE ' HYPODERMA DEFORMANS, AN UNDESCRIBED NEEDLE FUNGUS OF THE WESTERN YELLOW PINE By JAMES R. WEIR, Forest Pathologist, Office of Investigations in Forest Pathology, Bureau of Plant Industry INTRODUCTION In the summer of 1913 the writer's attention was drawn to what appeared to be a very serious needle disease of the western yellow pine (Pinus ponderosa Laws.) in parts of Idaho, Washington, and Montana. That the disease has become more prevalent is shown by the receipt at the Laboratory of Forest Pathology at Missoula, Mont., of many collec- tions of the fungus from localities where it was not before known to exist. These collections represent material from trees of all ages and show the youngest needles as badly diseased as the oldest ones. The first suspicion that the fungus might be of some economic importance arose through the discovery of a serious infection of young reproduction over a large area in the Whitman National Fore'st, Oregon. From the fact that the fungus causes a conspicuous hypertrophy by the extension of its mycelium into the tissues of the twigs and also through the destruc- tion of the youngest needles, consequently causing in some localities much damage in the forest, it seems desirable to make known its char- acteristics. TECHNICAL DESCRIPTION OF THE FUNGUS Since the fungus does not agree with any known member of its genus, it is described as new. Hypoderma deformans, n. sp. Apothecia black, shiny, averaging 10 mm. in length and i mm. in breadth; may extend as a black line the entire length of the sheath side of the needle or be broken up into a series of shorter apothecia, usually arranged along the middle line of the needle, but may appear at either side and be very rarely confluent with the more medially arranged apothecia; opening with a longitudinal medial split. Asci fusiform (26) 26.1 to 43. 5M by 159.5 to 207. 2/x (27.3 to 2g.o/j. by 171.5 to i86.4ju). Spores parallel or obliquely arranged in the ascus, very generally slightly curved, uniform breadth, rod -shaped, ends blunt, i- septate when mature, septum very conspicuous, cells often apparently separated, pale olive, almost hyalin, eight to an ascus (40) 6.2 to Journal of Agricultural Research, Vol. VI, No. 8 Dept. of Agriculture, Washington, D. C. May 22, 1916 dn G — 79 (277) 278 Journal of Agricultural Research Vol. VI, No. 8 9.7/1 by 90.67 to 131. 37/z (7.4 to 8.7,u by 108.9 to 117. 6/*); paraphyses numerous, fila- mentous, swollen at the ends or recurved. Spermogonia intermixed averaging 5 mm. in length; spermatia elongated, straight, sometimes slightly curved, hyalin, contin- uous, averaging i by 8^. Type locality: Sumpter, Oreg., Whitman National Forest. Habitat: Living needles of Pinus ponderosa. Type material deposited in the Office of Investigations in Forest Pathology, Bureau of Plant Industry, Washington, D. C., and in the col- lections for study in the Laboratory of Forest Pathology in the same office, at Missoula, Mont. GENERAL BIOLOGY OF THE FUNGUS The apothecia of the fungus are the most conspicuous of any of the group on pines in the West (fig. i). From new infections of the previous year fully mature apothecia with well-developed spores (fig. 2) may be collected in early spring. From this time on the longitudinal split on the medial line of the apothecium is plainly visible, and may remain open or closed, depending on the humidity of the atmosphere. FIG. i. — A side view of two apothecia of Hypoderma deformans on needles of Pinus ponderosa, showing the longitudinal medial split. The splitting of the epidermis on the needle directly on the medial line of the apothecium is a characteristic shown by nearly all of the Hysteriaceae and in a few cases seems to be governed by a particular structure of the overlying layers of the apothecium. Thus, Von Tubeuf 1 points out that the pseudoparenchymous covering of the apothecium of Lophodermium pinastri (Schrad.) instead of being one continuous homogeneous tissue is made up of two parts which come together on the middle line of the fruiting body. The edges of the two parts interlock by a series of short papillae. It is on the line of these papilla, when the pressure within the apothecium becomes sufficient, that the epidermis of the needle ruptures. In Hypoderma deformans the rupture of the apothecium is apparently made easier by the coalescence of filamentous elements springing from the floor of the apothecium and meeting with the darker tissues of the apothecial covering above. Owing to a differentiation of the covering of the apothecium at the point of union a line of rupture is formed. 1 Tubeuf, Carl von. Studien xiber die Schiittekrankheit der Kiefer. In Arb. Biol. Abt. I>nd- u. Forstw. K. Gsndhtsamt., Bd. 2, Heft i, p. 22, 1901. May 22, 1916 Hypoderma Dejormans 279 Pressure within the apothecium on approaching maturity, together with the elongation of the central elements, causes the rupture to occur on this line. After initiating the line of rupture, the filaments disappear and no sign of their presence exists when the spores are mature. In all material so far examined this mechanism is a constant characteristic. Where two apothecia are formed side by side, the filamentous structures are in marked contrast to the division line between the two apothecia as formed by the union of the darker colored elements of the apothecial covering. Von Tubeuf found in Hypoderma strobicola Tub. (Lopho- if. T mm FIG. 2. — Asci, spores, and paraphyses of Hypoderma deformans. dermium brachysporum Rostr.) the same structure which he describes for Lophodermium pinastri (Schrad.), but no such structures were found in H. deformans. Apothecia with mature spores (fig. 3) may be found at any season of the year. This is due to the fact that the spores do not ripen or are not all freed simultaneously when the split first appears in the apothecium. The process of spore liberation is observed to extend over a long period of time. A year may elapse before the apothecia have entirely liberated their spores. During periods of drought the medial slit in the apothe- cial covering remains closed, only opening on the return of abundant 280 Journal of Agricultural Research Vol. VI, No. 8 moisture. The hygroscopic movements of the lips of the apothecium furnish the method by which the spores are forced or ejected from the asci. As Von Tubeuf 1 has pointed out in the case of Lophodermium pinastri, the spores are shot out from the mature asci under proper con- ditions of moisture. This fact is easily demonstrated by inclosing short pieces of previously moistened needles bearing mature apothecia in the cavities of plate-glass culture slides. A microscopic study of such preparations shows that the spores are shot out from the asci a distance of from i to 2 mm., showing as a plainly visible deposit on the floor and cover of the cavity. The depth of th£ cavity in the slides used was 2 mm. mm FIG. 3. — Cross section of an apothecium of Hypoderma deformans on a needle of Pinus ponder -osa, showing mature asci with spores, the point of first rupture, and the tissues of the leaf most seriously affected by the mycelium of the fungus. Occasionally an entire ascus was ejected and lay among the spores. In most cases, the asci remained attached and the spores were expelled through their terminal pores (fig. 4). Only the fully developed spores were cast out of the apothecia. After the material had remained in the slides a day and a half, during which time the spores were being ejected, the cover glass of a slide was removed and the material allowed to dry by exposure to the air of the laboratory for 30 days. The material was washed and replaced in the cavity in the slide. Within three hours spores from the same apothecia were expelled in considerable numbers but not so profusely as before. The process was repeated with shorter 1 Tubeuf, Carl von. Op. cit., p. 24-25. May 22, 1916 Hypoderma Deformans 281 periods of drying till on the fourth trial no spores were liberated. An examination of the apothecia showed the asci to be entirely empty. This experiment not only demonstrates that the fungus has the ability to resist protracted periods of dryness but that the period of spore libera- tion may be much protracted, depending upon the atmospheric humidity. During wet weather apothecia expel their spores in visible quantity when a sharp blow is given the branch bearing infected needles. Considering the long periods of drought in most yellow-pine regions, it is safe to assume that an apothecium ripening in early spring may first become emptied of its spores during the ensuing winter or even later. This is important for the propagation of the fungus, since new infections are possible from the time the first needles of the season appear till the close of the growing season. In order to determine the viability of the spores expelled from apothecia after long dryness, a 2 per cent sugar solution was introduced into the cavity of one of the slides containing apothecia which had lain dry in the laboratory for two months and the slide placed in the thermostat at 35° C. On the fourth day spores germinated readily. The germ tubes appeared more frequently from the ends of the spores. A slight addition of an extract of pine needles to the sugar solution promoted germination. It was noticed that in collections of the fungus made shortly after warm summer rains the asci are frequently empty as compared with asci of mature apothecia collected in the colder spring months. This, it seems, may not be entirely due to a longer period of spore liberation but also to the higher tem- perature of the summer months. Von Tubeuf found that increasing temperature promoted spore liberation in Lophodermium pinastri and it is found to be true in experiments with the yellow-pine fungus. During the winter, moistened apothecia from dry material were mounted in two culture slides; one was placed outside the laboratory during a period when the thermometer registered about 40° F. and the other was kept in the laboratory air of about 80° F. At the end of four hours a microscopical examination showed that a large number of spores had been ejected from the apothecia in the slide kept in the laboratory but none from the other slide. When the slide from the outside was allowed to stand for a while in the warm air of the laboratory, spores were liberated in quantity. Although spores from various needle fungi are undoubtedly more readily liberated during warm rains of the summer months, the frequent drying of the foliage of the trees is probably not favorable for infection. It is frequently observed, and as often reported, that needle fungi become more active during the cool, protracted rainy periods of early spring and late fall. No extensive data are at hand regarding the resistance of FIG. 4. — The upper por- tion of a young ascus of Hypoderma deformans, showing the formation of the pore at the tip through which the spores are expelled. 282 Journal of Agricultural Research vol. VI.NO.S expelled spores to drought and direct light; still, the fact that dry her- barium material a year old was found to furnish viable spores shows that spores may exhibit considerable resistance to dry air when free from the apothecium. PARASITISM OF HYPODERMA DEFORM ANS An attempt to grow the fungus on culture media failed. The spores in every case germinated and in some cases produced an abundant white mycelium, but in the course of six months, after frequent transfers, the mycelium turned a light yellow and died. A somewhat better result was obtained by adding to the culture medium a strong extract made from yellow-pine needles in water, but at the end of eight months the mycelium died. A quantity of needles bearing apothecia with mature spores were col- lected in the spring of 1914 near Missoula, Mont., and taken to the field station in the Priest River Valley, Idaho, for experiments on parasitism. The fungus has not been found in this region. The needles were thor- oughly washed in distilled water and the apothecia allowed to expel their spores in small sterilized flasks. Needles and spores were shaken up in water to which a i per cent sugar solution was added. The mix- ture was allowed to stand one day and then thoroughly sprayed over four 3-year-old yellow-pine seedlings having young tender shoots with needles. The inoculated seedlings were immediately inclosed in tough, transparent oiled paper bags and protected from injury. A second ex- periment was initiated by binding infected needles on healthy 3 -year-old seedlings. In the part of the Priest River Valley where these experi- ments were performed the yellow pine is not common, being only spar- ingly represented in a mixture of white pine, grand fir, spruce, hemlock, and Douglas fir. The experiments were made on May 20. In Septem- ber the last-formed needles of the inoculated seedlings were turning reddish brown in spots, mostly at the tips. In the following spring, May to June, the needles which showed infection in the fall and which had become wholly brown developed the characteristic long, shiny black apothecia with mature spores (PI. XXXII, fig. i). Only the needles formed during the previous year were infected. Four control plants, also covered with bags, were entirely free from the disease. The needles of the seedlings on which infected needles were bound showed a much more general infection of the last-formed needles than those by the former described method. In these experiments every needle produced in 1914 was infected. Those of previous years remained healthy. This indi- cates that old needles are riot attacked and that the young needles may remain attacked indefinitely after infection. All the infected needles did not produce mature apothecia. Those merely turning brown were filled with the mycelium of the fungus. The experiment at this point was discontinued. In all probability, given time enough, the brown-infected needles would have produced apothecia. May22,i9i6 Hypoderma Deformans 283 It has been noticed repeatedly in nature that there is great irregularity in the time between the first browning of the needles at their tips or at other points along the needles and the appearance of the mature apothecia. In a few cases the cycle of development from the first appearance of the brown color at the tips of the needles to mature apothecia has been observed to take place within the same calendar year, or from April and May to November. More often infected needles first showed mature spores in the spring of the following year. It was observed in a few cases that the needles may lie on the ground through the following winter before the apothecia rupture. Brown needles collected in August from infected trees and placed in damp moss in the field in a number of cases developed apothecia before January, maturing in May and June. The apothecia, as previously indicated, may contain asci in various stages of development, so that mature spores are being produced throughout the year. Investi- gation has shown, however, the greatest number of spores are expelled during the spring rainy season, May and early June, coinciding with the greatest vegetative period of the host. In no instance, either in the field or in artificial inoculation, were the infected needles of young trees or seed- lings not previously attacked by the fungus killed before they had attained their normal size. In September or October, such needles will have assumed a more or less uniform reddish brown color. Mostly remaining upon the tree, they may first produce the signs of the apothecia during the late fall and mature the spores in the following spring. At the time the foregoing experiments were in progress small bundles of infected needles bearing fertile apothecia were bound with similar quantities of needles which had died from a normal cause. These were placed in moss during May, 1914. On examination in May of the following year the needles which had died from a normal cause showed no signs of the fungus; nor have they done so since that date. This apparently demonstrates the inability of the fungus to act as a saprophyte. The foregoing observations and experiments apparently prove the parasitism of the fungus. This is further substantiated by the observed evidences that young seedlings in the field succumb to the ravages of the fungus. Furthermore, it is indicated that the period of greatest infection is during the growing season and only the needles of the season are to any extent susceptible to attack. The fungus has not yet appeared in the forest nursery, but it may be regarded as a possible nursery disease. PATHOLOGICAL EFFECTS OF THE FUNGUS ON THE BRANCHES OF THE HOST A very peculiar and at the same time interesting phenomenon caused by the growth of the mycelium of the fungus in the shoot is the formation of spherical-shaped witches'-brooms on trees mostly past the seedling stage. These (PI. XXXII, fig. 2) brooms in old trees often assume large proportions. A single witches' broom may weigh as high 284 Journal of Agricultural Research vol. VI.NO.S as 100 pounds and measure 5 or 6 feet in diameter. The branch sup- porting it will hang vertically, the broom swaying in the wind like a great bag (PI. XXXII, fig. 3). The average size of the brooms is about 2 feet in diameter. Although a few isolated cases had been noted on the seeming association of this needle fungus with these compact brooms, it was not until the field season of 1913 that this association was found to be of common occurrence. This was all the more interesting from the fact that the cause of these formations has been a standing question with all who have seen them. In some cases they have been attributed to the yellow-pine mistletoe, Raz), the spores com- pressed, and the columns where partially developed were coiled or bent by the pressure on the free ends (Pi. 88, C}. Despite the distortion of the columns, the spores quite closely resembled the spores from a normal sorus, lacking, however, in many cases, the heavier brown wall, char- acteristic of the fully developed spores of an external column. Possibly the walls would have taken on the brown color as the spores matured. In several of the sori, older than the others, the spores were just begin- 1 Dr. Perley Spaulding, of the Office of Forest Pathology, supplied the material for this study, and kindly furnished the data on the inoculation. Feb. 26, 1917 Internal Telia Produced by Cronartium sp. 331 ning to develop the wall thickening and color change. The walls of the spores at the tip of the telial column shown in Plate 88, C, were identical in color and thickness with the walls of spores in external columns. The measurements of the internal spores, 10 to 20 by 20 to 40 n, agreed well with those of normal spores, considering the conditions under w^hich the internal spores wrere produced. There was at first some doubt as to the true nature of the spores, for some of the sori were surmounted with a peridium like the peridium of a normal uredinium. This would not exclude the possibility that the sorus was a telium, for the normal telial column often arises from an old uredinium. In this case, indeed, there could be no question whether the spores were urediniospores or telio- spores, since the mycelium, which, as mentioned above, sometimes stuffed the pith region, was typically binucleate; the spores were uni- nucleate; and the change from the binucleate condition to the uni- nucleate condition occurred just after the spores were cut off from the basal cells of the sorus. This cytological evidence, agreeing as it does with cytological conditions in sori producing teliospores, completely established the identity of the internal sori as telia, even when the spores were very young. The occurrence of the petiole infection is rather common in both wild and cultivated species of Ribes where the general infection is heavy. In two other species examined, R. nigrum L. and R. cynosbati L., no internal telia had been formed, although the mycelium was abundant and normal telia present on the surface of the petioles. The epidermal region of the petioles of Ribes spp. undoubtedly offers more resistance to the developing telia than the epidermis and palisade cells of the leaf. The sori probably are unable to break through the stiffer layer in the petiole; hence, their development as far as possible within the inclosing tissue. Unquestionably internal sori should be regarded as rather common teratological phenomena, developed in spite of their unfavor- able position. Morphologically they have no special significance. Their development is to be expected whenever the point at which the sorus begins to form is located beneath a layer of tissue which offers a greater resistance than the developing sorus can overcome. Accidental discov- ery of the sori after the material had been killed and embedded has pre- cluded any spore germination experiments. Investigators, however, have found the internal mycelium, and the teliospores themselves, to be in a living state after a considerable time, even in comparatively dry tissue. Pritchard (5) figures the teliospores as undergoing a sort of palmella-like division which may be the equivalent of germination. In his material the mycelium was certainly alive for a long time. There is a possibility that the phenomena described by Pritchard (5) might be observed under suitable conditions in the internal teliospores of Cronar- Hum ribicola. 332 Journal of Agricultural Research vol. vm, NO. 9 SUMMARY (1) All four types of rust sori have been found developing internally in the host-plant tissue, producing spores which appear quite normal and which fill intercellular spaces or force aside the softer tissue. (2) The fact that Cronartium ribicola Fisher produces internal telia is here reported for the first time. These telia form spores inside the petioles of species of Ribes, chiefly in the pith and pericycle region. (3) Internal sori should be regarded as rather common teratological phenomena. LITERATURE CITED (1) ADAMS, J. F. 1916. Internal uredinia. In Mycologia, v. 8, no. 3, p. 181-182, pi. 186. (2) BOLLEY, H. L., and PRITCHARD, F. J. 1905. Internal infection of the wheat grain by rust — A new observation. In Science, n. s. v. 22, no. 559, p. 343-344- (3) FROMME, F. D. 1912. Sexual fusions in the flax rust. In Bui. Torrey Bot. Club., v. 39, no. 3, p. 113-131, pi. 8-9. (4) • 1914. The morphology and cytology of the aecidium cup. In Bot. Gaz., v. 58, no. i, p. 1-35, 8 fig., pi. i-2. (5) PRITCHARD, F. J. 1911. A preliminary report on the yearly origin and dissemination of Puccinia graminis. In Bot. Gaz., v. 52, no. 3, p. 169-192. pi. 4. Cites W. J. Smith (p. 173). (6). . 1911. The wintering of Puccinia graminis tritici E. and H. and the infection of wheat thru the seed. In Phytopathology, v. i, no. 5, p. 150-154. 2 fig., pi. 22. (7) WOLF, F. A. 1913. Internal aecia. In Mycologia, v. 5, no. 6, p. 303-304, pi. in. PLATE 88 A. — Cross section of a petiole of Ribes roezli, showing the pericycle (a) and pith (6) regions which are stuffed with the mycelium of Cronartium ribicola. Most of the pith cells have been destroyed. Teliospores partially fill the cavity. B. — Longitudinal section of the same petiole, showing the manner in which the sori force aside the parenchyma cells of the pith. C. — Internal telium of Cronartium ribicola from the pericycle region of a petiole of Ribes roezli. The telium has been forced to coil on account of the pressure of the surrounding cells. D. — Internal telium of Cronartium ribicola from the pericycle region of a petiole of Ribes roezli flattened by pressure. E. — Young internal telium of Cronartium ribicola from the center of the pith region cf a petiole of Ribes roezli, illustrating the depth at which sori may start to develop. Internal Telia Produced by Cronartium sp. PLATE 88 Journal of Agricultural Research Vol. VIII, No. 9 Reprinted from PHYTOPATHOLOGY, Vol. VI, No. 3, June, 1916 PERIDERMIUM HARKNESSII AND CRONARTIUM QUERCUUM1 E. P. MEINECKE WITH Two FIGURES IN THE TEXT INTRODUCTION Peridermium harknessii was first reported on the Pacific Coast on Pinus radiata by Moore; Farlow and Seymour's2 Host Index adds P. contorta, P. ponderosa and P. sabiniana to the list. Hedgcock3 further reports it on P. jeffreyi. The writer has found it very common on Pinus attenuata, and occasionally also on P. coulteri. Of all these hosts P. radiata, sabiniana, attenuata and contorta are undoubtedly most subject to attacks from the fungus. Numerous galls appear on the same tree. The writer has counted thirty-seven galls on a sapling of Pinus radiata, three feet high, selected at random from a group of similarly affected trees. Another specimen contained thirty-four galls on a witches'- broom fourteen inches high which had developed from a large old gall on the main stem. Another tree (diameter at base three inches, height eight feet) had 173 galls. A fourth tree (diameter at base six inches, height twelve feet) carried not less than 529 galls. There can be little doubt but that each gall is the result of an individual infection. The tissues, even between neighboring galls, are perfectly nor- mal, and rather commonly a tree develops only one gall, which may grow to large size. Unless the mycelium kills its substratum, as is often the case, it may grow and cause the gall to enlarge for many years, but it is always strictly confined to the gall itself and its immediate surroundings. 1 A preliminary note appeared in Science, n.s. 43: 73. 1916. 2 Farlow, W. G. and Seymour, A. B. A provisional host index of the fungi of the United States, Part III, pp. 160-162. 3 Hedgcock, G. G. Notes on some western Uredinae which attack forest trees. Mycologia 4: 143. 1912. 226 PHYTOPATHOLOGY [VOL. 6 The mycelium is unable to spread from the initial point of infection and thus produce a gall at some distant point. The typical Peridermium harknessii very much resembles Peridermium cerebrum Peck. Since Shear4 has proved that Peridermium cerebrum has as its alternate stage Cronartium Quercuum (Berk.), the occurrence of a Cronartium on Quercus agrifolia in California5 made it appear possible that the two Peridermia were identical. Hedgcock and Long6 call the eastern form on oak Cronartium cerebrum. The identity of the Calif ornian Cronartium on oak with the eastern form not being definitely proved by inoculation, the old name Cronartium Quercuum in Shear's sense is, for convenience's sake, used in this paper. The writer has found Cronartium Quercuum in its telial form in the im- mediate vicinity of Pinus radiata only on Quercus agrifolia near Monterey, Palo Alto and Menlo Park, California. Near the latter two places col- lections were also made by Mr. J. T. McMurphy. Pinus radiata in its natural range occurs only in an extremely limited area on the coast, but is planted extensively. Quercus agrifolia is common along the coast from Mendocino south, but does not even penetrate into the great valleys of the Sacramento and San Joaquin Rivers, much less into the Sierra Nevada, where Peridermium harknessii, so-called, is very common on Pinus sabiniana, P. ponderosa and P.jeffreyi, and above all, on P. contorta. In the regions inhabited by these pines other oaks, particularly Quercus californica and Castanopsis chrysophylla are common, both of which Hedg- cock has successfully inoculated with aeciospores of Peridermium cerebrum. It is, therefore, still possible, that Quercus californica and Castanopsis chrysophylla or perhaps some of the other associated oaks, may be the alternate hosts of the so-called Peridermium harknessii on some of the Sierra Nevada pines. Farlow and Seymour (p. 161) name Pinus ponder- osa as a host for Peridermium cerebrum Pk. However, no Cronartium has been found, to the writer's knowledge, on Quercus californica or Cas- tanopsis chrysophylla in California. Cronartium Quercuum is by no means common on Quercus agrifolia in the vicinity of Pinus radiata. In fact, one may say without exaggera- tion, that there seems to be no direct relation between the distance of oak from infected pines and the frequency of the Cronartium, even where the oak is standing close to heavily infected pines. Never very abundant, it is found as common on oaks standing isolated or one hundred to two 4 Shear, C. L. Peridermium cerebrum Peck and Cronartium Quercuum (Berk.) Journ. Myc. 12: 89. 1906. 6 Arthur, J. C. North American Flora, 72: 122. 6 Hedgcock, G. G. and Long, W. H. Identity of Peridermium fusiforme with Peridermium cerebrum. Journ. Agr. Res. 2: 247. 1914. 1916] MEINECKE: PERIDERMIUM AND CRONARTIUM 227 FIG. 1. Gall of Peridermium harknessii on Pinus radiata with aecium. Result of direct aecial infection. Note the sharp line of demarcation at the basal end and the incipient witches'-broom formation in connection with the gall. 228 PHYTOPATHOLOGY [VOL. 6 hundred yards and more from the nearest pines as on those in closest proximity to Peridermium galls. In the midst of an unusually heavy infection of Peridermium it is not uncommon to find the oaks immediately FIG. 2. Typical older gall of Peridermium harknessii on Pinus radiata from type locality. The aecia are confluent but not typically cerebroid. adjoining infected pines quite free from Cronartium. In many cases where old, richly sporulating galls stand within a foot of the nearest oak branches, so close that in a heavy wind they must necessarily touch each other, the oak leaves were found to be without a sign of Cronartium. 1916] MEINECKE: PERIDERMIUM AND CRONARTIUM 229 The infection of the oak leaves is not heavier in the lee of pines with richly sporulating galls than in other sites, although here, close to the ocean, the prevailing winds are very constant. The very uneven dis- tribution of the fungus on Quercus agrifolia may find its explanation in racial characteristics and susceptibilities of the oak. The telial form on Quercus agrifolia is even less frequent than the uredenial form. The writer has found the latter locally plentiful on Quercus densiflora and Quercus chrysolepis along the Coast to the Oregon line, always with- out the telial form. On the * Klamath River in the northwestern part of California near the coast the writer collected a uredenial form on Quercus chrysolepis, which caused a distinct witches'-broom. Possi- bly this is a new form; the formation of witches'-brooms, it seems, has never been observed in other uredinial infections on oak. Another Cronartium received through the courtesy of Messrs. J. T. McMurphy and J. W. Sheldon was collected in the middle of May in the Coast Range near Palo Alto, California on Quercus durata. Quercus durata is an ever- green shrub. The collection comes from a region where Peridermium harknessii is common on Pinus attenuata and P. radiata. Whether any of these pines occurred in the immediate vicinity of the infected oaks is not known. Hedgcock7 was successful in infecting several California oaks (Quercus lobata, Q. densiflora, Q. calif ornica) and also Castanopsis chrysophylla with aeciospores from Peridermium cerebrum. His inoculations of two pines, Pinus ponder osa and P. murrayana (contorta), which are common bearers of the so-called Peridermium harknessii in California, with telio- spores, supposedly from Quercus rubra, produced typical galls of Peri- dermium cerebrum. On the other hand, his inoculations of oaks with material of Peridermium harknessii on Pinus radiata from California, failed. In 1912 Hedgcock8 again reports that "repeated and careful inocula- tion with aeciospores of this Peridermium (P. harknessii) on the leaves of young oaks of a number of species failed to infect them, while at the same time, inoculation with Peridermium cerebrum Peck on the same species of oak trees brought about an infection, resulting in the uredinia and telia of Cronartium Quercuum (Brond.) Arth." The possibility that these failures were due to loss of viability of the spores in transit prompted the writer repeatedly to try inoculations with fresh material on Quercus agrifolia and Q. californica. All these attempts were without success. 7 Notes on Peridermium cerebrum Peck and Peridermium harknessii Moore. Phytopath. 1:131. 1911. 8 Mycologia 4: 143. 230 PHYTOPATHOLOGY [VOL. 6 Strong as are the reasons for assuming that Peridermium harknessii is identical with Peridermium cerebrum, there are well-founded considera- tions which make it imperative that the connection should actually be proved by inoculation. One of these is the apparent independence of Cronartium Quercuum and Peridermium harknessii. Another is the dif- ference in appearance. The aecia of Peridermium harknessii, at least on Pinus radiata, are not typically cerebroid (fig. 2) ; they usually appear as separate sori and the rather delicate peridium breaks open very soon after coming up through the bark. A comparison of figure 2 and Hedg- cock and Long's photographs (their plate XI) show the difference very plainly. More important is the apparent rarity in our Peridermium of pycnia exuding "abundantly a yellowish, sweet fluid" as on Peridermium cerebrum,* which are also mentioned by Shear.10 In spite of diligent search the writer has only once succeeded in finding pycnia of Peridermium harknessii on a young gall on Pinus jeffreyi in early spring (April) . The pycnia contained very small pycnospores and did not break through the bark. In the literature the writer does not find any other reference to pycnia on Peridermium harknessii. To these distinctions may be added the fact that in infections with Peridermium harknessii, particularly on Pinus radiata, P. contorta and P. attenuata, witches'-brooms are extremely common and that the galls very often continue to fruit for many years, both of which phenomena are rare in Peridermium cerebrum according to Hedgcock.11 It is well to remember also, that all the numerous and careful attempts at infection of Quercus agrifolia with aeciospores of Peridermium harknessii have failed. The typically spindle-shaped form (Peridermium fusiforme) which has recently been proved by Arthur and Kern12 and by Hedgcock and Long (I.e.) to be identical with Peridermium cerebrum, apparently does not exist on the Pacific Coast or at least is very rare. The typical gall of Peridermium harknessii is always very well defined; the transition from stem to gall is never gradual, but always very abrupt. When the infection takes place in 1- and 2-years-old twigs, the swelling generally embraces the whole stem ; in the next year these galls often take the shape of a pear, with the thick part downwards, and later become spherical. On a little older stems the swelling may be one-sided and later develop into a hemisphere. But whatever form the gall takes, it is always very clearly set off against the un thickened stem; this is particularly noticeable 9 Mycologia 4: 132. 10 Jour. Myc. 12: 91. 11 Mycologia 4: 143. 52 Arthur, J. C. and Kern, F. D. North American species of Peridermium on pine. Mycologia 6: 135. 1914. 1916] MEINECKE: PERIDERMIUM AND CRONARTIUM 231 on the basal end of the gall, whilst the swelling at the apical end of very young galls is sometimes more gradual. Whether these distinctions are sufficiently important to separate the two forms can only be decided by inoculations. Possibly most of them may be explained by the specific influence of the host. The actual proof for the identity of the two forms is still lacking, although Arthur and Kern13 now list Peridermium harknessii under P. cerebrum. For all the pines growing in association with oaks, it is to be assumed that the connecting Cronartium form may still be discovered. One species of pine that does not enter into this system is Pinus contorta, a tree which in the Sierra Nevada inhabits higher elevations and is particularly common around and on mountain meadows. Although frequently found associated with oaks or Castanopsis, it often occurs in localities sixty to eighty miles and more from the nearest representative of either genus. The infection of Pinus contorta with Peridermium harknessii is no less common in such areas, in fact, in some localities it reaches an extraordinarily high degree. Macroscopically the fungus is identical with Peridermium harknessii on Pinus radiata. It is true, that there are data to be found in the literature regarding great distances that certain spores are able to travel without losing their faculty of infection. Klebahn14 cites a case in which spruce plants were infected by sporidia of Chrysomyxa Rhododendri from Rhododendron plants over a distance of 6 kilometers (v. Tubeuf) and quotes Thaxter as follows: "although it has been shown that infection from cedars may take place at a dis- tance of eight miles (Gymnosporangium nidus-avis)." In both these cases, conclusive proofs for which it would undoubtedly be difficult to bring, the small and light sporidia are said to have traveled a long dis- tance; in our case the fungus would have to be carried, by means of the large and heavy aeciospores, from pine to oak or Castanopsis for sixty to eighty miles over mountains and flat country, more or less covered by a thick screen of forest trees, and back again the same distance by means of sporidia. In the case of Pinus murrayana in the Northwest this distance must be figured by hundreds of miles. The question arises as to the means by which the fungus spreads. Either this fungus on Pinus contorta connects with an unknown alternate host or it is identical with the Peridermium harknessii of Pinus radiata. In this case it must be more or less independent of the supposed alter- nate stage on oaks or Castanopsis and its heteroecism is not obligate. The absence of oaks and Castanopsis in many Pinus contorta stands, the relative rarity of Cronartium Quercuum on Quercus agrifolia even in 13Mycologia6: 133. 14 Klebahn. Die wirtswechselnden Rostpilze. pp. 32-33. 232 PHYTOPATHOLOGY [VOL. 6 the immediate vicinity of heavily infected Pinus radiata and its apparent absence on oaks and Castanopsis of the Sierra Nevada suggests the pos- sibility that infection of what we call Peridermium harknessii on Cali- fornia pines may take place directly from pine to pine by means of aecio- spores. This, of course, does not exclude the possibility of infection by sporidia, where Cronartium on oaks is present. The idea in itself is not a new one. Eriksson,15 in discussing the prob- able mode of dissemination of Peridermium Pini, for which no alternate host was known, came to the conclusion, without adducing any proof however, that infection must take place directly from tree to tree. Kle- bahn (pp. 40 and 380) on the other side considers the formation of aecia of heteroecious fungi from aeciospores or spermatia as a priori improbable. Mentioning Eriksson's failure to report a successful outcome of his direct inoculation experiments he even goes so far as to say "Es kann also hiernach auch als ziemlich sicher angenommen werden, dass eine Infektion der Kiefer mittels der Aecidiosporen nicht moglich ist." Hedgcock, accord- ing to recent personal information, has tried direct inoculation with nega- tive results. EXPERIMENTATION In the following, the results of the writer's experiments are given. The aecial material used was collected on the morning of May 22, 1913 from richly sporulating galls of typical Peridermium harknessii on Pinus radiata at Sausalito, Marin County, California, where the fungus is very common, but where in spite of the most careful and continued search no Cronartium could be found on the native Quercus agrifolia. Other oaks or Castanopsis do not occur in the vicinity. The material was kept dry and taken at once to San Francisco, California (a distance of a few miles only). The plants used for the inoculation experiments consisted of a series of four young trees of Pinus radiata (3-years-old) in pots, from a reliable nursery. They were about two to two and one-half feet high, in perfect health, thrifty and without a sign of Peridermium. We will designate them as I, II, III and IV. They were kept in the labora- tory, in the center of San Francisco, where contamination from the out- side is out of the question and where there existed no possibility of in- fection through sporidia from Cronartium on oak. On May 22 and May 23, 1913, No. I was inoculated in seven places of different ages with aeciospores suspended in water, by wounding the sprayed bark with a sterilized needle and gently rubbing the infection ]5 Eriksson, J. Einige Beobachtungen iiber den stammbewohnenden Kiefern- blasenrost, seine Natur und Erscheinungsweise. Centralbl. Bact. II Abt. 2: 385. 1896. 1916] MEINECKE: PERIDERMIUM AND CRONARTIUM 233 material into the wounds. Two of the wounds were left open, not ban- daged. The others were wrapped in cotton and paper or protected by paper bags. The bandage was left on for a number of days. The wrap- ping made it necessary to cut off the bundles of needles in the neighbor- hood of the wounds. No. II was treated on May 23, 1913 in a number of places without wounding. The places chosen for inoculation were sprayed before and after the application of the spores. Here also the needles were cut. In other places dry spore material was dusted on after cutting the impeding needles and spraying. A sporulating gall was tied to a twig. All inoculations were protected by paper bags. All inoculated places were marked with colored twine. Ill and IV were not inoculated. Ill was allowed to stand in a room together with I and II. IV was kept in a separate room. A prolonged absence made regular inspections impossible. The plants, however, were sprayed regularly. In December of 1913 several distinct oblong swellings, suggestive of Peridermium harknessii galls, were discovered on tree No. I on places inoculated in May. No. II also seemed to show a swelling in one place. This plant, however, soon began to decline and finally died. Immediately above the swellings on the younger parts of the living plant adventive buds began to sprout in the characteristic manner of witches'- broom formation so commonly observed above the galls of Peridermium harknessii. The other two plants of Pinus radiata remained in perfect health as did all other parts of the inoculated plant. Even No. Ill, which had been standing close to the infected plants for more than seven months showed no sign of infection. > During the winter of 1913-1914 the swellings, which had now become so typical that in nature one would without hesitation classify them as young galls of Peridermium harknessii, remained more or less stationary. No signs of pycnia or of aecia were apparent. The risk of losing the plants in the unfavorable conditions of a city laboratory made it advisable to transfer the trees to the open. On March 12, 1914 the remaining plants, Nos. I, III and IV were planted close together in the experimental gar- den of the Campus of the University of California, Berkeley, California. All through the year of 1914 the swellings were more or less stationary; the witches'-brooms became, if anything, a little more distinct. No signs of pycnia or aecia appeared. An inspection on March 3, 1915 brought the final result. The swellings on No. I had increased somewhat in size; the witches'-broom formation was very plain. Aecia had broken out, in each case in the very point of inoculation, indicated by a slight depression. The photograph (figure 1) shows plainly the gall, with the aecium, and the beginning witches'-broom formation above. 234 PHYTOPATHOLOGY [VOL. 6 The inspection of the infected trees on March 25, 1915 gave the follow- ing results: Of the seven inoculations on tree No. I five had taken, four of which had produced well-defined aecia; two of these, on one-year twigs, pro- duced slender barrel-shaped swellings, encircling the entire twig (one with an aecial row, about 7.5 mm. long, in the axis of the swelling; the other without an aecium, resin drops present in several places). Of the re- maining three infections, one is represented by the photograph (figure 1) ; the swelling is of slender barrel shape. The aecium measures 1| by 3 mm.; the swelling itself measures 3 em. in length by 1.2 cm. in diameter as against 0.6 cm. of the stem immediately below. Another infection caused a gall to form around about one-half of the circumference of the stem; it bears a large aecium in the center. The third infection on the lower part of the stem (at least 3 years old) resulting in a gall about three- fourths around the circumference, has a small aecium in the center. The exact ages of the stem and twigs at the various places of infection could not be determined because the plant was kept for further observations. As to the two unsuccessful inoculations, it will be remembered that in two cases the spore material had not been protected by cotton and paper and had probably dried up. The control plants III and IV were in perfect health without a sign of Peridermium harknessii. All parts of plant I not inoculated remained sound. At the present time (December, 1915) the galls have grown considerably; the check plants and all not inoculated parts of tree I are perfectly sound. The period of incubation as figured from the time of inoculation to the first manifestation of the effect of infection, in this case, of the swelling, must be about four to five months. The first appearance of aecia in the experiments took place about twenty months after inoculation. In nature, the first swelling appears in the fall of the year of infection. Dur- ing the next year the young gall remains stationary or grows but little. In the spring of the third year, the aecia develop and sporulation begins. In the experiments the one-, two- and three-years-old stems and twigs proved susceptible to infection; none were made on twigs younger than one year, because at the time of experimentation the buds had not yet sprouted sufficiently. In nature, infection of stems older than two years must be rare, at least no infection on older stems could be found in spite of careful examination of the great number of galls. Infection of twigs during their first year of growth, on the other hand, is frequent. Investi- gations of this kind must, of course, be made in spring, because the result of spring infection begins to show towards fall of the same year. 1916] MEINECKE: PERIDERMIUM AND CRONARTIUM 235 Examination of the galls produced in the experiments shows that the aecia and the aeciospores are typical for Peridermium harknessii. Arthur16 records under Cronartium Quercus (Brondeau) Schroet. 17 to 23 by 25 to 32ju for aeciospores on non-Californian pines. Arthur and Kern17 give 15 to 21 by 23 to 31ju for Peridermium harknessii and 17 to 23 by 25 to 32/z for Peridermium cerebrum. Later they18 gave 15 to 24 by 23 to 33/z for Peridermium cerebrum, in which they now in- clude Peridermium harknessii. The measurements of the aeciospores of Peridermium harknessii resulting from direct aecial infection in our experiments are as follows: (148) 11 to 26/z by 19 to 41/t (standard 17 to 22 by 24 to Fresh material of Peridermium harknessii collected on Pinus radiata at the type locality near Monterey, California, measures: (50) 11 to 24/z by 22 to 37/z (17 to 20^ by 26 to 30ju). For comparison with these values the following measurements of aecio- spores of Peridermium harknessii on various hosts including the two for- mulas given above may be of interest: Pinus contorta (Rocky Mountains). (50) 15-24 x 19-43 (17-19 x 22-26)M. (50) 15-24 x 20-37 (19-20 x 22-26)/i. (50) 17-26 x 19-28 (19-22 x 20-26)^. Pinus contorta (Sierra Nevada). (50) 13-22 x 19-33 (17-19 x 22-24)M. (50) 15-26 x 20-37 (17-20 x 22-26)ju. (50) 13-22 x 17-30 (15-19 x 22-26)/i. (50) 11-24 x 19-35 (17-20 x 22-26);*. (50) 15-26 x 19-31 (19-22 x 22-26)0. (100) 13-30 x 19-33 (17-22 x 22-28)^. Pinus jeffreyi. (40) 13-26 x 17-33 (17-20 x 20-26)/*. Pinus ponder osa. (40) 11-22 x 20-35 (17-22 x 26-30)/*. (50) 15-24 x 16-37 (17-20 x 24r-30)/i. '• North Am. Fl. 72:122. 17 Arthur, J. C. and Kern, F. D. North American species of Peridermium. Bui. Torr. Bot. Club 33: 421 and 423. 18Mycologia 6: 134. 19 (148) gives the number of spores measured, then follow the extreme values and finally in parenthesis the standard values. See Meinecke, E. P., Spore measure- ments. Science, n.s., 42: 430. 1915. 236 PHYTOPATHOLOGY [VOL. 6 Pinus radiata. (50) 11-24 x 22-37 (17-20 x 26-30)/*. Pinus radiata (aecial infection). (148) 11-26 x 19-41 (17-22 x 24-30);*. Pinus attenuata. (28) 19-30 x 26-41 (20-22 x 26-30)/z. Pinus sabiniana. (50) 15-24 x 20-37 (17-20 x 26-30)M. Pinus virginiana (eastern form). (50) 15-24 x 22-37 (19-22 x 26-31)M. The values for the extreme measurements in this list vary so much that a composite formula would read: 11 to 30 by 16 to 43/z. It is plain that the extremes cannot be used for comparison. If we consider the standard values only, it appears that the widths vary very little from the values 17 to 22 //. The lengths, however, permit us to distinguish two well-defined groups, one wth the values 22 to 26 /* and another with the values 26 to 30 /z. The slight variations from these values lie well within the unavoidable margin of error in measuring and in rounding off the figures obtained. The first group includes all the specimens on Pinus contorta (murrayana from the Rocky Mountains), P. contorta (Sierra Nevada), and P. jeffreyi, that is, high elevation forms; the second group, the material from Pinus ponderosa, P. sabiniana, and P. radiata, that is, forms from the middle and lower slopes of the Sierra Nevada and from the coast little above sea level. To the latter group must be added Peridermium cerebrum from Pinus virginiana. Fur- ther inoculation experiments will have to decide the question whether or not these groups actually correspond to two different fungi. Obviously too great an importance must not be accorded to spore measurements unless they are well supported by other structural and biological char- acters. Morphologically all the aeciospores examined resemble each other very closely. On the other hand, the remarkable regularity of standard values as shown, for instance, in nine specimens from Pinus contorta on the basis of five hundred measurements, suggests the use- fulness of such spore measurements for purposes of identification. That our material from Pinus contorta has nothing to do with Peridermium filamentosum which is very common in the same localities, is shown by a comparison with the formula for aeciospores of the latter fungus (numerical basis 100) : (100) 17-39 x 22-78 (22-26 x 30-33)/*. The fact that the standard values for Peridermium cerebrum on Pinus virginiana are practically the same as those for P. harknessii on Pinus 1916] MEINECKE: PERIDERMIUM AND CRONARTIUM 237 radiata, P. ponderosa, P. attenuate,, and P. sabiniana furnishes new evi- dence for the assumption that the two forms on the hosts named are identical, without, of course, proving it. FACULTATIVE HETEROECISM OF PERIDERMIUM HARKNESSII The experiments prove that Peridermium harknessii is able to infect at least Pinus radiata directly by aeciospores, that is, with omission of the telial stage, if there is any. In other words, although it is highly probable that the fungus is heteroecious, this heteroecism must be facul- tative. The same is very probably true for the so-called Peridermium harknessii on Pinus attenuata and P. contorta and perhaps for that on the rest of the Sierra Nevada species of pines. Haack20 published — one year after the writer began his experiments, and, of course, independently — positively results of direct aecial inocula- tion of Peridermium Pini on Pinus sylvestris. His first experiments were inconclusive; he, therefore, later inoculated pines already heavily infected, reasoning that these individuals would be more susceptible to the disease. This latter procedure together with the fact that he operated entirely in the open, already infected forest, makes his otherwise valuable experiments inconclusive. The results of my inoculations of Pinus radiata with Peridermium harknessii lend a strong support to the outcome of Haack's experiments. Like others before him, Haack suspected that wounding of the bark is a prerequisite for successful inoculation and assumes that insects are largely responsible for such injuries. Hedgcock21 states that "in nature, young Peridermium galls are often found associated with wounds made by an insect." On older parts of the tree the fungus "may gain entrance through wounds made by birds (sapsuckers), but this hypothesis remains to be proven." All the writer's observations go to show that insects play an impor- tant, if not a decisive, role at least in direct aecial infection of the fungus from pine to pine. The common presence of old wounds in connection with Peridermium harknessii galls and the type of distribution of the galls on the individual tree as well as on a group of trees speak against promiscuous infection from a shower of wind-borne spores. When the infection is not general, the galls are usually found only up to a certain relative height, depending on the height and crown development of the 20 Haack. Der Kienzopf (Peridermium pini (Willd.) Kleb.) Seine tTbertragung von Kiefer zu Kiefer ohne Zwischenwirt. Zeitschr. Forst- und Jagdw. 46: 3-46. 1914. 21 Phytopath. 1: 132. 238 PHYTOPATHOLOGY [VOL. 6 tree and of the group of trees of which it is a part. In one of the examples given in the introduction to this paper, only five galls out of a total of 173 were over five feet from the ground. In another case only about twenty out of 529 were found above six feet from the ground. Often they are found only on one side of the tree or the group, unevenly dis- tributed. Since we must assume that at the time of spore dissemination all the young twigs and branches are equally susceptible to infection, a shower of spores would find equal conditions for germination and pene- tration of the bark, at least in a majority of twigs or branches, and the infections would be more evenly distributed over the crown. The fact that in our experiments inoculation with wounding was successful in five out of seven cases and gave only one very doubtful result in the unwounded tree which subsequently died, speaks for the intervention of insects in nature. All other causes of wounds through which infection could take place are absent in the case of Pinus radiata and P. attenuata. The winters of their habitat are very mild; the summers too cool for sun-scorch. Light- ning and hail are practically unknown. The common occurrence of spittle-bugs (Aphrophora sp.) on young stems and twigs of Pinus radiata may have some significance. During spring, that is, at the very time when the galls of Peridermium harknessii are in full sporulation, the writer found them profusely .at Monterey, California, throughout the very heavily infected stands. The larvae of this cercopid wound the young stem by puncturing it. Provided the spittle contains no ingredients harmful to the aeciospores caught in it, the latter would find ideal conditions for germination by being kept moist for a considerable time. When the spittle dries up they would auto- matically be drawn onto the fresh wound made by the insect. It is to be noted that the spittle-bugs are nearly always located on young stems and twigs which are still protected by needles. The writer's inoculations show that not only the youngest stems, but also at least three-years-old ones may be artificially infected. In nature this is rare; so are spittle- bugs on three-years-old stems. Hedgcock and Long22 find that the swellings of Peridermium fusiforme "on the three-needle pines often originate near the extremity of a branch, and, as the side branches develop, the fungus invades them, producing an enlargement of the base of each branch." Pinus radiata is a three- needle pine and similar enlargements of the base of each branch of a whorl are not uncommon. Spittle-bugs very often are located on the whorl at the base of the branches. 22 Jour. Agr. Res. 2: 248. 1916] MEINECKE: PERIDERMIUM AND CRONARTIUM 239 FACULTATIVE HETEROECISM OF CRONARTIUM QUERCUUM Recent inspections of oaks of the infected area on the Monterey penin- sula disclosed an apparent parallelism between the facultative nature of the heteroecism of Peridermium harknessii and that of Cronartium Quer- cuum. The relative scarcity of the latter in the immediate vicinity of the former has already been pointed out. At the time of the first obser- vation (first half of April) no Cronartium in its telial form had developed, but uredinial sori were fairly common on young leaves and more frequent on old green ones. The leaves of Quercus agrifolia remain living and green on the tree throughout winter and often until late in spring. On last year's green leaves fresh urediniospores came forth more or less abundantly from the old Cronartium spots, generally in a circle im- mediately around the dark-brown, dead, sunken-in places occupied last year by the Cronartium. The mycelium of the fungus, therefore, evi- dently overwinters in the leaf and produces urediniospores in the follow- ing spring, which are able in their turn to infect the young sprouting leaves. Hedgcock23 has successfully inoculated Quercus lobata, Q. cali- fornica and Castanopsis chrysophylla with urediniospores from Quercus rubra. It is, of course, not impossible that some of the uredinial sori on the young leaves were the results of infection from aeciospores from Peridermium harknessii on Pinus radiata. The numerical relation of these sori to the old ones, however, speaks for an infection through ure- diniospores rather than through aeciospores from Peridermium harknessii, at least early in the season. Later infection from Peridermium may be- come more plentiful. Inspection of the same stands in the beginning of May did not disclose an increase in sori. The sporulation (uredo) on young leaves had all but stopped. No telial stage was found. The old green leaves were still on the trees, but sporulation on these had stopped altogether. The Cronartium on another evergreen oak, Quercus durata, mentioned above, seems to behave in a similar manner. Here the uredinial sori were not very numerous on last year's leaves and were distinctly rare on this year's foliage, which was about one-third developed. The sori are smaller than on Quercus agrifolia, but here again the old sori produced urediniospores in quantities. The urediniospores are rather large. Oc- casionally very small telial columns were found; it was impossible to decide whether these were the product of last year or recently formed. This uredinial infection explains the occurrence of Cronartim Quercuum in apparent independence of a heavy infection of Peridermium harknessii. The heteroecism of the Californian Cronartium Quercuum seems to be facultative as is that of Peridermium harknessii on Pinus radiata. 23Phytopath. 1: 131. 240 PHYTOPATHOLOGY [VOL. 6 SUMMARY Although not definitely proved, it is highly probable that Peridermium harknessii is identical with P. cerebrum. In California Peridermium harknessii and Cronartium Quercuum are to a high degree independent of each other. The so-called Peridermium harknessii can be transmitted directly from pine to pine by infection with aeciospores, at least on Pinus radiata; in nature this probably takes place through the agency of insecte. The heteroecism of Peridermium harknessii on Pinus radiata is, therefore, facultative. By analogy it is highly probable that the same facultative heteroecism occurs in Pinus contorta and perhaps also in the other hosts of the so-called Peridermium harknessii. Cronartium Quercuum overwinters on Quercus agrifolia; new uredinio- spores form in spring around the old, dead sori on old living leaves and infect the young leaves. The heteroecism of the Cronartium also is facultative. OFFICE OF INVESTIGATIONS IN FOREST PATHOLOGY BUREAU OF PLANT INDUSTRY SAN FRANCISCO, CALIFORNIA • UNIVERSITY OF CALIFORNIA LIBRARY