Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. 2 ren 7 U. S. DEPARTMENT OF AGRICULTURE. BUREAU OF PLANT INDUSTRY— BULLETIN No. 63. B, T. GALLOWAY, Chief of Bureau. INVESTIGATIONS OF RUSTS. BY MARK ALFRED CARLETON, CEREALIST IN CHARGE OF CEREAL INVESTIGATIONS. VEGETABLE PATHOLOGICAL AND PHYSIOLOGICAL INVESTIGATIONS. Issurp JuLy 12, 1904. rh Drea EHS, Tilsen 2 = = OF | t 6 fe < e' CS 0 ( i fl 5 3 sone . A =i Naan ‘ We = ALA WASHINGTON: GOVERNMENT PRINTING OFFICE. 1904. - BULLETINS OF THE BUREAU OF PLANT INDUSTRY. The Bureau of Plant Industry, which was organized July 1, 1901, includes Vege- | table Pathological and Physiological Investigations, Botanical Investigations and Experiments, Grass and Forage Plant Investigations, Pomological Investigations, and | Experimental Gardens and Grounds, all of which were formerly separate Divisions, | - and also Seed and Plant Introduction and Distribution, the Arlington Experimental | _ Farm, Tea Culture Investigations, and Domestic Sugar Investigations. : Beginning with the date of organization of the Bureau, the several series of bulle-- _ tins of the various Divisions were discontinued, and all are now published as-one | series of the Bureau. A list of the bulletins issued in the present series follows. Attention is directed to the fact that ‘‘the serial, scientific, and technical publica- | tions of the United States Department of Agriculture are not for general distribution. All copies not required for official use are by law turned over to the Superintendent of Documents, who is empowered to sell them at cost.’’ All applications for such publications should, therefore, be made to the Superintendent of Documents, Govy- | ernment Printing Office, Washington, D. C. No. 1. The Relation of Lime and Magnesia to Plant Growth. 1901. Price, 10 cents. 2. Spermatogenesis and Fecundation of Zamia. 1901. Price, 20 cents. 3. Macaroni Wheats. 1901. Price, 20 cents. 4. Range Improvement in Arizona. 1902. Price, 10 cents. 5. Seeds and Plants Imported. Inventory No. 9._ 1902. Price, 10 cents. 6. A List of American Varieties of Peppers. 1902. Price, 10 cents. — 7. The Algerian Durum Wheats. 1902. Price, 15 cents. 8. A Collection of Fungi Prepared for Distribution. 1902. Price, 10 cents. 9. The North American Species of Spartina. 1902. Price, 10 cents. 10. Records of Seed Distribution and Cooperativ e Experiments with Grasses and - Forage Plants. 1902. Price, 10 cents. 11. Johnson Grass. 1902. Price, 10 cents. 12. Stock Ranges of Northwestern California. 1902. Price, 15 cents. 13. Experiments in Range Improvement in Central Texas. 1902. Price, 10 | cents. 3 as 14. The Decay of Timber and Methods of Preventing It. 1902. Price, 55 cents. | 15. Forage Conditions on the Northern Border of the Great Basin. 1902. Price, 15 cents. 16. A Preliminary Study of the Germination of the Spores of Agaricus Campes- tris and Other Basidiomycetous Fungi. 1902. Price, 10 cents. | 17. Some Diseases of the Cowpea. 1902. Price, 10 cents. 18.” Observations on the Mosaic Disease of Tobacco. 1902. Price, 15 cents. 19. Kentucky Bluegrass Seed. 1902. Price, 10 cents. 20. Manufacture of Semolina and Macaroni. 1902. Price, 15 cents. 21. List of American Varieties of Vegetables. _1903. Price, 35 cents. 22. Injurious Effects of Premature Pollination. 1902. Price, 10 cents. 23. Berseem. 1902. Price, 15 cents. . 24. Unfermented Grape Must. 1902. Price, 10 cents. 25. Miscellaneous Papers. [. The Seeds of Rescue Grassand Chess. II. Saragoila Wheat. III. Plant Introduction Notes from South Africa. IV. Congres- sional Seed.and Plant Distribution Circulars, 1902-1903. 1903. Price, 15 cents. {Continued on page 3 of cover.] Bul. 63, Bureau of Plant Industry, U. S. Dept. of Agriculture. PLATE.-1. | A PERENNIAL RUST. (AACIDIUM TUBERCULATUM E.& K.ON CALLIRRHOE INVOLUCRATA GR.) US DEPARGMENT OF AGRICULTURE. BUREAU OF PLANT INDUSTRY— BULLETIN No. 63. B. T. GALLOWAY, Chief of Bureau. INVESTIGATIONS OF RUSTS. BY MARK ALFRED CARLETON, CEREALIST IN CHARGE OF CEREAL INVESTIGATIONS. VEGERABICh.PATH@ LOGICAL AND PENS l@ LO GLC Aue INVESTIGATIONS. IssuED JuLy 12, 1904. WASHINGTON: GOVERNMENT PRINTING OFFICH. 1904. BUREAU OF PLANT INDUSTRY. Be: GALLOWAY, Chief. J. E. RockweEt., Editor. VEGETABLE PATHOLOGICAL AND PHYSIOLOGICAL INVESTIGATIONS. SCIENTIFIC STAFF. ALBERT F. Woops, Pathologist and Physiologist. Erwin F. Smitru, Pathologist in Charge of Laboratory of Plant Pathology. — GEORGE T. Moore, Physiologist in Charge of Laboratory of Plant Physiology. Hersert J. WEBBER, Physiologist in Charge of Laboratory of Plant Breeding. Water T. SwineLe, Physiologist in Charge of Laboratory of Plant Life History. Newton B. Prerce, Pathologist in Charge of Pacific Coast Laboratory. M. B. Warre, Pathologist in Charge of Investigations of Diseases of Orchard Fruits. Mark ALFRED CARLETON, Cerealist in Charge of Cereal Investigations. HERMANN VON SCHRENK,@ Jn Charge of Mississippi Valley Laboratory. P. H. Rours, Pathologist in Charge of Subtropical Laboratory. C. O. TownsEenD, Pathologist in Charge of Sugar Beet Investigations. P. H. Dorserr, Pathologist. . Ropney H. True,? Physiologist. T. H. Kearney, Physiologist, Plant Breeding. Cornetius L. SHEAR, Pathologist. Wixuram A. Orton, Pathologist. W. M. Scorr, Pathologist. JOSEPH S. CHAMBERLAIN, Physiological Chemist, Cereal Investigations. R. E. B. McKenney, Physiologist. Fiora W. Patterson, Mycologist. CuarLes P. Hartiey, Assistant in Physiology, Plant Breeding. Karu F. Ke_iermMan, Assistant in Physiology. DEANE B. SwinGie, Assistant in Pathology. A. W. Epson, Scientific Assistant, Plant Breeding. JESSE B. Norton, Assistant in Physiology, Plant Breeding. James B. Rorer, Assistant in Pathology. Luoyp 8. Tenny, Assistant in Pathology. GrorRGE G. HepGcocKk, Assistant in Pathology. PERLEY SPAULDING, Scientific Assistant. P. J. O'Gara, Scientific Assistant. A. D. SHAMEL, Scientific Assistant, Plant Breeding. T. RatpH Rospinson, Scientific Assistant, Plant Physiology. FLORENCE HeEpGEs, Scientific ‘Assistant, Bacteriology. CHARLES J. Branp, Scientific Assistant in Physiology, Plant Life History. a Detailed to the Bureau of Forestry. b Detailed to Botanical Investigations and Experiments. bo BIDEN. (QE TRONS IDEN TANG. U. 5. DrepartMenT oF AGRICULTURE, BurEAv oF Puant INpusTrRyY, OFFICE OF THE CHIEF, Washington, D. C., April 20, 1904. Str: I have the honor to transmit herewith the manuscript of a technical paper entitled ‘‘ Investigations of Rusts,” by Mark Alfred Carleton, Cerealist in Charge of Cereal Investigations, Vegetable Pathological and Physiological Investigations, and recommend its publication as Bulletin No. 63 of the series of this Bureau. The two illustrations accompanying the manuscript are necessary to a complete understanding of the subject-matter of this paper. Respectfully, B. T. GaLLoway, | Chief of Bureau. | Hon. JAMES WILson, Secretary of Agriculture. elk Te esaC Je. The experiments and observations on rusts which are the basis of the following notes were begun by Mr. Carleton several years ago, and were continued at intervals until the spring of 1900,when the pressure of other duties prevented further work of this kind up to the present time. The results obtained in many instances are still incomplete, but are of sufficient value to be recorded. Some of the species studied are of much economic importance. The investigation is a continuation of the work reported in Bulletin 16 of the Division of Vegetable Physiology and Pathology, and is concerned chiefly with the segregation of rust forms of economic importance on the common grasses and the completion of the life history of certain species. The work is to be carried on more extensively during 1904. A. F. Woops, Pathologist and Physiologist. OFFICE OF VEGETABLE PATHOLOGICAL AND | -PHystoLocicaL INVESTIGATIONS, Washington, D. C., March 26, 1904. +) CON TENSES; Page NGGiiiOnspLOLouruiKnowled@erotslile Inistonieses 5 4c ee Se eee ee ) Hmplocolasnusts( Cromuyecesseupnorbien Cand ies) 1). aa eee ee ee 9 SHIMON PUSS (CANeCIMNIG MAomUuOn SO ive) 2525 25 a2 eee eae Boo ees dst Crownexust, OL oats eLuccimiamhamnt(peerss|) \Wiettsts se o- 5.22 ee nee 13 SEOne SALOME ObAMNOS biol ann tS ae home Mee hares ene ae ee tok Myce iON ear cet ar NE Vat te 14 black steminushor-A cro pyromeamd EH linmisieerseee ee e ye reee e 15 Orance leat rust or Acropyrompamde bya Use ye ee ny eae ity PlAckIStemMenUs tO gTOStiseclod VULO MRIS Sars see eae fee pe ey ee 17 USt Oi Cinlonis GReccinianeloniGis) ICES) see eke oe ee ee et 18 Rusts of willow and cottonwood (Melampsora)...:.....-..----./-4----- 18 Wainer resis tancexOleulne unedOi se epeseess 2 oe ee Nee ee eee ie es eae ke 1) Uredo of Kentucky bluegrass rust (Puccinia poarum Niels.) .-.-.-------- 20 Wredo.ok Puccwna montanensis Will: {= oo neue eae 20 BML OCMC NMAC aOUAUIONS oe Me rucege ou ulema te eee Ata ca a tle oi 9 eg 2 UC CUNUCE CH COUS( HEUTE A ea tamu me bore ne cca eM lua nr abcie xe tee RY Mea oF pan ae 22 Experiments with Lepto-uredinee. ---- ee Sepa ater oinlee (are Gh SE eT NS 25 uUsiOlcocklepurs(uccinia canthty SChiw. ens 2.255 co 5 es ee ee 26 ust olmvelvet leat CPuccinia leterospora iB. and/@.)-= 222-222 222 | 26 Rene MMi sme Clesetee: cunt Le ape iene Seeman ta See all ee ig he ee Oy PANO MR QEO CH CULLCHUU IID Ween TN Cl ay aoe Spec) Ss Pee te a 27 VIS ROME CU GCCLONUNUATOCMUGULCGO UII saci Sa 1 eh Tee ee 28 DESC EIOME Op plate seem ney Ne oie ence ee age lal I ee ee Be 32 ILLUS TRATIONS: Page. Bere OA perennial RUSt a2 pee ee Bee Sans 2 eee eee Frontispiece. II. Rusts of Euphorbia and grama grass.......-------- Be ees eee 4, Go2e eae B. P. I.—102. VaR. Pe aize INVESTIGATIONS OF RUSTS. ADDITIONS TO OUR KNOWLEDGE OF LIFE HISTORIES. In many instances, without any experimental proof, it is inferred that there is a connection between the different forms of rust occur- ring on the same host plant simply because of their constant associa- tion with each other. Sometimes it is afterwards demonstrated that these inferences are wrong, though they are probably correct in a majority of cases. Studies of the following species were made with the view of obtaining a more accurate knowledge of their life history. EKurnorsia Rust ( Uromyces euphorbix C. AND P.). Until the experiments herein described were performed it had not been demonstrated that there is any connection between the ecidial and other stages of this species, although experience naturally leads one to think that there is. They are in very close association on the same plant, the ecidium appearing first, quickly followed by the uredospores. In the spring of 1893 Mr. J. B.S. Norton, now pro- fessor of botany at the Maryland Agricultural College, while engaged ‘in experiments in the germination of weeds in the greenhouses of the Agricultural Experiment Station at Manhattan, Kans., called the writer’s attention to avery young rusted seedling of Huphorbia dentata. In this instance, as is usually the case with the young plants of this host, the pods were first badly affected by wcidia. This fact, taken together with the common observation that the seed pods of this host are usually affected by all stages of the rust, led at once to the thought that it was a case of rust propagation through the medium of the germi- nating seed of the host, something not before demonstrated for any other species in the entire group of Uredinee, so far as the writer knows, unless we except the single instance of the experiments of Doctor Eriksson” with Puccinia glumarum.’ The seed used by Mr. @Vie latente et plasmatique de certaines Urédinées. Compt. Rend., 1897, pp. 475-477. 6T. 8S. Ralph, in Victorian Naturalist, Vol. VII, p. 18, describes an instance of a rust attacking the seed of Senecio vulgaris, stating that ‘‘with the microscope we are able to trace the fine yellow sporular matter into the covering of the seed, and into _ the seed itscli;”? but apparently it was not determined by further investigation whether or not the rust was able to reproduce itself through the germinating seed. 9 10 INVESTIGATIONS OF RUSTS. Norton was examined and the pods were found to be badly affected. Moreover, he stated that the seeds were planted without shelling. But the writer did not know then, as he does now, that this fact would probably make little difference, since the naked seeds are commonly affected, often showing actual peridia. To test the theory of rust propagation above mentioned, experiments were instituted on April 22 for growing plants from rusted seed under a bell jar. The seed used bore all stages of the rust. The experiments were in five series: (1) Seeds shelled and disinfected by mercuric chlorid; (2) seeds unshelled and disinfected: (8) seeds shelled, but not disinfected; (4) seeds unshelled, not disinfected; (5) like series No. 4, but rusted mainly with ecidium. All were planted in pots in a ereenhouse and the pots were kept under bell jars. On May 1 the plants began to come up. After about three months, when the plants had grown to a height of 3 to 5 inches, no rust had appeared on series 1 and 2, and only one spot on one plant of series 3. The plants of series 4 and 5 were much rusted, the ecidium appearing first, fol- lowed shortly by uredosori. On April 25, 1893, it was attempted to germinate teleutospores of rust from the seeds used in these experiments, in water-drop cultures, which resulted in failure. On June 28, 1893, a similar culture of the fresh uredospores failed to germinate in two days. In 1895 rusted seeds of Auphorbia dentata, sent from Kansas, were planted in the greenhouse of the Department of Agriculture, at Wash- ington, D. C. From these three plants grew, which were kept under a bell jar. Soon one of these plants rusted badly, first with the ecid- ium, then a slight amount of the uredospores, and later the teleuto- spores. It should be remarked here that Euphorbia rust, so far as reported, occurs only on /. maculata in the vicinity of Washington, D. C., and the writer has never yet been able to obtain rusted seeds in that region. On December 11, 1896, a third series of experiments was started at Washington, D. C. On that date rusted seeds of Auphorbia dentata from Kingman and Manhattan, Kans., were planted and kept under a bell jaras before. Eleven plants resulted by December 26. On March 8, 1897, spermogonia appeared in considerable amount on the young leaves of one plant, with a tendency to form a sort of hexenbesen. On March 29 two more plants were rusted, one with spermogonia only on the young leaves, and the other with ecidia on the fruit. On April 10 still another plant showed spermogonia, making four in all, out of the eleven, that became rusted. (See Pi. I, fig. 1.) As above stated, the proof that the rust actually penetrates the hulled seed is readily obtained, not only from microscopical demonstration, but also from the fact that the actual peridia may often be seen with the unaided eye in the seed. These experiments, however, further SUNFLOWER RUST. ileal demonstrate the ability of the rust to propagate itself through the medium of the germinating seed of the host, and also make it seem probable that this is even the common method of reproduction in the case of its occurrence on Huphorbia dentata. It will be noted also that the results of these experiments make it almost certain that the Atcidium and Uromyces appearing upon the plants are one and the same species, since in every case all stages resulted from planting the rusted seeds, the ecidium appearing first, then the uredo, and then the teleutospores. If anything was lacking, however, the proot has since been made complete by the experiments of Dr. J. C. Arthur, as reported in the Botanical Gazette,¢ in which the uredospores and teleutospores were obtained on Huphorbia nutans from a sowing of eecidiospores from other plants of the same host on June 20, 1899. As is well known, the Euphorbia rust is widely distributed over the United States, occurring on numerous host species, but it is probably most abundant on 4. dentata and /. preslii. It is a significant fact, bearing upon the ontogeny of the species, that it is also on these two hosts, particularly on /. dentata, that the secidium is most common, and that the rust attacks the seed so severely. The seed pods are also affected considerably in the cases of /. data and /. marginata. On June 12, 1897, ecidiospores of this rust had germinated very well in water-drop culture after three days, and on June 22, after a two days’ culture in water of both the ecidium and uredo from Euphorbia marginata, the latter germinated sparingly, but the former not at all. In no instance could the teleutospores be germinated, though germination was not attempted very often. ~The writer has collected all three stages of this rust on Huphorbia naculata, L. marginata, E. dentata, FE. preslii, E. glyptosperma, and Y. heterophylla. On F. petaloidea and FE. serpyllifolia only the uredo and teleuto stages were found, and on /. data and what was probably ty. geyert even the uredo was rarely seen. SUNFLOWER Rust (Puccinia helianthi Scuw.). Although Saccardo rightly regards this species of Schweinitz as quite distinct, and includes with it the Avcidium often associated on the same host, in many herbaria the authority of Winter and Burrill is followed in making it a form of Puccinia tanacet?, while the Atcidium is commonly referred to Accdiwm compositarum, a convenient dump- ing ground for numerous uncertain forms. The writer has always considered this disposition of the species to be without any good reason even on a purely morphological basis, and now the experiments dArthur, J. C., ‘‘Cultures of Uredinez in 1899,’’ Bot. Gaz., Vol. X XIX, No. 4, pp. 270-271, April, 1900. 19 INVESTIGATIONS OF RUSTS. here recorded make it rather certain that Schweinitz and Saccardo are correct. So far as this country is concerned, the writer is convinced that 2. tanaceti either belongs almost entirely to tanacetum or does not exist at all. So far it has been utterly impossible, even in a green- house, to make transfers of the uredo from one to another of the numerous supposed hosts of that species, except among. hosts of the same genus.“ It is,at any rate, pretty certain that the forms occurring on Vernonia, Helianthus, Actinella, and Aplopappus, which have been referred to 7. tanaceti at various times, should be considered distinct. The circumstances connected with the culture experiments with this _ species were in themselves peculiar. Late in the autumn of 1897 at Manhattan, Kans., it was desired to obtain fresh material of the uredo for inoculating various hosts, but at that date very little else than the teleuto stage could be found. Finally, on October 29 a small amount was found on //elianthus petiolaris, mixed among a much larger quan- tity of teleutospores, and from this material sowings were made on //. petiolaris and /T. annuus. On November 8 there resulted one rust spot on the latter host and three on the former. The spots were of the uredo stage, but the interesting feature accompanying this culture was the appearance first of spermogonia in one of the spots. This fact made it probable thata part of the infection resulted from the teleuto- spores of the inoculating material, even at this unusual season for the germination of these spores. On March 7, 1898, while stationed at the University of Nebraska, inoculations of //. petiolaris were again made with the teleutospores only from other plants of the same host, from which numerous spermogonia appeared in eight days, followed shortly by ecidia, which were fully developed by November 1. By these results the connection of the different stages of the rust is pretty well established. At the same time it is shown that the forms on I. petiolaris and /7. annuus are identical. In all cultures made of this rust both the uredospores and teleutospores have been found to germinate easily and produce infections readily. Reverse cultures with ecidiospores were not made. kare These experiments were first reported at the 1900 meeting of the Society for Plant Morphology and Physiology, at Baltimore. Since that time Drs. J. C. Arthur? and W. A. Kellerman’ have made a number of such experiments, confirming these results, but also seem- ing to indicate a distinction of host forms on different species of sun- «Dr. M. Voronin at first also obtained negative results in similar experiments in Russia in attempting transfers of the rust on to other hosts. (See Bot. Zeitung, vol. 30, pp. 694-698, Sept. 27, 1872.) Later he obtained infections of Puccinia tanaceti from Tanacetum vulgare on sunflower, which, however, did not produce such vigorous growth as ordinarily. (Bot. Zeitung, vol. 33, pp. 340,341, May 14, 1875. ) » Botanical Gazette, vol. 35, p. 17, January, 1903; Journal of Mycology, vol. 10, pp. 12-15, January, 1904. : : ¢ Journal of Mycology, vol. 9, pp. 230-222, December, 1903. ow et Se CROWN RUST OF OATS. 1183 flower. Doctor Voronin, in his experiments above mentioned, also found that rust of cultivated sunflower would not infect L/elcanthus tuberosus. In 1901 Ernst Jacky @ inoculated the following hosts with teleutospores from //elianthus annuus: H. annuus, Hl. cucumerifolius, HT. californicus, H. tuberosus, Il. maxiniliana, H. multiflorus, L. scaberimus, and H. rigidus, with resulting infections of the three first- named species, but no infection of any of the others. The evidence from all these experiments just quoted and those of the writer shows at least that the rusts of MJelcanthus annwus (includ- ing cultivated varieties), 77. petcolaris, and //. mollis are identical, with the probability that a distinct form exists on //. tubcrosus. Sunflower rust has been collected by the writer on the following species of Helianthus, including all stages on nearly every species: TL. annuus (both wild and cultivated), ZZ. rigidus, H. petiolaris, H. tuberosus, IT. hirsutus, H. manimiliana, IL. grosse-serratus, H. orgyatis, LH. mollis, and /T. ciliaris. The ecidium occurs rarely in compari- son with the occurrence of other stages, but is to be found on a num- ber of hosts and occasionally in considerable abundance. This rarity of its occurrence, together with the occurrence of spermogonia so often with the uredo, may be accounted for by the fact that the uredo is often produced by direct teleutosporic infection. Crown Rust oF Oats (Puccinia rhamni |PErs.| Werrtst.). In a.mere note ina previous bulletin of this Department? it is stated that certain infections had just been. made showing the connection of the crown rust of oats on Phalaris caroliniana and Arrhenatherum elatius with the ecidial form on Rhamnus lanceolata. No other dem- onstration of such a connection of forms had been reported up to that time. During the same season, however, Doctor Arthur obtained infections with the ecidium of Rhamnus lanceolata on oats at Lafayette, Ind.“ The experiments of the writer are here given in detail. On August 23, 1897, the uredo stage of a rust, supposed to be Puc- cinia coronata, was found in great abundance on Phalaris caroliniana at Stillwater, Okla. This host, with the rust, was transferred to a green- house of the Agricultural College at Manhattan, Kans., and inocula- tions were made on oats, wheat, and orchard grass on August 30, 1897, resulting September 7 in a good infection of oats, a poor one of the orchard grass, and no infection at all of wheat. Other inoculations were made September 1 on wheat and rye, with no result. By October 8 the teleutospores had appeared on the original plants of Phalaris @Centralb. Bakt. Parasit. u. Infekt., 2 Abt., Bd. 9, No. 21, pp. 802-804, December, 1902. © Cereal Rusts of the United States, Bul. No. 16, Div. of Veg. Phys. and Path., U.S. Dept. of Agriculture, 1899. ¢ Bul. Lab, Nat. Hist. State Univ. Iowa, Vol. IV, pp. 398-400, December, 1898. 14 INVESTIGATIONS OF RUSTS. at Stillwater and were of the crown rust type. After this date the experiments were continued at the State University laboratories at Lincoln, Nebr., all host plants then in use being transferred to that place. On November 16 the crown rust was found, in the uredo stage, on Arrhenatherum elatius on the State University farm, and a rusted plant was transferred to the greenhouse. On December 11 inoculations with the rust were made on oats and rye, resulting in a good infection of the former in twelve days, but with no result on the latter. Fur- ther inoculations of oats with the Phalaris rust on February 16, 1898, resulted again in a good infection in 9 days. Nospecies of Rhamnus is native near Lincoln, Nebr., but Rhamnus lanceolata 1s rather common at Weeping Water, about 20 miles east of Lincoln, where it is often badly rusted with A¢cidium. From that place a large amount of the Acidium was obtained fresh on June 1, 1898. A water-drop culture of the material, made the next day, gave a profuse germination of the spores in twenty-two hours. Inocula- tions with the ecidiospores on oats and Phalaris caroliniana were made June 1 and June 2, resulting in a successful infection of Phalaris on June 14 and of oats on June 18. The oat inoculations were made simply on detached portions of the plant preserved with their broken ends in water in a damp chamber. As in all other instances, these inoculations were made with the greatest of care to prevent accidental infections. The whole series of experiments proves (1) the connection of the ecidial form of Rhamnus with the crown rust of oats, and (2) the identity of the latter with the forms on Phalaris caroliniana and Arrhenatherum elatius, besides making it probable that orchard grass may also support this species. SEGREGATION OF HOST PLANTS. The most important economic results of the study of rusts are likely to be derived from the investigation of the relationship of the forms on our common grasses. Such work has already been carried on to some extent by the writer and partially reported in the builetin entitled ‘“Cereal Rusts of the United States.” A more detailed account of some of this work will be given here. Because bearing upon the same question, it seems proper to mention also some experiments with the rusts of Salix and Populus. Probably the greatest confusion exists concerning the identity of the different forms on Agropyron and Elymus, though there is much uncertainty also about those occurring on Bromus and other genera. The experiments here described were conducted at Stillwater, Okla.. Manhattan, Kans., Lincoln, Nebr., and Washington, D. C., the host plants being sometimes transferred from one place to another. Of all these rusts the one receiving most attention was the black stem rust of Agropyron and Elymus. PO its iste riley BLACK STEM RUST OF AGROPYRON AND ELYMUS. 15) Biackx Stem Rust or AGROPYRON AND ELYMUS. At least three and probably four different rusts occur on the species of these two grass genera, and are often so closely associated that their accurate identification is extremely difficult. Of the herbarium specimens of these rusts throughout the country, probably not one in fifty is identified with any certainty. The writer’s experiments with these forms are still incomplete, but a few things at least have been established. When these grasses are brought under cultivation the changed conditions and proximity to other grasses and grains cause them to become much more rusted than is ordinarily the case. In the cultivated grass plats at the experiment stations in Oklahoma, Kansas, and Nebraska the rusts were found in great abundance. It was therefore easy to carry on many culture experiments. These experiments with the uredospores of black stem rust were sufficiently numerous to make it desirable to arrange them in the following table: Tasie I.—Culture experiments with black stem rust of Agropyron and Elymus. Period Date. Locality. Pre NC necuane Plant inoculated. cue Result. in days. ena, OS 7/ oa ass Washing: Cones Coal Wale a ter =ne eases ele Elymus virginicus.... 10 | Success. IDOesseowasulieacs CW tee acasenseallsacac WOR eerie ase WANN as soe oSouascaee 10 Do. Veins PA MeO Se slesses GOSS RIC Seep eR Be CG) REC oe oe eee Elymus virginicus.... iat Do. IDOsassosssalsaces ClO Sea seeosor Sass lO es ay See eee Agropyron richard- IG Do. soni. DOS seen Usces GO eginncsa sense Rieter GORraaetwestenietsisice Wilt'e athens aa erste 11 Do. DORs a leoehas GOCE A Eager aa: COR seee. Seen sl nopuron occidentale 11 | Failure. Sept. 13, 1897 ...| Stillwater, Okla -..| Agropyrontenerum...| Wheat...............- 6 | Success. @ ID) Oe ne toes es MOR e a: aalew fee Gon Save HU Agropyron tenerum . 6 Do. Ocoee: Manhattan, Kans .| Agropyron occidentale| Wheat............--- 12 | Failure. Dowie et les: COP ee uN Ria Wheat (originally: |2o32: COs REL Gi oa See 8 | Success. Agropyrontenerum). Dose soon lesene ORE Sess ee hes Se COREA err oa. Barleyer anes scene eae 8 | (6) IDO eee ees GOR es ee ee GORE eee ee Agropyron tenerum .. 8 | Failure. c Oe, ZL MY Se cellasoue (Gh a Sao Ae Ones amos COS ASA eeses Wiebe: ances ee ee 16 | Success. DOPE Se ee alana (GG es es ee hs es ee COE Sse eee Isthaleee ee Geneon ease 16 Do. IDO Re Soanods a aeee ClO Soa oedaae ae ace GOmsesseces ess OSs shes c een 16 | (a) IDO sees aul mesa COR eae siee OU ash aie Sa RViCl Asean are tee eee 16 | Failure. DORR Ss same a eae GOSi eee eee Agr opt yronioccidentale | Wiheatsa-s5-..+2.-2-- 18 Do ADoser ello oes GOs Arson ler Ol Omar ca cere. IRVieten eee neers 18 Do Doses ee sees CLO RR doen pe ake ae Seay atte SA AIMS BELG Var ion ee 18 | Do. IDO Seaeeeeae lasaee GO messes ne re ie aks Oe es ee Agropyron tenerum .. 18 | Do. INOVe2418972-—-| nin colm. Nebr as. on| ss... CKO ee ee Agropyron occidentale 15 | Success. Ven Ue ceAsilocod ClO ae cea asiae Elymus canadensis’ Wheat. 22.22.22. 22.2 21 Do. e | glauctfolius. DOF eee CO eee re eae ClO Raa Se tees ae IB ATIC Veneta eee ZAG Do. Vewn PA Wes se ouilaseos GOR eames: Wiheatw.(orieinalllys |awWiheatsen sets. ince. 10 Do. Elymus canadensis glaucifolius). DOR eee Se QO se ae | ae (OKO as Gen er ee IB Tews nt es 10 | Do. He best 898s Eee GOmtest es eeSe Elymus. canadensis |) Wheatss-52222.5..2.- 14 | Do.f | glaucifolius. | IDO aetestaolaeeee CKO) Rasen so Ee AS eas 8 CONS ee oe IBATIO We peeiteswon Se 14 | Do. DORs eens GOR eE pees a see (ClO) GaSe SAE SERS oes Vi Cue etioe aaa eee 14 | Failure. IDO SHR Aeecs aoe GORE S tee bal eae OO Sas ub eeueeeee Oats issn acne 14 | Do. IDO SSeS oneal aes ClO Soa soaeeetia nee GORGES eS ae Elymus canadensis 14 | Success. glaucifolius. Dot tees | Pits COE ete ae? eke Clone sake Aes ies Elymus virginicus.... 14 | Failure. DORs aa ese tee GOGS sseece eee alee kOe UG omnes 5 aie Elymus virginicus 14 Do. muticus. Do sees ee ClO casaeee easels sae GOR esi R age se se Elymus intermedius. . ae Do. DOXA Reeees | eee ClO aaa ese lemenas COs tee eee Agropyron tenerum .. 14 | Do. DO, been eee ClO pa seats ee chee GOES ee ated Agropyron occiden- 14| Do. tale. } aPustules differ in color from the original. d Apparently 1 pustule formed. b1 pustule only. e Rust changes color and form of pustule. ¢ Conditions very unfavorable, however. f Rust changes color. 16 INVESTIGATIONS OF RUSTS. TaBiE 1.—Culture experiments with black stem rust of Agropyron and Elymus—Continued. | | | Period Date. Locality. Origin Lh ewe Plant inoculation, eee Result. in days. | Feb. 11, 1898.---| Lincoln, Nebr..--- Elymus virginicus.... Elymus virginicus. --.| 13 | Suecess. IDO wee oracles (OKO eh Sa erage ee CG LOM Rea Stn ae Elymus virginicus 13 Do. muticus. DY es eee COs seater sles CO eee ee | Elymus canadensis 13 Do. glaucifolius. 1 DOs Sas Ses Het aie CO} Aes eee does Sees | Agropyrontenerum... iS Do. Doses. Ieee (lope seers asa |saae Ore een Agropyron occiden- 13 | Failure. : taieé. | - 1) Ones a eee dO 8 een lessee CO acces eee oe RES ac oie sree 13 Do. Nowe so fpettes do;.. Se eee [iaeeee Gorse re eae faWhenteac 6 ae eee 13 Do. Hebr 211898. 2.5.2. 2 QOS eee ee | Wheat (originally | Elymus canadensis. . 7 | Suceess. a Elymus canadensis | glaucifolius). Weby2a yl S98 sass | ae OO ie ena ner eae MO ease oso =| LOT GCUNU JUDGED aaa Tat Do. HMEDSZS 1898 ess Stans Oe eee ee | Elymus CANAAENStsS | Weal as esse eae 9 Do.b glaucifolius. a Pustules differ in color from the original. bRust changes in appearance. The results of these xpennien es considered in connection with those recorded in Bulletin No. 16, Division of Vegetable Physiology and Pathology, U. 8. Depeamhen: of Agriculture, appear to establish two things, viz, (1) that the forms of black stem rust on wheat, barley, Hordeum jubatum, Agropyron tenerum, A. richardsoni, Hlymus cana- densis, and EF. canadensis glaucifolius are identical, with the proba- bility that those on Elymus virginicus, E. virginicus muticus, and FHlolcus lanatus® should be included; (2) that the black stem rust of Agropyron occidentale? is physiologically distinct from any other.‘ A very interesting phenomenon in these experiments was the change in color and form of sorus of the rust produced by a transference to another host. In some cases after a transfer the rust was scarcely recog- nized. The change of color was sometimes from a bright yellow toa deep brown or orange, or the reverse. The uredo of Agropyron tene- rum, for example, was often very yellow on the leaves, but changed to brown when transferred to wheat. On the species of Elymus the rust has a brown, waxy appearance, and the teleutospores long remain cov- ered by the epidermis of the host. «On January 5, 1900, quite successful infections on wheat were made with the uredospores of black stem rust of this host. b Probably the most correct name of this host, which is known also as Agropyron spicatum and A. glaucui (See Hitchcock, ‘‘Note on Nomenclature,’’ Science, vol. 17, pp. 827-828, May 22, _403.) ¢The form on this host was described asa distinct species, named Puccinia agropyri, by Ellis and Everhart, in Journal of Mycology, Vol. VII, p. 131, March 10, 1892, a fact not noticed by the writer until after most of these experiments were made. This species includes Acidium clematidis D. C. according to Doctor Dietel, the proof of relationship being the result of culture experiments. (Oesterr. Bot. Zeitschr., No. 8, 1892.) Bae sh ca | ORANGE LEAF RUST OF AGROPYRON AND ELYMUS. it ORANGE LEAF Rust oF AGROPYRON AND ELYMUS. In the following table are summarized the results of inoculations with the uredoform of this rust. They were carried on simultaneously with those of the black stem rust, and the material was taken chiefly from the same individual host plants. Tasue Il.—Culture experiments with orange leaf rust of Agropyron and Eyres. Period Date. Locality. Clee poeuane Plant inoculated. ous Result. in days.) . sot | : IDSOsA UEC coolt Wels ona von, IDE Oca! Ne sccugesaeascunonae Elymus americanus - - . 16°} Failure. WDiole sssSeee Sneee GOSS sce ssee: Mace Oost Vee eee sect 16 | Success. Teas 7 eye sehellesane GOAL esa Sealers GLO RRS ees ere | Elymus virginicus. ---| 12 | Failure. Wotee sore k. GO esses soc os eciee GONE iets Se 'setis RViGi Ss she ne seers | 12 | Success. ICO tL, Me Gosoqlsaass CORES eee ne te GOs ae ees: Elymus virginicus....| 13 | Failure. IWORsensones lngece GlOR Se Se eee os ame ee GOS eee are ce IRAVi Ges tan arate es 13 | Success. Heels lS 97x mane eae COW sarees WihGatiass stxcncsnae.s Agropyron richard- | 18 | Failure. sont. DOanseacedalscode ClO mane aa acenes cose QO ceasbsqacesnees Wihleal beer retcieee iene | 18 | Success. IDO Re teeee cele oeee doness.: Han Beal ese ClO) Gace at aeebey UV Cn Games eaweyeeree 18 | Failure. REDS ADS Meh esaclacsan CO ees a REN Ce ese Agropyron tenerum. - - 12 Do. IDO Sssecosna lanes GOES Stee eee Clos aeeaaeascnas Triticum villosum ....| 12 Do. IDOeSoaces aoa) Gas 00). ae Se eeameleeaae GO ee Elymus canadensis ..- 2, Do. DORR ene lessee GOs te oe aecl eoeies COM os eerste IB Gac aee seoue caer ames 12 | Success. Wiehe, BU) eM eae|lbocoe COLON aenates demerarl aeeee (ClO Anes COA a ese Agropyron caninum. . 26 | Failure. DOkeer A rarleeees GO et es eae GOR ee ae See Bi: EAC ieee Sik Ss Se eens 26 | Success. Nov. 3, 1897 ....| Manhattan, Kans..|....- C0). AE ae oonBee VWWhn@ ate sete Sa sear ae 9 | Failure. DOeeee sacle sac GOs seer eer earns GOjasse ees sees Bare yess see ascass 9 Do. DORE Me seen asee ClO) eee Eeoadoenbisooae Gow neana ae Agropyron tenerum. 9 Do. IDs ates ee lars GOp eae el | ere KOS Me Se me cast RAV Meee Sete eet eta ers 9 | Success. Vain, B, US Jess) IIANCOA ING Oe ssseellesoos (ClO) E annette rea bere ne CORSSE eee eee 21 Do. IDOSSsaaocan iaeece CLO) eye ans es ere COE ah ae tinsoe Elymus virginicus ...- 21 | Failure. Wier; 40 NS eSalleooas dobsta IPM RUS CORGHVECUS casall \WIDENS sacasoneoonusd- 18 Do. Woe esata Genes QOS esse soe: Elymus canadensis |....- CUO eee Semen rete 18 Do. glaucifolius. Wile, WA NE} ce slicoaae GOs Soo Pheer NANO ERS rie Sere alge CO aoa aes Bas 14 | Success. 1) Ones ea eee CORR IS eA aa eee QO eee ee Elymus canadensis -.. 14 | Failure. ID Osea ears | aoe GOR Se Se sasece lease GOS ieicens sense Elymus canadensis 14 Do. glaucifolius. IDOg areas Sea oe ClO Riss eee naleagee GOMar eee Saetee See Agropyron tenerum. .- 14 Do. The chief conclusion to be derived from the results of these cultures is that the orange leaf rust is very sharply limited in its host adap- tation and differs widely in this respect from the black stem rust. Similar results are given in Bulletin No. 16 of the Division of Vege- table Physiology and Pathology, U. S$. Department of Agriculture, for cultures of the forms on wheat and rye. In fact, it is quite proba- ble that almost every distinct host species bears a distinct form of the rust. One of these forms on “lymus virginicus L. has recently been found by Doctor Arthur to be connected with the Atcidium on /inpa- teens aurea Mubl. and is now to be known as Puccinia impatientis (Schw.) Arth. # Buack Stem Rust or AGROSTIS ALBA VULGARIS. Culture experiments with the uredoform of this rust and observa- tions in the field indicate that it is distinct and does not occur on other « Botanical Gazette, vol. 35, pp. 18-19, January, 1903. 27787—No. 63—04——2 18 INVESTIGATIONS OF RUSTS. hosts.“ The results of the culture experiments are given in the follow- ing table: TaBLe II1.—Culture experiments with black stem rust of Agrostis alba vulgaris. | | Period Date. Locality. OH iob eeu arNe Plant inoculated. pees Result. in days Dec. 238, 1897-..| Lincoln, Nebr ..... Agrostis alba vulgaris.| Agrostis alba vulgaris. 8 | Success. ID Oa Ganetease secne GOys- Ae seer oea|loeeee GOR te ace Wiheaite: tse5- tear 8 | Failure. Qe eel sen ee GOR. ae eee ne GOR a eee es Osist see oe es oe 8 Do Vamene 4 1898 ses |eaeac GORn sa oa2 eee eee GO ee eee Ss Wil eater niet 12 Do IDO sSaeadae |saoue Ona esas ae | ee GO ee eee | OatsS oo = eee 12 Do. Hebe ldlS98ss5 |e =- GOREeSR Estee Elymus canadensis | Agrostis albavulgaris.) 14 Do. glaucifolius. | The rust is evidently of the black stem rust group (Puccinia graminis of authors), but contains quite a number of abnormal teleutospores, including mesospores. Many measurements of these spores average 27-54 by 16-23, mostly 40-46 by 16-18. Rust oF Cuuioris (Puccinia chloridis DIET.). The uredoform of this rust is sometimes very abundant on Chloris verticillata in the Great Plains region, occurring in late summer and autumn. ‘The sori are deep brown in color. The uredospores germi- nate very freely and easily. In a number of experiments made in 1898 it was found that the uredo on C. werticillata and C. elegans would readily transfer from either host to the other, but not to other grasses, in several cases which were attempted. In a watch-glass cul- ture, made March 18, 1898, of uredospores from C. elegans, produced from artificial infection in a greenhouse, not only these spores germi- nated freely, but a number of newly formed teleutospores at the same time, an occurrence unusual except in the Lepto-uredinee. Among thousands of cultures made by the writer only one other instance of this kind has occurred. In the summer of 1895 at the Biological Lab- oratory at Cold Spring Harbor, Long Island, both teleutospores and uredospores taken from the same sorus of a rust on Luzula campestris gave good germinations.? Rusts oF WILLow AND CoTTronwoop (MELAMPSORA). Both the uredospores and teleutospores of the rusts of willow and cottonwood germinate readily, the germ tubes of the latter containing always brilliant endochrome. Healthy leaves of either cottonwood or willow placed in a damp chamber have often been infected by the « Arthur describes culture experiments made by his assistant, William Stuart, in July, 1898, in which wheat plants were infected with uredospores from this host, but the spores of the infection sori were larger than those of the original material. (Bul. Lab. Nat. Hist. State Univ. Iowa, vol. 4, No. 4, pp. 396-397, 1898.) >The species was, without much doubt, Puccinia obscura Schroet. WINTER RESISTANCE OF THE UREDO. 19 writer in nine to twelve days. The incubation period is much short- ened by using germinating spores in the inoculations. In the month of October, at Manhattan, Kans., an infection was produced in this way in three days. It was attempted by numerous inoculations with the uredoform, chiefly at Washington, D. C., to transfer the rust from willow to cot- tonwood and the reverse, but always without success. An interesting feature of these experiments was the discovery of the fact that the cottonwood most common in Washington, known as South Carolina poplar, could not be infected by the uredoform from the common Western cottonwood, though these two poplars are classed by some as being the same species. Moreover, the rust does not occur in nature on the South Carolina poplar, but is very abundant on the Western - cottonwood, and even occurs in Washington on the few individual trees of that type growing in the city. WINTER RESISTANCE OF THE UREDO. In another bulletin’ the writer has given in detail the observations and culture experiments proving the successful wintering of the uredo in the orange leaf rust of both wheat and rye. In this connection it is easy to see a number of closely correlated facts, which may mutually explain each other: (1) As shown under the preceding topic, the uredo of black stem rust may infect a number of different hosts, and there- fore has a manifoldly greater chance of propagation with the same number of uredospores than if there were but one possible host; (2) as also shown, the uredo of orange leaf rust is restricted in every case to but one host, or at most to but one genus, and a much greater produc- tion of uredospores is therefore necessary for the life of the species in this stage; (8) as a corresponding matter of fact it is well known that the uredo of the latter rust exists usually in very much larger quantity than that of the former; (4) on the other hand, the teleuto- sporic stage is the prevailing form of the stem rust, which fact makes this rust usually the more damaging of the two, as the teleutospores infest the stem chiefly, thus more directly interfering in plant nutri- tion; (5) the stem rust is proved to be connected with the barberry rust, thus giving it an additional chance for increased propagation, and this through the medium of the teleuto stage instead of the uredo; (6) finally, the uredo being the prevailing form of the leaf rust, and no ecidial form being known in this country,? it would seem necessary that this stage of that rust should be very hardy in order to endure extremes of cold and drought and preserve the life of the species. Previous investigations of the writer and others have amply proved that this is the case. In the meantime it is found that in other species “Cereal Rusts of the United States, Bul. 16, Div. Veg. Phys. and Path., U.S. Dept. of Agriculture, pp. 21-23, and 44, 45. > Except in the case of the form on Elymus virginicus already mentioned, 20 INVESTIGATIONS OF RUSTS. there exists a similar hardiness of the uredo, of which cases the fol- lowing will be discussed here: Urepo oF Kentucky BiurGrRaAss Rust (/uccinia poarum NYELS.). The writer has known for some time that the uredo stage of the blue- grass rust is able to pass the winter alive and in germinating condition during any season as far north as Lincoln, Nebr., but additional evi- dence has been obtained from time to time. At the same time it issig- nificant that there is no record that the teleutospores have ever been _ found, except in one instance, at the above-named place. In fact, few, if any, uredoforms so hardy as this one exist in this country. On February 1, 1893, this uredo was still alive in the vicinity of Man- hattan, Kans. Every month of the year it exists alive and growing in great abundance everywhere about Washington, D.C. On March 2, 1898, it was found fresh on green leaves of the host at Lincoln, Nebr. On the same spot of ground it was still growing and spreading rapidly on May 8 of the same year. Host plants were transplanted that day into a greenhouse, where the rust continued to increase rapidly. As would now be supposed, the rust is sharply limited to its one host, Kentucky bluegrass. The results of the following cultures may be given In evidence. 3 TABLE 1V.—Culture experiments with the uredo of Kentucky bluegrass. ; Period | Be ee Origin of inoculat- | : ae se oy of incu- Date. Locality. ing eaetiericll Plant inoculated. pation Result. be days.| Jan. 16,1893....| Manhattan, Kans .| Poa pratensis ........ Wiheaitietss saa | 18 | Failure. IDOB2cegcsse JoasoK0O= oouansessses|bsoee JOS eee eneeree OMNIS as sesescscdo5asc5| 18 | Do. Dec. 21, 1896..-.| Washington, D.C..| Rye (Uredo rubigo- | Poa pratensis ........ 16 | Do. vera). | | Dame 2 18972 ss 5)a- cae dO siescinn fees Wheat (Uredo gra- |....- Oe asee eee 11 | Do. mints). DO BRAS aatee eae Oia: seep see tees oe Gees seeere eames Poa nemoralis.....--- 11 | Do. Hebei S97 eas hace (c (ORE raeet m Rye (Uredo rubigo- | Poa pratensis ...-.-.--| 13 | Do. vera). | DOe ane eee|= sees COs a Ss apes 6 KO pe eee aes Poa nemoralis.....-.. | 13 Do. Mebslssi897s22.|- = GO ren ease eees Wheat ( Uredorubigo- | Poa pratensis ...-.---| 18 | Do vera). IRE O, As ISS oa lsesee GO sera: sot ee IANO NROFADSIS. S66 50505|Q5056 Ce Kove mis ere ll 8 10 | Success UREDO OF PUCCINIA MONTANENSIS ELL. This is, in some respects, one of the most interesting of grass rusts. It is one of the ‘* covered rusts,” and is, indeed, so far covered that it is often entirely overlooked by collectors. The uredosori are very uniform in size and are exceedingly small, it being necessary often to examine them, or even find them, with a hand lens. They are ellip- tical in shape and placed end to end in long, narrow, yellow striz between the veins of the leaf. The teleuto stage is so far hidden as to be detected only by a faintly darker color beneath the leaf epi- dermis. The rust is the most nearly ike P. glwmarum Eriks, and EMERGENCY ADAPTATIONS. ill Henn. yet found in this country. The known hosts are Elymus cana- densis and LE. virginicus, but it seems to occur on other hosts. Whether the forms on different hosts can be transferred from one to another is not yet fully determined. The important fact now known, however, is that the uredoform is able to preserve the species over the winter without the intervention of other stages, though it is possible that extensive propagation is aided by other stages. October 28, 1897, fresh uredosori were observed on Hlymus canadensis at Manhattan, Kans., and again in the same locality on November 2. But as early in the spring as May 26, at Lincoln Nebr., when there was yet but a small beginning of vegetation, the uredo had burst the epidermis of the host in grass plats at the University farm. Previous to this the living uredo had been observed in these plats practically every month of the winter. In other instances the uredospores of certain species are so very abundant and the teleutospores so rare that there seems a probability that such species are carried over from summer to summer largely through the uredo stage alone, though there is no absolute proof of such a course. ‘Two instances are particularly interesting—those of the uredos of Puccinia cryptandri Ell. and Barth., and Puccinia on Panicum autumnale.¢ The uredospores of these species begin to be conspicuously abundant about midsummer, but continue in consider- able abundance until very late in autumn. The uredo of Pandcum autumnale was found in germinating condition in Kansas up to Novem- ber 3 in 1897. A water-drop culture of uredospores of this species gave excellent germination In ten hours August 21, 1897, at Perkins, Okla. The uredospores of Puccinia cryptandri were found in extreme abundance in Oklahoma until October 11, 1897, but in all cases with- out any accompanying teleutospores. Often the uredosori had a fresh appearance on portions of leaves that were quite dead. EMERGENCY ADAPTATIONS. In connection with some culture experiments conducted at Lincoln, Nebr., in the botanical laboratory of the State University, in February, 1898, a water-drop culture was made (February 3) of uredospores of the above-mentioned Puccinia cryptandri which had been collected on October 8, 1897, at Perkins, Okla., and kept to date as herbarium specimens. A fair germination resulted in twenty-four hours. Spores from the same collection were used on February 16 to inoculate seed- lings of Sporobolus avroides,’ with the result of the appearance of two rust spots by March 16. These spots may really have appeared much earlier and been overlooked, as they were very small and the host @ Perhaps a new species, needing further study. b Apparently this same species of rust had already been collected on Sporobolus airoides in the same locality where the collection from S. cryptandri was made. 22 INVESTIGATIONS OF RUSTS. itself is well known to have extremely narrow leaves. Moreover, the spores were not germinated when applied, and, being from dried speci- mens, the incubation period would naturally be long. Seedlings of S. cryptandri were not at the time available. On March 16 a second water-drop culture was made from this dried material, resulting in the germination of a few spores. Teleutospores from herbarium specimens have often been germi- nated, but the writer knows of no other instance of the germination of dried uredospores, such spores being able also to infect a different host. These observations and experiments indicate that we have here a second step in the perfection of the uredo stage as a means of propagating the species. The first step, the attainment of sufficien hardiness to continue alive in the green plant over winter, has just been discussed. Even in this case the uredo, although quite active, at least displaces the resting spore, and in a measure performs its part. But as the perennial host becomes more like an annual and the plant dies nearly or quite to the ground, as in this particular case of the Sporobolus (which is quite different in this respect from the evergreen Poa pratensis, for example), necessarily, in the absence of teleuto- spores, the uredospore must be able to infect after a dormant period. The uredospore therefore becomes now practically a resting spore, but retains the appearance and manner of germination of the summer spore. Such a modification in form or function of any stage of a species to correspond with an unusual change of condition of climate or of the host may be considered as an emergency adaptation. It is easily understood how the change of conditions may be so severe as to necessitate still further modification of structure as well as function, simply as a means of protection. Such a development seems to have been actually reached in the species next discussed, which has resulted in the production of a distinct spore form, special- ized from the uredo, leaving still, however, a true uredo stage for summer propagation. PUCCINIA VEXANS FARL. There are probably no other species in all the Uredinez more inter- esting than this one, and certainly none that has been more perplex- ing. In this species there are three distinct spore forms aside from any ecidium or spermogonium that may possibly exist—true uredo and teleuto stages, and a peculiar one-celled form different from either of these. (Pl. II, figs. 2-9.) The species was at first made all the more puzzling by the rarity of the true uredo stage, which was not known to exist, or at least not reported, until 1890, when Dr. H. J. Webber, in the Catalogue of the Flora of Nebraska, reported its occurrence in that State. In certain seasons and localities the teleuto stage also is almost or entirely lacking. PUCCINIA VEXANS FARL. : 23 The species was first described by Peck as a Uromyces (U/. brandegez Pk.)@ on the basis of material collected by Mr. T. S. Brandege, in which specimens contained only the third spore form. Because of the discovery afterwards of two-celled spores associated with this third spore form, even sometimes in the same sorus, Doctor Farlow described it as a Puccinia (P. verans Farl.) in the Proceedings of the American Academy of Arts and Sciences, Vol. XVIII, pp. 82-83. At that time the true uredo stage had not been discovered. This third spore form is far more prevalent than either of the others as arule, but is sometimes entirely absent, leaving only the teleuto stage. It is distinct from either of the other forms in structure and appearance, and yet resembles both in some respects. It 1s larger than either of them, is strongly papillate, and has a much thicker cell wall, but on the other hand possesses the color and persistence of pedicels of teleutospores and appears to have pores like the uredospores. (PI. II, fig. 5.) Doctor Farlow, in his description, says: A species in which some of the sori contain only two-celled spores must certainly be held to be a Puccinia, and the perplexing question arises, are the one-celled spores a unilocular form of teleutospores similar to what is known in P. cesatii Schr., or are they the uredospores of this species? - I have not been able to find any other spores which represent the uredo of the species; and*never having seen the unicellular spores in germination, there is, so far as we yet know, no reason why they may not be the uredospores. On the other hand, their general appearance and the density of the cell wall would lead one to suppose that they were of a teleutosporic nature. Further conjecture is unnecessary, because, as the species is not at all rare in some localities, botanists who can examine the fungus on the spot ought to be able to ascertain whether the one-celled bodies produce promycelia or not, or else to discover the true uredo of the species. A full description of all three forms is given by Arthur and Holway in Descriptions of American Uredinee accompanying Fasicle IV of Uredinee Exsiccate et Icones.? After numerous unsuccessful trials during several years, the writer was finally able to germinate the third spore form, and, as suggested by Doctor Farlow, has in this way been able to determine its nature. In manner of germination it is exactly like the uredospore, the long simple germ tubes being produced through equatorial pores (PI. I, figs T and 8), but is like the teleutospore in germinating only after a dormant period and exposure to extremes of weather. The uredo and teleuto forms being already present and morphologically different from this form, it must be considered distinct. Because of the dual nature of this spore form, the writer has already proposed for it the name amphispore in a paper read before the Baltimore meeting of the Society for Plant Morphology and Physiology in 1900, only an abstract of which was published. The term has since been adopted by Arthur - @Bot. Gaz., 4: 127. Bul. Lab. Nat. Hist. State Univ. Iowa, Vol. V, pp. 329-830. ¢Science, Vol. XIII, p. 250. ~ 24 | INVESTIGATIONS OF RUSTS. and Holway,” and a second instance of the occurrence of this form is described by them for Puccinia tripsaci Diet. and Holw. The entire series of observations and experiments with this species made by the writer will now be described. The first cultures of amphispores were made January 15, 1894, at Manhattan, Kans. Both a water culture and one of a sterilized decoc- tion of manure were employed, with no result, the chief cause of fail- ure being probably that the experiment was too early in the season. Afterwards numerous other trials were made with no better success. In the meantime true uredospores were found on September 25, 1896, at Manhattan, Kans. Finally a successful culture of the amphispores was made on March 8, 1897, at Washington, D. C. The germination was excellent. An abundance of rather long germ tubes, not promycelia, was produced in forty-two hours, but only one to each spore. These germ tubes, unlike those of most uredospores, are quite colorless and clear. A few teleutospores were present, none of which germinated. The culture was an ordinary water drop, but was made in a new form of culture cell, constructed to special order and similar to the Van Tieghem cell, except that the glass ring is quite thin and drawn out into an open tube on each of two opposite sides, with the opening plugged with cotton wool, thus admitting sterilized air. This construction may or may not have increased the chances for-germination. The extreme weather conditions at the time, to which the specimens were first exposed, probably contributed most to the success of the culture. They were fastened to the roof of a near-by shed, and after several days of warm sunshine were thoroughly soaked with rain, which was followed by snow and then a severe freeze, soon after which the cul- ture was made. It is an interesting feature of the experiment that the specimens were received from Dr. David Griffiths, then at Aber- deen, S. Dak., and had been collected in September, 1896, and kept in the herbarium until sent to Washington. It was unfortunate that seedlings of the host were not available for making inoculations with these perfectly viable spores. Such an experiment is yet to be made. At Manhattan, Kans.,in 1897, the uredo was present in considerable abundance from June until late in October in grass plats on the Experiment Station farm. On July 8 inoculations were made with the uredospores of this species and with Acidium cephalanthi and LE. xanthoxyli on seedlings of Bouteloua racemosa without result. Further inocalations with uredospores on October 4 were successful, rust spots appearing in twelve days (PI. II, fig. 9), followed in nine more days with one sorus of amphispores. The uredosori are yel- lowish-brown and rather inconspicuous. On December 31 uredo- spores could not be found in the grass plats at Manhattan. «Bul. Lab. Nat. Hist., State Univ. Lowa, Vol: V, p.175. EXPERIMENTS WITH LEPTO-UREDINE. 25 At Lincoln, Nebr., a water-drop culture was made of Puccinia vexuns on March 15, 1898, resulting in a few germinations of the teleu- tospores in three days. Long promycelia were produced, but no sporidiola. None of the numerous amphispores present germinated. On September 29, 1899, all three spore forms were again found in the grass plats at Manhattan. Living host plants were transferred to Washington, D. C., and seedlings were started for further experi- ments, when other duties intervened and the work could not be continued. Certain facts concerning the relative abundance of the amphispores and teleutospores in different seasons and localities seem to harmonize quite well with the idea already expressed as to the function of the former. If it is the work of the amphispore to carry the species through unusually severe cold or drought, then this spore form should be relatively more abundant in dry periods and relatively more com- mon to the westward and northward in the Great Plains. These con- ditions are just what exist. The amphispore prevails almost entirely in the Dakotas and in western Kansas, western Nebraska, and eastern Colorado, and appears to have been more common in eastern Kansas during a dry period of several years than during a wet period. At the same time westward toward the mountains there is less chance for an Acidium to connect with the teleuto stage. EXPERIMENTS WITH LEPTO-UREDINEZ. It is generally supposed that teleutospores which are followed by an wecidium germinate only after a considerable period of rest, usually in early spring. As already mentioned under the discussion of sun- flower rust, the writer germinated teleutospores of this species readily in the autumn, and afterwards at different times during the winter. This readiness of germination, apparently at almost any date. is an indication in itself of an alliance to the lepto species. But, more than this, the autumn inoculations with material in which no uredospores could positively be detected nevertheless were, in some cases at least, followed first by spermogonia and then by the uredo! Of course occa- sional uredospores that may have been overlooked could have produced those few spots in which the presence of spermogonia was not certain. Here, then, is further evidence of the lepto tendency of the species. In addition, it is well known that the ecidium is rare and appears to have no fixed time of occurrence. Now, only the omission of the uredo is needed to make the rust a real lepto species. As it is, its position is more nearly that of a Hemi-puccinia than of an autcecious species. Experiments of this kind, united with critical field observa- tions, thus throw much light upon classification as to group position, as well as enabling us to connect stages. On the other hand, certain lepto species will be found to closely 26 INVESTIGATIONS OF RUSTS. approach other groups, and, indeed, after further experiment, may have to be placed in some other group. The following species have given interesting results in culture experiments. Rust oF CockLEsur (Puccinia xanthii ScHw.). Observations and culture experiments of the writer show that the rust of cocklebur is probably limited to one host and is distinct from the species on Ambrosia, and also justify the suspicion that it lies very near the border of the Lepto-uredinez, and may belong to another group. On March 1, 1897, the first water-drop culture made gave an excel- lent germination in forty-eight hours. Long promycelia were pro- duced, but no sporidiola. On February 13, 1897, at Washington, D. C., inoculations were made on seedlings of cocklebur and Ambrosia trijda, resulting in an infection of the former in eighteen days, but not of the latter. On March 12 a second experiment resulted in a Jarge number of infections of cocklebur seedlings in fourteen days. In all these cases spermogonia preceded the teleutospores in the infected spots. On October 8 of the same year an ecidium was found on cocklebur in considerable abundance, associated with the teleuto- sori, at Perkins, Okla. An inoculation on cocklebur seedlings, made at Lincoln, Nebr., on February 16, 1898, resulted in the production of spermogonia in ten days. The inoculating material had been col- lected in October, 1897. An ecidium on cocklebur was again found in abundance at Las Cruces, N. Mex., on July 11, 1899. Attempts should be made to infect the cocklebur with this ecidium. Doctor Farlow says an ecidium on Xanthium in Massachusetts is frequently followed by Puccinia xanthii.“ The ease with which artificial infections are made with this rust is at first surprising. So long as there is warmth and moisture, germina- tion occurs under almost any condition and at any time. Rust oF Vetver Lear (Puccinia heterospora B. axp C.). In the last-mentioned experiments the inoculating material was taken each time from dead leaves. The same was true in one experi- ment with the rust of velvet leaf, November 14, 1896, at Manhattan, Kans., in which seedlings of the host were infected in twelve days. For all these experiments the average time of incubation was about twelve days. In December, 1896, the infected plants of the last experiment were transferred from Manhattan to Washington, D. C., and material from these was used to inoculate new seedlings, which resulted in an infection in nine days. It appears, therefore, that the a@Proc. Amer. Acad. Arts and Sci., Vol. X VIII, p. 75. PERENNIAL SPECIES. ee incubation period is shorter if inoculating material is taken from liy- ing plants, and during the summer it is probably about the same as that of infections from uredospores. Numerous experiments were also made with other lepto species, including Puccinia grindelix, Pk., P. variolans, Hark., P. lygodesmiz, E. and E., and P. sherardiana, Korn, with results similar to those above mentioned. The writer has already called attention to the phenomenon of the formation of catenulate sporidiola in two of these species, 7. grindelix and P. variolans.“ PERENNIAL SPECIES. The chance for the continued existence of a rust through winter resistance of the uredo without the intervention of another stage has been discussed. Though such a condition can only exist on a peren- nial host, or at least one that lives over winter, it must not be sup- posed that the fungus itself is necessarily or even usually perennial. As fast as the leaves of the host die the spores simply drop on to the next lower and younger leaves and produce reinfection, the mycelium not extending through the base of the infected leaf into the next leaves. If, however, the mycelium is found within the rootstock and after a dormant period during midwinter follows the new shvots upward in early spring and again produces sori at the surface of the plant, the rust is a true perennial. This condition appears to exist in the following: species. ZNCIDIUM TUBERCULATUM E. AND K. It is now usually supposed that all secidial forms will likely be found to be connected with other stages, though there are probably more of these forms whose connections are at present undetermined than there are of Lepto-uredines. If any Acidium is more likely than another to be an independent species, certainly the probabilities are largely in favor of this species,which occurs on Callirrhoe involucrata,’ for there is no need of another stage to perpetuate it, though Roter host might give it a wider distribution. The striking orange-yellow color, large and otherwise conspicuous sori, and its complete attack of every portion of the host make this an unusually unique and attractive species (PI. I, frontispiece). A note con- cerning the hardiness of this species was published by the writer sev- eral years ago.© The words are here quoted: ‘* #cidium tuberculatum « Bot. Gaz., Vol. XVIII, pp. 455-456. b Though aa previously reported, this rust was found also on Callirrhoe alcxoides at Salina, Kans., in May, 1893. CBOtIGAZ-, Ol XC VALE... 453: 98 INVESTIGATIONS OF RUSTS. EK. and K.is still producing vecidiospores on Callirrhoe involucrata out- doors here at Manhattan at the time of this writing (October 15, 1893), and Mr. KE. Bartholomew, of Rooks County, Kans., tells me that he has seen in December eecidiospores on specimens of this host growing close by a large snowdrift. In the spring secidiospores of this species begin forming about the first day of April.” On December 20, 1893, after the above was transmitted for publication, the rust was found still alive although it had been under 4 inches of snow. In a water-drop cul- ture of some of the material four spores germinated in twenty-four hours. Since that time, at later dates in the winter the living rust has been found, but close within the rootstock, with a faint color still, but producing no spores. The peculiar manner of growth of the rust, permeating the entire host and producing scattering sori all along the stems to their bases, as well as on the leaves, and the difficulty of germinating the spores harmonize also with the idea of a propagation by perennial mycelium. Besides the above instance other cultures of the spores were made as follows: At Manhattan, Kans., May 20, 1893, spores from Callirrhoe alceoides, only a few germinations in forty- eight hours; at Manhattan, June 9, 1893, spores from C. involucrata germinated sparingly in twenty-five hours; at Manhattan, January 30, 1894, spores from C. tnvolucrata growing in greenhouse, fair germi- nation in sixty hours. In the winter of 1896-97 infected plants of C. involucrata were obtained from Kansas and grown in a greenhouse at Washington, D. C., and on March 17, 1897, inoculations of seedlings of the follow- ing grasses with spores from these plants failed to produce infections: Agropyron occidentale, A. richardsoni, Sitanion elymoides, Llymus canadensis, and Bouteloua racemosa. Rust oF PEUCEDANUM FC@NICULACEUM. An /Keidium occurs on this host in Kansas and Nebraska which has been reported as 2. anisotomes Reich., but the identity of which is not yet determined” satisfactorily to the writer. At certain places a Puccinia follows the Atcidium so closely that their connection is very probable. Both forms are particularly abundant at Manhattan, Kans. On April 25, 1893, at that place, it was determined by the study of many cross sections of the host plant that the mycelium of the A‘cid- ium extends into the rootstock. It is one of the earliest rusts in the spring to appear in that locality. These facts make it probable that this rust is also perennial. On the other hand, it is possible that the teleutospores of the Puccinia may produce a very early infection at the base of the young shoots, resulting in the Aicidium, although in some pocaliuiess no Puceinia has yet been found following ie ZKcidium. a aThe species is spat ile one ima jonesir Pk. aan ine eecidial stage present. RUST OF PEUCEDANUM FQNICULACEUM. toa) At Lincoln, Nebr., on March 24, 1898, teleutospores of this same Puc- cinia germinated in a water-drop culture in twenty-four hours. It should be noted that it is possible for a perennial rust to exist in an annual host, the mycelium of the rust being carried over winter in the seed of the host. Such an instance is practically certain in the Euphorbia rust already discussed. Granting that Doctor Eriksson’s experiments were accurate, there would be another example in Puc- cinta glumarum Eriks. and Henn. on wheat. Pee AT HS. DESCRIPTION OF PLATES. Puate I. Frontispiece. A perennial rust. —£cidium tuberculatum E. and K. on Cal- lirrhoe wnvolucrata Gr. PuatE Il. Fig. 1.—Seedling of Euphorbia dentata grown constantly under bell jar from rusted seed. Fig. 2.—Puccinia vexans Farl. on Bouteloua racemosa, both uredosori and amphisori being shown. (Natural size.) Fig. 3.—The same ure- dosori and amphisori shown in fig. 2 magnified 10 diameters. Fig. 4.—Uredo- spores of Puccinia vexans X 600. Fig. 5.—Amphispores of Puccinia vexans X 600. Fig. 6.—Teleutospore of Puccinia verans X 600. Fig. 7.—Germinating uredo- spore of Puccinia vexans X 300. Fig. 8.—Germinating amphispores of Puccinia verans X 300. Fig. 9.—Uredosori of Puccinia verans on young seedling leaf of Bouteloua racemosa produced by artificial infection with uredospores from the same host. (Natural size). o2 O PLATE. II. Bul. 63, Bureau of Plant Industry, U. S. Dept. of Agriculture. pee” Toast knee renee 2 ee = pares Ad C— RUSTS OF EUPHORBIA AND GRAMA GRASS. [Continued from page 2 of cover. ] . 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