Digitized by tine Internet Arciiive in 2011 witii funding from LYRASIS members and Sloan Foundation http://www.archive.org/details/reportofbotanist214clin s 43 Connecticut Agricultural ^"^-^^ Experiment Station NEW HAVEN, CONN. Report of the Botanist For Years 1917-18 G. P. CLINTON, Sc.D. (Being BuUetin 214, Connecticut Agricultural Experiment Station) CONTENTS Page Co-operative Potato Spraying in 1917 411 Fertilizer Experiments with Potatoes 421 Inspection of Phaenogamic Herbaria for Rusts on Ribes sps 423 Infection Experiments of Pinus strobus with Cronartium ribicola 428 The Bulletins of this Station are mailed free to citizens of Connecti- cut who apply for them, and to others as far as the editions permit. Issued Sept., 1919 CONNECTICUT AGRICULTURAL EXPERIMEOT STATION OFFICERS AND STAFF. BOARD OF CONTROL. His Excellency, Marcus H. Holcomb, ex-offi,cio, President. James H. Webb, Vice President Hamden George A. Hopson, Secretary Wallingford E. H. Jenkins, Director and Treasurer New Haven Joseph W. Alsop Avon Charles R. Treat Orange Elijah Rogers Southington William H. Hall South Willington Administration. E. H. Jenkins, Ph.D., Director and Treasurer. Miss V. E. Cole, Librarian and Stenographer. Miss L. M. Brautlecht, Bookkeeper and Stenographer. William Veitch, In charge of Buildings and Grounds. Chemistry. Analytical Laboratory. E. Monkoe Bailey, Ph.D., Chemist in charge. C. B. Mohison, B.S., C. E. Shepakd, (.,.,, ^, ,, ,_, ______ _„ r Assistajit (.hemtsts. M. d Esopo, PhB., H. D. Edmond, B.S., ' » Frank Sheldon, Laboratory Assistant. V. L. Chtirchill, Sampling Agent. Miss Alta H. Moss, Stenographer. Protein Research. T. B. Osborne, Ph.D., D.Sc, Chemist in charge. Miss E. L. Ferrt, M. S., Assistant. Botany. G. P. Clinton, Sc.D., Botanist. E. M. Stoddard, B.S., Assistant Botanist. Florence A. McCoRxncK, Ph.D., Scientific Assistant. G. E. Graham, General Assistant. Mrs. W. W. Kelset, Secretary. Entomology. W. E. Britton, PhD., Entomologist; State Entomologist. B. H. Walden, B.Agr., Phillip Garm.^n, Ph.D., M. P. Zappb, B.S., I. W. Davis, B.Sc, Assistants. Miss Gladys M. Finlet, Stenographer. Forestry. W.^^lter O. Fillet, Forester; also State Forester, and State Forest Fire Warden. A. E. Moss, M.F., Assistant State and Station Forester. Miss E. L. Avert, Stenographer. Plant Breeding. Donald F. Jones, S.D., Plant Breeder. C. D. HuBBELL, Assistant. Vegetable Growing. W. C. Pblton, B.S. CO-OPERATIVE POTATO SPRAYING IN 1917. G. P. Clinton, Botanist. L. F. Har"vet, Farm Bureau Agent. Nature of Experiments. This is the second report on co-operative potato spraying, the first having been made by G. P. Clinton and F. E. Rogers, former County Agent of New Haven County, in the Station's Report for 1916, pp. 355-64. The experiments for 1917 were confined to home-made 4-4-50 Bordeaux, this having proven most practical in the previous experiments, and were merely to determine how efficient spraying was under ordinary farm conditions, and, as it turned out, in a year when blight was not especially troublesome. It was planned to give four to six treatments according to weather conditions and with the equipment at hand. The conditions varied so at the different farms where the experiments were con- ducted that the details are given under each. Thanks are due the owners for their aid in conducting the experiments, which were made at the following places: Arthur D. Clark's, Charles R. Treat's, and S. D. Woodruff & Sons', Orange; S. A. Smith & Son's, CHntonville; Whittemore's Estate, W. M. Shepardson, Manager, Middlebury. Experiments were also planned at the farm of Robert Treat, Woodmont. Two sprayings were made by Mr. Treat, one about the 1st of July and the second on July 20th, but further treat- ments were omitted because of the dying condition of a large part of the field the last of that month. This unusual trouble may have been partly due to hce, but probably drought and unbal- anced fertilization, factors that figured so prominently in the wilt and prematuring of fields in this State in 1918, were as much to blame. No yields were taken from this field, as evidently the two sprayings had not been of value under these conditions. The first sprayings were made early in July at all the places before any signs of the blight had appeared. In fact the very first blight found that year in the State was on July 24th at South Manchester, and was not found in any of the sprayed fields until considerably later. Blight caused no very evident harm except in the Middlebury field, which was quite wet in spots. At the 412 CONNECTICUT EXPERIMENT STATION BULLETIN 214. Treat farm the vines were all dead from sun scorch before any signs of blight appeared. Their premature death during August was due to very hot weather on the last few days of July and the first of August. The damage caused by this hot weather made unnecessary the sprayings planned for the last of August, except at the Whittemore estate. The results of spraying were determined by yields taken of 100 foot lengths, in comparable rows of the different plots, and the yields per acj-e figured from these by the method indicated in the previous report. No figures for cost of labor or supphes were kept, but those given in the 1916 report apply fairly well. The details of treatments, observations and results at each place follow. At Arthur D. Clark's Farm. Mr. Clark's field of three or four acres was very conveniently situated to the barn with water supply, etc. The field of Green Mountains was in fine shape when the spraying was started and was on high ground, somewhat rolling, with variable soil condi- tions, especially as regards retention of moisture. A one-horse Iron Age power sprayer, with single nozzles provided with strainer attachments for each of four rows, was used. The four sprayings were made as follows: 1st, July 6th; 2nd, July 16th; 3rd, July 27th; 4th, Aug. 13th. The sprayed plots were gone over twice, in opposite directions, at each spraying. In the first two treat- ments arsenate of lead paste, rate of 4 lbs. per 50 gals., was used in the Bordeaux for potato bugs, and the checks were sprayed at the same time and rate with the paste in water. The plots were as follows: Rows 1 to 4. Check. Rows 5 to 36. Bordeaux (twice over). Rov>rs 37 to 40. Check. Rows 41 on. Sprayed as desired by Mr. Clark. The first twelve rows were planted with Maine grown seed, and the remainder with home-grown (one season) of same variety. On July 27th the vines of the Maine grown seed were distinctly larger and so more difficult to coat thoroughly with the spray than the home grown. Also on this date the effect of the poorer and more leachy soil in certain parts of the field began to show in the prematuring and yellowing of the vines, despite the fairly CO-OPERATIVE POTATO SPRAYING. 413 good fertilizer applied. At the time of the fourth spraying, August 13th, some of the vines were dying prematurely, especially on the poorer part of the field, and more of those from home grown than from the Maine grown seed. There was no blight present. The hot weather of the last of July with resultant drought conditions in the leachier soil was entirely responsible for the trouble. There was little difference between sprayed apd unsprayed plots. On Aug. 28th, one fourth of the vines were dead due to drought, with sprayed plots a little better than unsprayed. Found the first blight at this time on the low spot in the field but it appeared too late to cause much damage. Two rows of the Maine grown seed, from which Mr. Clark had cut six inches off the tops about two weeks before, were greener than the other vines in the rows on either side. The potatoes were dug October 15th. The results of the yields are given in Table 1. From this it can be seen: 1st, That the Maine grown seed yielded better than the home grown, as was indicated by the appearance of the vines earlier; 2nd, That in each case the sprayed plots yielded better than the corresponding unsprayed plots; 3rd, That the average increase was about 18 bushels per acre, enough to slightly more than pay the cost of the spraying at the current price of potatoes per bushel (probably $15.00 clear profit) ; 4th, That the greatest difference between the sprayed and unsprayed plots was shown on the wet end of the field where the blight had been found on the foliage doing some damage. At Charles R. Treat's Farm. Green Mountain potatoes were planted here on two or three acres of sod land, and had the usual good fertilization and cultiva- tion given by Mr. Treat. The sprayings were made with a one- horse 4-row Iron Age power sprayer with single nozzles provided with strainers. Part of the field was gone over once at each spray- ing with Bordeaux and part twice, the second time in the opposite direction. The sprayings were made on the following dates: 1st, July 2nd; 2nd, July 16th; 3rd, July 27th; 4th, Aug. 13th. In the first two treatments, arsenate of lead at the rate of 4 lbs. per 50 gals, was used in the Bordeaux, and in water for the checks. The plot's were as follows : Rows 1 to 5. Check. 414 CONNECTICUT EXPERIMENT STATION BULLETIN 214. TABLE 1. DATA FOR THE A. D. CLARK FARM, ORANGE. Treatment. Feet dug Row lbs. 1st. lbs. 2nd. lbs. Total. No. rot. Rate 1st. bu. per 2nd. acre Total Check. No Bordeaux (1) i 5 -1 100 2-3 70.0 17.5 87.5 0 169.4 42.4 211.8 Twice over Bordeaux 4 times. (1) . . . t s c 100 7-8 72.0 18.5 90.5 0 174.2 44.8 219.0 Twice over Bordeaux 4 times. (2) . 1 100 34-35 58.0 13.0 71.0 0 140.4 31.4 171.8 Check. No Bordeaux (2) 100 38-39 52.5 17.0 69.6 0 127.1 41.1 168.2 Check. No Bordeaux (1) . . . . T ( c 3 100 2-3 84.0 13.0 97.0 25 203.3 31.4 234.7 Twice over Bordeaux 4 times. (1) < 100 8-9 101.5 12.5 114.0 18 245.6 30.3 275.9 Totals, Check 300 2-3 38-39 2-3 206.5 47.6 254.0 25 166.6 38.3 204.9 Totals, Bordeaux 300 7-8 34-35 8-9 231.6 44.0 275.5 18 186.7 36.6 222.2 (1) Maine grown seed. (2) Home grown seed. Rows 6 to 20. Bordeaux, once over each treatment. Rows 21 to 81. Bordeaux, twice over each treatment. The field was low, quite level and fairly uniform in character. On July 27th the vines were in fine shape except a small spot in the twice over Bordeaux plot, where lice had caused some injury. On Aug. 13th, however, they showed one-half the foliage dead, so the treatment on this date did little good. By Aug. 28th they were four-fifths dead. No difference showed in favor of the sprayed plots, and no bhght was found at any tune in the field. There is no doubt that the vines were so severely injured by the three or four days of unusually hot weather the last of Jul}'' and Aug. 1st, resulting in premature death during August, that the spraying had not yet begun to produce the beneficial effects that usually appear from the last of August on. The vines here suf- fered more from this hot spell than at any of the other farms. One row next the corn, which shaded it somewhat, kept green longer than the others. CO-OPERATIVE POTATO SPRAYING. 415 TABLE 2. DATA FROM THE C. R. TREAT FARM, ORANGE. Treatment. Feet dug Row lbs. 1st. lbs. 2nd. lbs. Total. No. rot. Rate 1st. bu. per 2nd. acre Total Check. No Bordeaux 100 2-3 65.5 16.0 81.5 0 158.5 38.7 197.2 (1) Once over Bordeaux 4 times (1) 100 7-8 56.5 15.5 72.0 0 136.7 37.5 174.2 Twice over Bordeaux 4 times.. .... (1) 100 21-22 53.5 13.5 67.0 0 129.4 32.7 162.1 Check. No Bordeaux 100 3-4 73.0 13.5 86.5 0 176.6 32.7 209.3 (2) Once over Bordeaux 4 times (2) 100 8-9 67.5 16.5 84.0 0 163.4 39.9 203.3 Twice over Bordeaux 4 times.. . . . . (2) 100 21-22 67.5 10.5 78.0 0 163.4 25.4 188.8 Totals, Check. 200 2-3 3-4 138.5 29.5 168.0 0 167.6 35.7 203.3 Totals, Bordeaux once over 200 7-8 8-9 124.0 32.0 156.0 0 150.0 38.7 188.7 Totals, Bordeaux twice over 200 21-22 21-22 121.0 24.0 145.0 0 146.4 29.0 175.4 (1) West side, south end of rows. (2) West side, center of rows. The potatoes were dug on Sept. 27th. The results of the yields are given in Table 2. From the results and the observations made, it is evident: 1st, That the spraying did no good; 2nd, This was due to the premature death of the vines resulting from the sudden hot spell in July and August, before any bhght got started; 3rd, The trampling of the ground and vines in spraying resulted in a decreased yield, shown most markedly in the twice over Bordeaux plots. Ordinarily where the vines are not Idlled prematurely, this sHght injury due to trampling is overcome later in the season and additional gain made through the greater vigor and lon- gevity of the sprayed vines. At S. D. Woodruff & Sons' Farm. As at the other places the potatoes were Green Mountains, with the fertilization and cultivation as ordinarily given by the owner. The field was similar to that at the Clark farm, being somewhat 416 CONNECTICUT EXPERIMENT STATION BULLETIN 214. lower and perhaps less variable in soil conditions, though none the less rolling. The planting, made with a planter, showed quite a few misses giving an uneven stand in the rows in scattered places. The one-horse Iron Age power sprayer used here, while of the four-rowed type with a single nozzle to a row, had a some- what stronger pump, that gave a more even distribution of spray material. The sprayings were made on the following dates: 1st, July 6th; 2nd, July 16th; 3rd, July 27th. The fourth spraying planned for Aug. 13th was omitted because the machine was not available. Poison for bugs was used in same way as at the other farms. The plots were as follows : Rows 1 to 16. Check. Rows 17 to 56. Bordeaux, twice over each time in opposite directions. Rows 57 to 60. Check. Row 61 on. Sprayed as desired by owner. On August 13th the field was somewhat weedy, and by Aug. 28th, the weeds were so large and abundant as to cause more or less damage. On neither of those dates did the vines show as much injury from the hot weather of July as did those at either the Clark or the Treat farm. This was probabl}'" due to better soil conditions for retaining moisture. Blight had not appeared in the field up to the last of August. Little difference was seen between the sprayed and unsprayed parts of the field. The potatoes were dug on Sept. 25th. The results are shown in Table 3. The conclusions are as follows: 1st, That the spraj^ed plots gave a very slight increase over the unsprayed; 2nd, That there was more variability in yield between the two checks than there was between them and the Bordeaux plots, probablj^ due to uneveness of stand and soil conditions, though we tried to avoid such in selecting the spots that were dug; 3rd, The few sprayings given, the weediness of the field, the absence of bhght, etc., made conditions such that very favorable results from the spraying could not be expected. At S. A. Smith & Son's Farm. The Green Mountain potatoes at this place were sprayed the first time with a hand-power barrel pump placed on a wagon to which was attached a stationary nozzle arrangement for spray- CO-OPERATIVE POTATO SPRAYING. 417 TABLE 3. DATA FROM THE S. E . WOODRUFF & sons' FARM, ORANGE. Treatment. Feet dug Row lbs. 1st. lbs.- 2nd. lbs. Total. No. rot. Rate 1st. bu. per 2nd. acre Total Check. No Bordeaux (1) 100 14 81.5 15.5 97.0 8 197.2 37.5 234.7 Twice over Bordeaux 3 times (1) 100 19 72.0 15.5 87.5 0 174.2 37.5 211.7 Check. No Bordeaux 100 58-59 64.0 9.5 73.5 6 154.9 23.0 177.9 (2) Twice over Bordeaux 3 times (2) 100 51,55 75.0 13.0 88.0 5 181.5 31.5 213.0 Totals, Check 200 14 58-59 145.5 25.0 170.5 14 176.1 30.3 206.4 Totals, Bordeaux 200 19 51,55 147.0 28.5 175.6 5 177.9 34.5 212.4 (1) Rows next road. (2) Rows center of field. ing four rows, each from a single nozzle. This worked so poorly that part of the rows were gone over three times to thoroughly coat them. The next two sprayings were made by hand with two lines of hose and were done more thoroughly than at any other place. The first two sprayings contained powdered lead arsenate at rate of 2 lbs. per 50 gals. Bordeaux, for the bugs, and the checks received similar amounts in water. The sprayings were made on following dates: 1st, July 6th; 2nd, July 17th; 3rd, Aug. 6th. The abundance of weeds made it undesirable to give the fourth spraying. The plots were as follows: Rows 1 to 4. Check. Rows 5 to 48. Bordeaux, thorough hand treatments. Rows 49 to 55. Check. On August 6th the field was becoming very weedy, and on Aug. 30th the weeds were so large and numerous as to seriously inter- fere with the crop, except in six rows where they had been pulled on Aug. 6th. The vines suffered little from the July hot spell and on Aug. 30th were greener than at any of the Orange farms. The first check rows showed little blight on Aug. 30th; how- ever, the second check rows, in a lower damper part of the field, showed more. The spray at this time had mostly washed off the vines. 418 CONNECTICUT EXPERIMENT STATION BULLETIN 214. TABLE 4. DATA FROM S. A, SMITH & son's farm, CLINTON VILLE. Treatment Feet dug Row lbs. 1st. lbs. 2nd. lbs. Total No. rot Rate 1st. bu. per 2nd. acre Total Check. No Bordeaux 100 2-3 64.5 13.5 78.0 5 156.1 32.7 188.8 (1) Twice over Bordeaux 3 times (1) 100 5-6 81.0 15.5 96.5 3 196.0 37.5 233.0 Twice over Bordeaux 3 times (2) 100 43-44 48.5 15.5 64.0 0 117.4 37.5 154.9 Check. No Bordeaux (2) 100 50-51 53.0 22.0 75.0 2 128.3 53.2 181.5 Totals, Check 200 2-3 50-51 117.5 35.5 153.0 7 142.2 42.9 185.1 Totals, Bordeaux 200 5-6 43-44 129.5 31.0 160.5 3 156.7 37.5 194.2 (1) Weeded. (2) Not weeded. The potatoes were dug October 8tli. The results are given in Table 4. From this experiment it is seen: 1st, That the sprayed vines gave a little better yield than the unsprayed, about enough to pay for the cost of the treatments; 2nd, That the part of the field kept thoroughly weeded showed greater difference in favor of the spraying and also in favor of weedmg. We do not know why Bordeaux plot 2 gave a smaller yield than check plot 2, unless the former was from home grown and the latter from Maine grown seed which was used in this end of the field. At Whittemore's Estate Farm, Middlehury. This field of several acres of Green Mountains was on a hill side and part of one end was quite moist even in dry weather, so that in the early season the potatoes were nearly smothered out there. It had been in sod the previous year, top dressed in the spring, and when plowed under had been so very liberally fertilized that the soil was in unusually good condition. The vines were sprayed with the large two-horse, 4-row Iron Age power sprayer that had three nozzles to a row, one above and on either side. The power was sufficient to give a very misty spray that with slow driving coated the vines in fair shape with the one spraying that was given at each treatment. Arsenate of lead was used in the first two treatments and on the check for bugs. The spraj^ings were CO-OPERATIVE POTATO SPRAYING. 419 made on the following dates: 1st, July 3rd; 2nd, July 11th; 3rd, July 19th; 4th, July 30th; 5th, Aug. 14th; 6th, Aug. 27th; 7th, Sept. 3rd. The plots were as follows : Rows 1 to 12. Bordeaux, once over. Rows 13 to 16. Check. Rows 17 on. Bordeaux, once over. The hot weather did not hurt this field and it remained green much longer than any of the others. In fact at the time of digging, Oct. 16th, some of the vines were still green! One of the largest hills, the vine of which was unusually luxuriant, yielded seven large potatoes and two small ones, a total weight of five and a half pounds. The tubers on the whole were rather large, one of the largest weighing eighteen and a half ounces. The large yield and large size of tubers were due to the good fertilization and the extended growth period of vines resulting from the spraying. Blight eventually appeared in September and caused death of the foHage and rot of the tubers especially in the wet area, and to a less extent in the unsprayed drier part of the field. The yields are shown in Table 5. An examination of this shows: 1st, That the spraying very considerably increased the yield in TABLE 5. DATA FROM THE WHITTEMORE ESTATE FARM, W. SON, MANAGER. M. SHEPARD- Treatment. Feet dug Row lbs. 1st. lbs. 2nd. lbs. Total. No. rot. Rate 1st. bu. per 2nd. acre Total Once over Bordeaux 7 times. .. . 100 10-11 124.6 11.5 136.0 3 301.3 27.8 329.1 Check. No Bordeaux 100 14-15 95.5 7.5 103.0 60 231.1 18.2 249.3 Once over Bordeaux 7 times 100 18-19 143.5 8.0 151.5 11 347.2 19.4 366.6 Once over Bordeaux 7 times.. . . (1) 100 10-11 85.5 8.0 93.5 106 206.9 19.4 226.3 Check. No Bordeaux 100 14-15 22.5 6.0 28.5 257 54.5 14.5 69.0 (1) Once over Bordeaux 7 times.. . . (1) 100 18-19 34.0 6.0 40.0 253 82.3 14.5 96.8 Totals, Check 200 14-15 14-15 118.0 13.5 131.5 317 142.8 16.3 159.1 Totals, Bordeaux 400 (2) 10-11 (2) 18-19 387.5 33.5 421.0 373 234.4 20.3 254.7 (1) Unusually wet spot covering only small part of the field. 420 CONNECTICUT EXPERIMENT STATION BULLETIN 214. each case over the adjacent unsprayed rows; 2nd, This increase averaged 95 bushels per acre; 3rd, The increased yield was in part due to the prolonged life of the vines, and in part to pre- venting rot of the tubers; 4th, The spraying did not prevent rot in the very wet part of the field, where considerably over half of the tubers rotted though it helped somewhat even there. General Conclusions. These were potato spraying experiments, chiefly with horse- power sprayers, carried on under the ordinary operations at five different farms. The hot weather, of three days the last of July and the 1st of August, seriousl3^ interfered with the results by prematurely killing or injuring the vines in August in two of the fields, and to a small extent in two more. This rendered unneces- sary the last one or two sprayings that had been planned. Blight caused no conspicuous injury except in one field. The spraying harmed rather than helped in one field, due to tramphng of vines in spraying and the premature death of the vines from drought before the effect of spraying showed; two fields were benefitted about enough to pay for the cost of spraying; one field gave an increase about (18 bushels) slightly above the cost; one field, where blight was prevented, gave an increase (95 bushels) very greatly in excess of the cost of spraying. FERTILIZER EXPERIMENTS WITH POTATOES. E. H. Jenkins, Director. G. P. Clinton, Botanist. The following is an account of observations on the yields of potatoes as affected by different fertilizers, especially as regards potash, conducted by Mr. W. M. Shepardson, Middlebury, Conn., the writers making the weighings at digging time, and by Mr. F. C. Davis, of Somers. The first lot, northwest of Mr. Bristol's house, was in turf the previous spring and had not been cultivated for many years. In 1917 it was plowed, dressed with 25 loads of manure to the acre, and the fertilizers named were put in the drill at the rate of 1000 pounds per acre. The rows were 2^^ feet apart. The Green Mountain potatoes were planted by machine on June 9th. The stand obtained was quite uniform. The potatoes were dug on Oct. 19th, and the crop on the two central rows of each plot, 100 feet long, was weighed and sorted into firsts and seconds. Thefee tubers were obviously scabby where ashes were used, and more scabby where 2000 pounds of ashes were used than where half that amount was apphed. The weights in lbs. of the potatoes on the 2 rows were as follows : lbs. lbs. lbs. *Est. Total Fertilizers. Firsts. Seconds. Total. Bu. per acre Essex 4-8-4 (1916 stock) 112% 40 1523^ 184 . 5 " 4-10-0 122% 37% 160 193.6 " 4-10-0, 1000 lbs. ashes per acre 132% 37% 170 205.7 « 4-10-0,2000 " " " " 157% 22% 180 217.8 Buffalo 2-9-4 (Templeton) 117% 30 147% 178.5 Essex 4-8-4 (1916) 127% 35 162% 196.6 Bowker 3%-9-4 (1916) 122% 42% 165 199.7 Buffalo 2-9-4 (Templeton) 117% 35 152% 184.5 Buffalo 2-9-4 (Outside rows) 125 27% 152% 184.5 *Estimated on basis of an acre field 16 by 10 rods, rows running length- wise of field, and 3 feet apart. The most noticeable things are that the duplicates with Essex and Buffalo in different parts of field gave rather uniform results indicating uniformity in the soil of the field. The addition of ashes to the Essex 4-10-0 increased the yield and 2000 lbs. increased it more than 1000 lbs., particularly in the No. 422 CONNECTICUT EXPERIMENT STATION BULLETIN 214. 1 potatoes. The ashes however induced scab, though not enough to seriously damage market quahty. On a neighboring field planted to Green Mountain on June 8th in rows 2 ft. 10 in. apart, 2 rows each 150 feet long were dug in each plot. 1000 lbs. of the fertilizers were used and on some plots varying amounts of wood ashes were added. *Est. of Firsts. Seconds. Totals. Total bu. per lbs. lbs. lbs. acre. Essex 4-8-4 180 75 255 205.7 " 4-10-0, no ashes, 200 55 255 205.7 " " " « 1000 lbs. ash 165 70 235 189.6 « " " « 2000" " 230 80 310 250.1 " " " « 3000" " 250 60 310 250.1 *Estimated. on basis of an acre field 16 by 10 rods, rows running length- wise of field, and 3 feet apart. Here 1000 lbs. ashes had no apparent effect, 2000 and 3000 lbs. ashes increased yield to same amount. Scab was more abundant where ashes were used than on plots where not used, but there was not much difference due to the different amounts used. In neither field did the Essex 4-8-4, with potash, give a better yield than the 4-10-0 without it. However, in both fields the ad- dition of a ton or more of wood ashes to the Essex 4-10-0 materially increased the jdeld, due either to the greater amount of potash or to the lime they contained. Mr. F. C. Davis, of Somers, reports in 1918 more favorable returns from potash, where he used it alternating on seven strips of twelve rows each, in a 3-8-3 formula in comparison with a 4-10-0. The land was a gravelly loam in corn the previous year. The fertilizers were apphed in three doses as follows: 800 lbs. before the first harrowing, working it in thoroughly with the stalks and plowing under, 400 in the planter and 600 at the time of the second cultivation. There was no difference between the strips during the growing season until the last ten days, the potash strips remaining ahve that much longer. The difference in yield was about 50 bushels per acre in favor of the potash fertilizer. This at the price the potatoes were sold was a gain of $75 per acre or, deducting the extra cost of this fertilizer, a net gain of INSPECTION OF PHAENOGAMIC HERBARIA FOR RUSTS ON RIBES SPS. G. P. Clinton, Botanist. Not infrequently one can find specimens of certain fungi easier by looking through a collection of flowering plants in an herbarium than by going out doors and looking for them on the hving hosts. This is true of certain smuts and rusts and especiWlly so if the de- sired hosts do not occur in one's vicinity but are found in a large phaenogamic herbarium near by. Thinking that such a search through a number of herbaria perhaps might throw light on the early occurrence of Cronartium ribicola in this country, the writer in 1916 and 1917 carefully looked over the specimens of Rihes, including Grossularia, in the following eastern herbaria: (1) Conn. Agr. Sta. Herb., (2) Conn. Bot. Club Herb., (3) Yale Univ. Herb., (4) N. Y. Bot Card. Herb., (5) Columbia Univ. Herb., (6) Grey Herb., (7) N. E. Bot. Club. Herb., (8) U. S. Nat. Herb. Re- quests were also sent to several central and western herbaria that leaves containing suspicious rust specimens be sent the writer and several such were received from the following: (9) Mo. Bot. Gard. Herb., sent by Greenman, (10) Univ. of Wash. Herb., by Hotson, (11) Univ of Calif. Herb., by Jepson. No rusts, however, v/ere foimd on specimens sent from the last two herbaria. While this investigation did not throw any light on the occurence of Cronartium ribicola in this country, except what might be considered negative evidence, still information was obtained of its existence elsewhere and of the distribution, hosts, etc., of three other rusts in this country. We have thought it worth while to record here this data, together with some general remarks on the same. The figures in parentheses, following the name of the col- lector with each collection, refer to the herbarium, as numbered in the preceding paragraph, in which the Rihes were examined. Most of these fragmentary specimens containing the enumerated rusts are now in the herbarium of the Conn. Agr, Exp. Station. Besides these rusts several other fungi were observed but no particular attention was paid to them. They included the fol- lowing: Gleosporium Rihis (Lib.) Mont. & Desm., on Rihes Lobbii, KHckitat Co., Wash., 7 Au. 1897, Suksdorf (6); on Rihes nigrum, Mt. Lancaster, Coos Co., N. H., 25 Au. 1913, Pease (7). Septoria 424 CONNECTICUT EXPERIMENT STATION BULLETIN 214. aurea destruens E & E., on Rihes aureum, Mobridge, S. Dak., 28 Jl. 1907, Bailey (8). Aecidium Grossulariae (P.) Schum. This fungus has now been proven by infection experiments to be the I stage of Puccinia Grossulariae (Schum.) Lag. with its II and III stages on Car ex sps. Whether or not all of the aecia on the various species of Rihes scattered over the country are the same thing can only be determined by further inoculation tests. Arthur (Journ. Myc. 8:53. 1902.) has described another Puc- cinia, P. albiperidia, with its II and III stages on Carex and its I stage on Ribes sps., distinguished by its white or nearly white aecia {Aecidium alhiperidium) . The same author (Mycologia 4: 14. 1912.) thinks that Uromyces uniporulus Kern also has its aecia on Rihes. We have however grouped all the specimens reported here under Aecidium Grossulariae as they showed no evident difference. This rust occurs very commonly on herbarium material and in the immature stage resembles somewhat the II stage of Cronartium rihicola. However, one soon learns to distin- guish it in this stage with the hand lens through the larger size of the aecia and the presence of pycnia. This rust was collected on eleven different hosts as follows : On Rihes americanum (R. floridum) : — ^New Haven, Ct., 27 My. 1879, Livingston (3); Oxford, Ct., 23 Je. 1901, Harger (2); Bellevue, Wise, 27 My. 1882, Schnelle (6); Norway, Neb., 22 Je. 1893, Rydberg (6, 8). On Rihes hracteosum: — Chilliwach Valley, B. C, 8 Jl. 1901, Macoun (8). On Rihes (Grossularia) Cynoshati: — Jackson, N. H., 29 Jl. 1876, Allen (1); Orono, Me., 25 Au. 1913, Pease (7); Northumberland, N. H., 31 Jl. 1909, Pease (7); Manchester, Vt., 30 Je. 1898, Day (7); Colebrook, N. H., 13 Jl. 1907, Pease (7); Kingston, Ont., 5 Je. 1902, Fowler (8); New Harpersfield, N. Y., 8 Je. 1906, Toppin (8). On Rihes (Grossularia) divaricatum: — Yellowstone, Neb., Au. 1854, Hayden (9); Chehalis Co., Wash., 10 My. 1897, (4). On Rihes (Grossularia) gracile: — Near Minneapolis, Minn., My. 1891, Alton (3). On Rihes (Grossularia) hirtellum: — Berhn, Mass., 13 Je. 1915, Winslow (7); Clinton Co., la., 23 Ap. 1878, Butler (1); Foxcroft, RUSTS ON RIBES IN HERBARIA. 425 Me., 25 Je.,1894, Fernald (7); Dead River, Me., 19 Au. 1896, Fernald & Strong (7). On Rihes lacustre: — Sherburne, Vt., 18 Je. 1899, (4); Pittsburg, N. H., 5 Jl. 1907, Pease (7). On Rihes prostratum:—Mt. Washington, N. H., 24 Je. 1893, Greenman (9), 24 Je. 1898, Williams (7); Straits Belle Isle, Lab., 1 Au. 1910, Fernald & Wiegand (6);Orono, Me., 1 Jl. 1892, Fernald (7); Cumberland, Me., 29 My. 1902, Chamberlain (7); Mt. Mansfield, Vt. 2 Jl. 1897, Wilhams (7); Oakham, Mass., 12 My. 1912, Fernald (7); Adams, Mass., 4 Je. 1898, Churchill (7). On Rihes (Grossularia) rotundifolium: — Ames, la., Hitchcock (9); la., 1871, (9); CKnton Co., la., 22 Ap. 1878, Butler (1). On Rihes {Grossularia) saximontanum: — Platte Canyon, Natrona Co., Wy., 7 Je. 1901, Godding (9). On Rihes {Grossularia) setosum: — ^Buffalo, Wy.,Jl. 1900, Tweedy (3) ; Bozeman, Mont., 18 My. 1901, Jones (8). Coleosporium rihicola (C. & E.) Arth. This is a western rust of which the aecial stage apparently is not yet known. It is probably some Peridermium on the leaves of Pinus sps. The uredinial stage was first described in 1878 (Grev. 6: 86.) by Cooke & Ellis from the Rocky Mts., on Rihes sp. Arthur (N. A. Flora 7: 86. 1907) who placed it under the genus Coleosporium and described the telial stage, gives Rocky Mountains {Colorado) and Rihes {leptanthuin) as the type locality and host. In 1885 Peck (Bull. Torr. Bot. Club 12 : 36.) again described this species on Rihes from New Mexico under the name Uredo Jonesii. It is interesting to note here that at least 24 years before Cooke & Ellis first described the fungus it was unknowingly collected by Bigelow (Botanist, Whipple Exp. R. R. Route Miss. R. to Pacific Ocean, Fort Smith to the Rio Grande in 1853-i) on Ribes leptan- thum as shown by specimens taken from this host in the Gray Herbarium. Arthur in his monograph cites as hosts five species of Rihes from eight states. We list here at least eight hosts from ten different localities, as follows: On Rihes aureum: — Nogal Canyon, White Mts., New Mex., 17 Au. 1901, Wooton (II, 4), (III, 8). On Rihes {Grossularia) hirtellum: — Black Tail Deer Creek, Yellowstone Park, III, Au. 1884, Tweedy (3). 426 CONNECTICUT EXPERIMENT STATION BULLETIN 214. On Ribes lacustre (R. echinatum) : — Cascade Mts., Wash., II, 10 Au. 1893, Allen (4). On Ribes {Grossularia) leptanthum: — Fort Smith to the Rio Grande, Whipple Exp., Ill, 1 853-4, Bigelow (6). On Ribes montigenum: — Sandia Mts., Sandoval Co., New Mex., Ill, 3 Au. 1910, Wooton (8); Sandia Mts., Balsam Park, New Mex., II, 17 Ap. 1914, Miss Ellis (4). On Ribes {Grossularia) pinetorum: — Chloride, New Mex., Ill, 12 O. 1909, Goldman (8). On Ribes triste (R. rubrum) : — Yakon Valley, 40 Mile River, II, 17 Je. 1902, CoHier (8). On Ribes TFoZ/w:— Sandia Mts., Balsam Park, New Mex., Ill, 28 My. 1914, Miss Ellis (4). On Ribes {Grossularia) sp.: — Calif., Ill, 11 S. 1909, Rusby (4). Cronartiuni ribicola F. deW. The search through various herbaria for this fungus was to learn, if possible, whether it occurred in the New England states earher than the first reported collections made in 1914, and whether it was native in Colorado on Ribes longiflorum as indicated by the collections of Bethel. Nothing was learned along either of these lines. The western Cronartiwn in its II stage was first col- lected on Ribes longiflorum by Bartholomew in Stockton, Kans., Aug. 22, 1892, but has never appeared there since. During the last ten years Bethel has collected it a number of times on the same host, in both stages, at Boulder, Denver, and also other places in Colorado where it appears to be native. Recent experiments by government investigators have shown these collections to be distinct from our eastern introduced species altho Ribes longiflorum is considered by some as a synonym of Ribes odoratum, a common host in New England for Cronartiwn ribicola. In our search of herbaria, however, we did not find any Cronartium on Ribes longiflorum, though we did secure Cronartium ribicola on three speci- mens, two from Europe and one from Asia, as follows : On Ribes aureum {R. leiobotrys) : — Cult, plants in Berlin, Ger- many, II, III, 5 My. 1893, Koehne (6). On Ribes {Grossularia) divaricatum {R. irrigum) : — Cult, plants in Berlin, Germany, 9 Au. 1895, Koehne (6). On Ribes sp:— C. China, W. Hupeh, My. 1900, Wilson, no. 515, (4). EUSTS ON RIBES IN HERBARIA. 427 Puccinia Rihis D. C. This fungus is found in Europe and America, but is apparently not very common here, at least the writer has never • collected it in the field. It seems to have a northern distribution and has been reported from New York by Peck, Wisconsin by Davis, Minnesota by HoUway, and probably from other states, and was found on several hosts, but not on the variety reported here. Peck describes it as a new species, Puccinia pulchella in 1873. There is only the tehal stage in this rust. On Rihes triste var. alhinervium: — VanBuren, Me., 24 Jl. 1893, Fernald (7). INFECTION EXPERIMENTS OF PINUS STROBUS WITH CRONARTIUM RIBICOLA.* G. P. Clinton, Botanist. Florence A. McCormick, Scientific Assistant. HISTORICAL CONSIDERATION. Introduction of Blister Rust in Connecticut, etc. In an article dealing with heteroeceous rusts found in Connecticut, published by the Station Botanist (1 p. 394) in his Report for 1907, the state- ment was made that the blister rust was ''liable to be introduced on white pine imported from Europe". In April, 1909, Mr. F. A. Metzger, a forester employed by Mr. C. F. Street at Wilton to set out a plantation of 10,000 three year old white pine seedhngs imported through the State Forester from Germany, found fifty to *In order that the reader may gain at the start a fair idea of the fungus discussed here, a brief outline of its life-history follows: White Pine Blister Rust is the common name for the first or I stage of a rust im- ported accidentally into America on seedling white pines from Europe. The rust enters the pines through the pores, or stomata, of the needles in the fall. Usually within a year or two after infection, during late summer and fall, lemon-yellow drops containing minute spore-like bodies called pycniospores, ooze out from yellowish (but eventually brownish) areas on the bark, forming the O or pycnial stage of the fun- gus. The use of these so-called spores has never been determined. The next spring (the last of April to the middle of June) after the ap- pearance of the pycnia, the first true spore stage, called the I or aecial stage, appears. This forms small, white, fragile, irregular eruptions on the bark projecting for about a quarter of an inch. They soon break open at the top disclosing an orange-yellow dusty mass of spores, the aecial spores. The aecial spores are blown by the wind, or possibly carried by in- sects to the leaves of the alternate hosts, which compiise the various currants and gooseberries belonging to the genus Ribes. Germinating under favorable conditions of moisture, these spores send their germ tubes through the stomata, chiefly situated on the under side of the leaves, and usually within 7 to 12 days give rise there to the II stage of the fungus, called the uredinial stage. This shows as small roundish pustules, smaller than the head of a pin, that contain thi yellow semi- dusty urediniospores. These are washed over the leaf or carried to the leaves of same or other plants and, on germinating and gaining entrance to the tissues, produce similar pustules. Through the summer several generations of these urediniospores may be produced spreading the dis- * INFECTION OF PINE WITH BLISTER RUST. 429 one hundred infected with an unknown disease. He brought these to the Station and the trouble was later identified by the botanist (2 p. 731), who was then absent in Japan, as the white pine bhster rust. This was the first definite finding of the bhster rust in this state and one of the first in America, as about the same time it was also found on imported seedlings set out in several other New England states and New York. It is quite probable that the disease was brought into Connecticut at an even earlier date, as several plantations from foreign stock had been started in 1907, while nurserymen and others, on whose premises the disease has since been found in two cases, had imported seedHngs and trees much earlier. There is also considerable evidence to show that it was brought into some of the other states some years before it was definitely first found in 1909. In New York it was introduced at least before 1906. ease more or less widely by this repetition. The black currant is especially susceptible to attack. From midsummer on, the III or telial stage develops on the Ribes leaves often appearing in the same pustules following the II stage. ■ This last stage shows as minute reddish-brown hairs about 1 or 2 mm. long and more or less thickly covering the under surface of the leaves. These hairs aie composed of leliospoies adhering permanently together. They germinate immediately under favorable moisture conditions and give rise to germ threads bearing very small secondary spores, spotidia, that are blown by the wind to the pine needles, and there gain entrance as already indicated. Infected seedlings before the I stage appears in the spring are usually detected by their bunched leaves and soft swollen stems. When the fruiting pustules appear they are quite conspicuous and the disease is easily recognized. After these disappear in late June, there remains only the roughened dead bark or a yellowish-green area of invaded smooth bark which will break out the next year, to indicate infection. Once the cambium is killed all around the stem the parts above die. Very young infected seedlings do well to live a year, but those two or three years old may live for several years. On older trees if the infec- tion is at the ends of the twigs the damage is not serious, but once the main trunk becomes invaded the tree is doomed though it may re- main in vigorous growth for several years and seem perfectly healthy on casual examination of the foliage. Elimination of Ribes in the vicinity of seed beds, thorough spraying of the beds with Bordeaux after midsummer if grown in an infected region, use of uninfected seedlings only for planting, inspection of plantations from foreign stock for infected pines, destruction of all wild or cultivated Ribes in plantations and for 300 yards around the same, are precaution- ary measures advocated for this state. 430 CONNECTICUT EXPERIMENT STATION BULLETIN 214. Upon positive identification, the botanical and forestry depart- ments, in co-operation with the U. S. Department of Agriculture, inspected during 1909 most of the larger plantations scattered over the state, with the result that the blister rust was found in small amounts in several of them. All of the infected trees foimd were destroyed. In 1910 most of these plantations were re-inspected and several smaller ones were inspected for the first time. About 645,000 out of the 740,000 imported trees that had been set out, were thus inspected once or twice during the two years. As no trees were found infected in 1910, the inspection was practically discontinued. An account of this work appears in the botanist's report for 1909-10. In the spring of 1912, Mr. Walden, inspecting an importation of white pine from Holland at one of the local nurseries, found some of the seedHngs badly infected, and upon identification as this rust by the botanist (3 p. 347) Dr. Britton ordered them all destroyed. Since that year importation of white pines from coun- tries where the disease occurs has been prohibited by a quarantine of the U. S. Department of Agriculture. The first outbreak found in this State on Rihes species, the alternative host for the II and III stages of this fungus, was found by the senior writer (3 p. 348) on a few black currants at the home of Mr. H. B. Birdsey at East Meriden, Conn., in October of 1912. The origin of this infection has never been determined, since infected pines have not been found in this general region, though the rust has usually appeared each year since on these bushes. Nature of Recent Work. In 1916 the rust having become promi- nent in certain plantations in northeastern United States and Cana- da, and especially wide-spread on the Rihes, the U. S. Depart- ment of Agriculture, and the several interested states, undertook anew methods looking for its control within the infected areas, and quarantine laws have since been passed regulating the ship- ment of five-needle pines and black currants from these to other parts of the country in order to prevent its introduction into other states. This necessitated further work in Connecticut. The forestry department of this station in co-operation with the United States Department of Agriculture, undertook especially the practi- cal work deahng with inspection and control. The botanical department, while also helping with this phase, took as its special INFECTION OF PINE WITH BLISTER RUST. 431 problem the scientific study of the rust in its various aspects. The work under the direction of the forester has been carried on by funds from the U. S. Department of Agriculture and state appropriations, while that by the botanical department from state appropriations alone. It is the purpose of the latter department eventually to publish an illustrated bulletin covering all its in- vestigations. * The report here deals solely with certain interesting discoveries that have been made relating to the method of infec- tion and early development of the bhster rust in the white pine. It can now be definitely stated that infection takes place through the stomata on the needles rather than through the stems or buds as commonly supposed. A preliminary note of this work has already been published by the writers (4 p. 15) in the Report of the Blister Rust Committee for 1918. Previous Investigations. While Dietrick (6 p. 287) as early as 1856 reported both the Peridermium on white pine and the Cro- nartium on Ribes species from Russia, he evidently did not recog- nize that they had any relationship to each other. Klebahn (8 p. XL VIII) in 1888 was the first to prove this relation by inoculations, using the aecial spores from the white pine on the leaves of Ribes nigrum. Later he and other European investiga- tors, and Spaulding (19 p. 244) in America, abundantly verified this relation by the inoculation of a great number of Ribes species in similar manner. When we turn to the inoculation of the white pine with the telial stage from the Ribes, however, thus completing the evidence of their relationship, we do not find that many investigators have reported experimental evidence. In faci:, Klebahn (10 p. 86) in 1905 seems to have been the first and only European investiga- tor to report such successful inoculations (made in 1903). As early as 1890 he (9 p. 62) had attempted inoculations but was doubtful as to the results, as the plants used may have already been infected. While there is no doubt that he did infect two white pines under bell jars in the fall of 1903 (10), by placing in- fected leaves of Ribes nigrum on a wire net over them, unfortunately *This report will be published by the writers and Mr. E. M. Stoddard of this department, who has also co-operated largely with the forestry department in its control work. The wiiters are indebted to him for the photographs and photomicrographs with which this article is illustrated. 432 CONNECTICUT EXPERIMENT STATION BULLETIN 214. he left the pines out doors over winter and did not carefully examine them until the middle of the following June. It was evidently then too late to determine the very first signs of infection and the manner in which it took place. He noted the yellow spots on the previous year's leaves, of which we shall speak in connection with our own experiments, and found the myceHum of the rust in these spots. He also found that two of the yoimg stems were of a paler color, distorted, and bore at first juvenile leaves instead of the normal fascicles of five leaves. In July spermagonial drops began to appear on the infected branches. Concerning the manner and place of infection he seemed in doubt, but makes the following remarks: " The fact that localized yellow spots were present in these needles does not necessarily mean that the mycelium arising through infection in the needle has in especially high degree the power to grow forth in the longi- tudinal direction of the needles, and to penetrate into the branch. Whether the bark of the young branch at the time of the maturity of the sporidia can be pierced by these is likewise doubtful. There- fore it may perhaps be presumed that the fungus can easily pene- trate into the branch if the base of the needle is infected. StiU another possibility is that the sporidia must infect the young buds for the next year." Klebahn further stated in 1918 (11) "For Peridermium strobi it is shown that the needles can become infected but not that the mycehum grows from the needles into the bark." Spaulding (16 p. 147) in January 1912 published the following brief note concerning his inoculations on white pine: "Greenhouse inoculations have been made upon young Pinus strohus with teleutospores secured by inoculation on Ribes americanum with aecidiospores borne upon imported trees of Pinus strobus. Inoculations thus made in November, 1910, are now beginning to give results. One each of the trees inoculated with wounds and without wounds, is now showing slight swelling such as is so characteristic of the bHster rust disease." This statement indi- cates, as Spaulding has recently told the writers, that the inocu- lations were on the stems. He also said that none of the infected pines formed the aecial stage, but the pycnia, with exudation of pycniospores, were produced. From the results of these investigations by Klebahn and Spauld- ing one is left in doubt whether infection takes place through the INFECTION OF PINE WITH BLISTER RUST. 433 leaves, the buds or the stems, ajid in what particular manner. Judging from other statements in literature on this subject, the general impression is given that it takes place through the stems. For instance, Fischer, of Switzerland, (7 p. 435) states: "The aecidiospores infect the Ribes leaves upon which first uredo then teleutospores appear; the latter germinate immediately and infect the young twigs of pines." Spaulding (17 p. 6) says in one of his earlier papers in 1912, concerning infection: ''The winter spores are blown from the currant and gooseberry leaves upon which they are produced to various parts of the white pines in the vicinity. There they stick to the bark of the young trees or branches and germinate. The branching threads of the fungus penetrate the inner bark tissues for some distance, but cause no external sign of disease until nearly a year after the time of infection". He makes about the same statements in his excellent bulletin (15 p. 26) on the "Blister Rust of White Pine" published the year previously, and in 1916 he (18 p. 14) states: "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 in- cubation period already mentioned." Metcalf (14 p. 3) in 1917 makes a similar statement as follows: "The pine blister attacks white pine seedhngs or pines of any age that have needle-bearing twigs through which it can enter. The disease spreads from the twig" etc. McCubbin, also, writes in 1916 (12 p. 1) "It is believed that the fungus gains entrance by some wound in the twigs or branches, and from the point of entrance it grows rapidly up, down and around the branch in the soft outer bark". In an article written in 1917, however, he (13 p. 95) questions the branch method of infection as foUows: "Only indefinite references to the method of infection of the pine by Cronartium ribicola have appeared in current literature. From these references one gathers the impression that infection takes place through the bark, and probably by way of wounds or abrasions. Having an opportunity for studying a considerable number of pine infections in 1916, some attention was given to this point and records were made of the origins of cankers where such origins could be determined. "In most cases the determination was not difficult, owing to the fact that in a healthy pine branch the fungus spreads out from the court of entry in a very legular and equal manner, and that its piogress is marked by swelling or discoloration or both, or else the cortical tissue is killed in 434 CONNECTICUT EXPERIMENT STATION BULLETIN 214. an equally radial fashioa. By taking note ot this habit one can readily locate the point of original infection in most cases, especially in the earlier stages. "Very early in this study it became apparent that the chief mode of infection was by way of leaf fascicles through the so-called short shoots. In these pines, which were all healthy and which grew in situations where they were fairly free from accidents, wound infection played but a very small part. "According to the tabulated results about 92 per cent, of these young blister cankers originate in leaf-bundle infection. This percentage in- cludes only those cases where the point of origin could be confidently established, but it is highly probable that a large proportion of the num- ber listed as undertermined should also find a place here, and it might not be overstepping the mark to ascribe at least 95 per cent, of these blister cankers to leaf fascicle infection. "One may consider that the sporidia from the currant leaves are lodged among the bases of the needles and from this position can then attack the short shoot which bears these leaves." PRESENT INVESTIGATIONS. First Infections. On October 21, 1916, the senior writer placed infected leaves of Ribes nigrum, having the telial stage, over two crocks each containing three two-year old seedhngs and two crocks each containing six one-year old seedlings of Pinus strohus. These were moistened, covered with bell-jars for several days and have been kept in the greenhouse ever since. Nothing suspicious showing during the first month or two, they were not carefully examined thereafter for some time. On June 14, 1917, the writers looked them over critically and in one of the crocks found two of the one year old seedhngs showing conspicuous yel- low spots which were not seen on the leaves of the other plants. These two seedhngs also showed the bark slightly swollen and of a yellowish-green color. On July 14th one of the two year old seedlings, which had shown nothing very suspicious previously, was found to be oozing pycniospores in less than nine months after inoculation. Later a second of these two-year old seedhngs died and microscopic sections showed pycnia. Several of the young seedlings were dead by this time, whether from rust or other causes was not determined. At the present writing two of two-year old and one of the one-year old seedhngs are still ahve, but show no signs of infection. Thus out of 18 plants at least 4 were definitely known to have become infected. *■ INFECTION OF PINE "WITH BLISTER RUST. 435 Sections of the needles through the yellow spots mentioned above showed abundance of mycehum which was also found in the swollen stems and because of this it was uncertain whether the infection had taken place originally through the leaves or stem. It was to settle definitely this point that inoculations in the fall of 1917 were again made. These plants were carefully watched from week to week to obtain the first indications of infection. The results obtained were verified and extended by other experiments made in the fall of 1918. Therefore the data given in the following pages are the combined results of infections made during these three years. Methods of Inoculation. In Greenhouse: Condition of seedlings. Practically all of the pine 'Seedlings used in the experiments have been grown in crocks usually from three to ten in a crock, and have been kept ever since in the greenhouse of the Experiment Station. Some of these have been grown from seed and others were obtained from our own and a nearby nursery where bhster rust has never occurred. No rust either on Ribes or white pines has ever been found in the vicinity of the Station. Therefore there is absolute certainty that any infections that have taken place are the results of our inoculations. Most of the seedlings used have been one, two or three years old, since for convenience and ease of infection these have proved most satisfactory. When we speak of one year old seedlings we mean those of less than a year's growth as they varied in age from four to eight months. Similarly by those two and three years old we mean in their second and third year's development. For the most part these plants have made excellent growth. As they have been kept in the greenhouse the year round they have not had the winter rest period of plants grow- ing outdoors, but during late fall and early winter their growth has been noticeably retarded. Of course where infection has taken place in the fall these plants in late winter and early spring have shown the disease far in advance of those plants infected at the same time but kept outdoors through the winter. This forc- ing of the plants and the disease indoors must be taken into con- sideration, at least as regards time, when comparing with infections that take place in nature. It is evident from these experiments, however, that the rate of development of the disease is correlated with the vigor and rapidity of the growth of the plant. 436 CONNECTICUT EXPERIMENT STATION BULLETIN 214. Preventive measures. Unless it were desired to keep certain parts of the plant from becoming infected, the inoculation material was placed in and aroimd the moistened plants which were kept covered with a bell jar in subdued Hght for several days. Where it was aimed to produce infections through definite parts, care was taken to inclose the inoculation material with damp cotton to prevent the sporidia from escaping, or else the inoculated part was left exposed and all the rest of the plant was protected by dry cotton or paper. Plate XXXVII, fig. 3 shows an example of the latter condition where spores had been placed on the young leafy shoots after the rest of the plant had been covered. Parts inoculated, (a) Stems. The inoculations on the stems were made in two ways : 1st by cutting a slit in the stem and inserting the germinating telial column; 2nd by applying the'telial material to the uninjured stem. In both cases the material on the part inoculated was wrapped with moist cotton. The cotton also served to indicate the place of inoculation later on. The stems used, especially on younger seedlings, were quite small (less than a quarter of an inch in diameter and were one or two years old) except in a few cases where the green stem of the present j^ear's growth on larger plants was used. (b) Buds. By unopened buds we mean the terminal ones and in an entirely dormant condition closely enwrapped with the enveloping brown scarious scales, with no green parts of leaves exposed. By open buds we included those expanded enough to show the developing leaves. In both cases especial care was taken to protect all other parts below from infection by the devices already mentioned. (c) Leaves. With inoculation of leaves usually no particular effort was made to prevent general infection, since infection of the leaf was determined by the appearance of yellow spots. It was always possible through microscopical sections of these yellow spots to find the particular stoma or stomata through which entrance was gained. There were four different methods used: (1) placing infected leaves on the soil of the crock, or (2) over the plants themselves, or (3) still attached to stems stuck in the soil, and (4) sprinkhng water containing telial material over the plants. In some cases attempts were made to inoculate special parts of the leaves as base, centre, or apex, such places being marked by a string tied at the point of inoculation to identify it for later INFECTION OF PINE WITH BLISTER RUST. 437 examination (PI. XXXVII, fig. 2). Again, leaves of different ages were used, as those young and still growing and others one or two years old. Also the juvenile leaves, such as first appear on the seedlings (PI XL, fig. 4) or under exceptional conditions on older plants, were inoculated in comparison with the ordinary leaves which develop in fascicles of fives on the plants after the first year. In Pelrie Dishes. Having been successful with the inoculation of Ribes leaves in moist Petrie dishes (4 p. 14) it was thought that this method might be appKed to the pine needles, at least so far as showing place and method of entrance of the germinating sporidia. Both juvenile and fascicled leaves were used, the for- mer on short shoots or on the entire seedling and the latter un- attached or attached to the stem (PI. XXXVII, fig. 1). Inocula- tions made in 1917 showed no apparent infection though the needles were kept in good condition for a month. Possibly the failure here was due to the fact that the leaves were all of the fas- cicled form and were kept in the diffused light of the laboratory. The next year the experunents were extended to young seedlings and the Petrie dishes this year were kept in the more direct light of the laboratory greenhouse which faces the east and is protected from southern exposure to the sun by a wing of the building. Under Tent. Another method tried was the inoculation of pines under a tent, to approximate natural methods of infection without danger of spreading the spores. The tent was made of unbleached muslin stretched over a frame about four by eight feet and about six feet high at the ridge. A door on one side made the examination of the plants easy at any time. To this tent two black currant bushes had been transplanted to determine if the Cronartium was carried over on bushes infected the previous year. Nothing showing in this respect the currants were arti- ficially inoculated with urediniospores the middle of the summer of 1918. On August 15, after the appearance of the telial stage, a wooden box containing numerous small two year old white pine seedlings was set in the soil under each bush. On October 2, about a dozen plants from each box were transferred in a bunch to crocks in the greenhouse to see if forcing the plants during the winter might have any effect upon the appearance of the (disease. On September 28 a white pine about a foot high and at least five years old was also placed under each infected bush. 438 CONNECTICUT EXPERIMENT STATION BULLETIN 214. Out of Doors. In addition to the preceding, three pines about three or four feet high and six to eight years old growing in a shel- tered spot on the Station grounds, and three trees, fifteen to twenty- feet high and fifteen to twenty years old at the Whittemore estate in Middlebury, Conn., were also inoculated. In the case of the pines at the Whittemore estate there was a possibility of outside infection since Peridermium strohi had been found on certain of these trees. At both the Experiment Station and at Middlebury the method used for inoculation was to spray the branch with water and then to inclose it in a double paper bag in the inner one of which were placed loosely or sewed to the paper fresh Rihes leaves infected with the telial stage. A variation of this method was to spray the leaves with water containing the germinating teliospores before placing the bag over the branch. The paper bags were left on the branches from two to four weeks and in some cases even longer. Except for the longest periods, living in the bags did not seem to injure the leaves to any appre- ciable extent. These experiments at both places were carried on in 1917 and again on other branches or trees in 1918. Altogether in the two years nine branches at the Experiment Station and thirty- one at the Whittemore estate were inoculated. General Results of Inoculation. Out of Doors. Of the forty branches inoculated at the Ex- periment Station grounds and at the Whittemore estate twenty were made each year. Despite these many attempts not a single inoculation was successful so far as can be determined at the present time (July 9, 1919) . Those made in 1917 were certainly old enough to show some sign of infection if successful. Close watch has been kept for indication of yellow spots on the leaves so characteristic of greenhouse infection, without any evidence of the same. Some- what suspicious spots have been sectioned for decisive proof of the presence of the mycelium but also without result. . To some this might indicate that in nature infection does not take place through the leaves, but to the writers it is more of an indication that the methods of inoculation were faulty, since there is no evidence of any infection through the young stems or buds which were equally exposed with the needles. The age of the leaves could not have been the limiting factor, since leaves nearly two years old (about their age limit) were abundantly infected on INFECTION OF PINE "WITH BLISTER RUST. 439 the young trees in the greenhouse. It is uncertain whether these apparent failures were due to rapid decline of the inoculating material after being placed in the bags, to unfavorable conditions of moisture or temperature, or to some other unknown factor. In our greenhouse experiments we have had great variations in results of inoculations due to conditions which we have not always been able to explain. We speak of these outdoor inocula- tions as failures since in the greenhouse experiments some sign of infection visible to the eye has always shown within one to six months after the inoculation if successful. Under Tent. On October 2, at the time of the transference of part of the two year seedlings from the box under the tent to crocks in the greenhouse, no sign of infection was visible on the leaves. On November 8 a single very inconspicuous yellow spot, evident only under the lens, was found on one of the plants in the tent and this on sectioning showed the characteristic mycelial masses. A day or two previous similar spots had been found on four of the plants transferred to the greenhouse. During the winter the seedlings in the tent showed little evidence of further development of the fungus. For example, on February 24 only a few spots were seen on the leaves. These were scarcely visible to the naked eye, being about one-fourth of a millimeter long, directly over the stomates and not encircling the leaf as yet. In comparison with the spots on the plants transferred to the green- house they were very much less developed. On May 24, however, these spots were more numerous and were evident to the naked eye, some of them encircling the leaf while others were scarcely visible. One plant showed fourteen leaves with these spots and the stem had already become invaded. A very large percentage of the plants apparently were infected. Unfortunately a number of the plants had been winter-killed and during June a severe hot period killed most of the remaining ones, only four being alive in July. This greatly interfered with determining just how far advanced these spots on out of door plants would be at this time of the year, but those that were present were not very striking. These experi- ments would indicate that infection in nature, which takes place in the fall, is very inconspicuous and may entirely escape detection at that time, and that the spots develop rather slowly during the spring, perhaps in cases not becoming conspicuous until the middle of July. 440 CONNECTICUT EXPERIMENT STATION BULLETIN 214. On the other hand the plants that were transferred October 2 to the greenhouse continued to develop, at first slowly during the late fall and early winter. By Novenber 26 at least seven out of the fifteen plants in one crock and all eight plants in the other crock showed inconspicuous spots indicating infection. By January 28 the spots were more conspicuous, in cases six to ten showing on a single plant. At this time the spots were one- sixteenth of an inch long and barely encircling the leaf. In one plant a slight swelling and yellowing of the stem indicated infection there had already taken place. From February 20 to the middle of March these spots became quite conspicuous, usually one to four mm. long and entirely encircling the leaf. The average spot was about two mm. long. In cases where infections had taken place close together these golden-yellow spots were merging. By the last of March it was evident that nineteen out of the twenty- three plants transferred had these infections on the leaves and their appearance was in strong contrast to those that had been left in the tent during the winter, showing how the favorable green- house conditions had hastened the development of the fungus. By July 1 the spots were about 2-3 mm. in length, though by merging some were even 6 mm. long. However by this time the spots were past their prime as some of the leaves containing them were dying or drying up. At least one plant was dead and on some of the others the new shoots were killed. It seems evident that, while a few have formed pycnia, none will survive to form aecia. The two large white pines placed in the tent on September 28 on the date of the last examination (July 8, 1919) failed to show any certain sign of infection. If such had taken place the yel- low spots on the leaves have remained obscure. These plants of course were transplanted in the tent much later than the seedlings and were not directly under the bushes, as were the former, so that the conditions for infection were not so favorable. In Petrie Dishes. Of a score or more of inoculations' in Petrie dishes with the pine leaves, both of the fascicled and juvenile forms, we were successful in only two experiments. One of these was on very young seedlings and the other on shoots having juvenile formed leaves. In no case were we able to detect infec- tion on the fascicled leaves. Even on the juvenile leaves the spots were so shght as to require careful inspection with a lens to INFECTION OF PINE WITH BLISTER EUST. 441 determine their presence. Four out of six seedlings in one case showed a few spots which were identified by microscopical sec- tions as containing the rust. Of the five shoots in the other case, infection was positive in two and probably in two more. All these infections were first identified about five weeks after inoculation by which time most of the Petrie dish cultures were usually in poor condition through molds, etc. These spots were first visible somewhat later than the earhest signs found in potted plants in the greenhouse. The length of time required after inoculation before infection shows makes this a rather unsatisfactory method for telial inoculation as compared with the same method for inocu- lation on Ribes leaves. In Greenhouse, (a) Stems. In the two years, inoculations were made on thirty-five cut and fourteen uncut stems and not a single one of these forty-nine cases has shown any evidence that the inoculation was successful. This seems somewhat contradictory to the results obtained by investigators with other species and with the apparent result obtained by Spaulding with this method. We are not certain whether the latter used any precautions in preventing infection through the leaves. We do not wish to state positively that infection cannot take place through the stem, either wounded or unwounded, because we were unsuccessful in our attempts. Possibly the small size of the stems through which we attempted inoculations may have had something to do with the failure. There is no question that on very vigorous green shoots stomata occasionally occur and it is not impossible that the germ tubes of sporidia may gain entrance through them. Their small number and the difficulty of the sporidia sticking to the stem, however, would make the chance of infection slight as compared with that of the leaves. (b) Buds. During the two years inoculations were made on the opened buds of twelve plants, seven of which were successful. On the unopened buds fourteen inoculations were made in 1917 and ten in 1918. Of these only two were successful, both made in 1917, and it is not certain whether these buds can be strictly considered as unopened. Our classification of buds as opened and unopened, too, in 1917 was not so clear cut as in 1918. In one of the plants the permanent sHde shows, by the presence of a definite sclerotial mass some distance from the base, that infec- tion took place through a scale which had become elongated, 442 CONNECTICUT EXPERIMENT STATION BULLETIN 214. green and needle-like. In the other plant evidence is lacking how infection took place as sections were not made until the tissues of the young stem had become thoroughly invaded. From the results of these experiments it seems that infection can readily take place through opening buds or shoots which have exposed leaves containing stomata. On the other hand it seems quite certain that infection does not take place through an unopened bud closely enwrapped by the scarious brown scales. In some cases these scales, however, continue their development into modified leaves and, through the stomata of such, infection no doubt may take place as in the case cited above. (c) Leaves. As has just been noted infection readily took place through the leaves. In fact so far as we can determine of the one hundred successful inoculations reported in Table 6 all, except in the two very doubtful eases already cited, were traceable to leaf infection. The very first sign of infection to the naked eye, visible usually about a month or two after inoculation, or even earlier with a hand lens, is a very small yellowish spot centering in the lines of stomata that run lengthwise of the leaf (PI. XL, fig. 3). These infected leaves later showed evident golden-yellow encircling spots (PI. XL, figs. 1-2) which were filled with character- istic sclerotial masses of the fungus, even when there was no myce- lium in the stem. Eventually, however, it appeared there at the base of these infected leaves. Sections through the yellow spots also definitely proved that infection took place through the stomata- as indicated by a characteristic substomatal vescicle directly below the guard cells. Details of infection and the nature of the substomatal vescicle will be discussed later. Suffice it to say here that there was always found in microscopic sections of the yellow spot, usually about the center and beneath a stoma, a substomatal vescicle with a primary hypha leading down to the sclerotial mass (PI. XLI, fig. 2; PI. XLIII, figs. 1-6). For example, in one leaf nineteen distinct yellow spots were counted and sections of this leaf showed at least twenty-one substomatal vescicles. In some cases the number of infections as indicated by yellow spots was obscured by the latter running together (PL XL, fig. 6) and in a few instances we found two substomatal vescicles below one stoma signifying two infections at this place. So far as types of leaves are concerned infections were secured readily through both the juvenile and fascicled forms. The former INFECTION OF PINE WITH BLISTER RUST. 443 because of their flattened and somewhat grooved upper surface, thereby more readily retaining sporidia, are perhaps somewhat easier infected. As to age we succeeded in infecting leaves from the very young juvenile stage to those of fascicled form one and even nearly two years old. There did not seem to be any difference as to the part of the leaf involved (base, middle or apex) since infection readily took place all over (PI. XL, fig. 1), except that the bases of the leaves may have afforded better chances for the sporidia to adhere. Quite variable results were obtained with different methods of inoculation. The most successful was the one in which the Rihes stems with fresh infected leaves were stuck in the crock over the pines. This method approaches nearest to natural conditions. Of thirty-six plants in eight different crocks inoculated on Oct. 19 and 22, 1918, all but one were infected. Not only was this high percentage of infection secured but the many yellow spots on the leaves showed that the infections had been very numerous on each plant. Of these plants fifteen were three years old and twenty-one were seedlings of less than six months. Infections of the latter was so severe that at the present writing practically all have been killed. Fair results were also obtained where water containing tehal colum.ns was sprinkled over the plants especially those containing young shoots. The poorest results were given where the infected leaves were put on the soil under the pines, only one out of ninety plants becoming infected. Where such leaves were placed over the pines the results were better. Percentage of infection does not alone explain the value of the method employed, since a single plant infected through a single leaf is not comparable to another plant infected through many places on numerous leaves. While the method of infection may have had considerable to do with the results obtained, the time of infection also seems to have been a factor. During the two years, on the whole, the best results were obtained during October. Infections, however, may take place at any time sporidia are produced in good condition, since we infected a plant in one instance in June. Age of Plants. Out of two hundred and thirteen plants inocu- lated in 1917, one hundred and thirty-three were one year, and eighty were two j^ears old; and of the twenty-four resulting infections eighteen were one year and six two-year old pines. In 444 CONNECTICUT EXPERIMENT STATION BULLETIN 214 . I 1 Table VI — Geeenhousb Inoculations Inf. Ribes Inf. Ribes Inf. Ribes Total Total inf. Inf. Ribes leaves leaves on soil branches in soil Date No. plants inoc. leaves on soil. over plants. and over plants and spreading over plants. No. No. No. No. No. No. No. No. No. per cent. inoc. inf. inoc. inf. inoc. inf. inoc. inf. 1916 Oct. 21 18 4 22 18 4 1917 Aug. 25 21 0 0 16 0 Aug. 27 9 0 0 Sept. 6 57 3 5 32 '6 ie '3 Sept. 12 11 0 0 Sept. 14 5 0 0 '5 '6 Sept. 24 9 0 0 9 0 . . Oct. 15 21 4 19 10 1 Oct. 16 8 4 50 Oct. 17 61 13 21 Nov. 1 11 0 0 ii 0 • • Total... 213 24 11 83 1 0 0 16 3 0 0 1918 June 13 1 1 100 , Sept. 30 12 0 0 7 '6 '5 '6 Oct. 1 48 9 19 Oct. 2 6 3 50 Oct, 5 11 1 9 ii 'i Oct. 7 4 1 25 Oct. 8 to 2 20 Oct. 9 18 6 33 9 3 '2 i Oct. 10 5 2 40 2 0 Oct. 11 35 10 28 Oct. 19 28 28 100 28 28 Oct. 22 8 7 87 8 7 Oct. 26 2 2 100 Oct. 29 2 0 0 Oct. 30 3 0 0 "3 '6 Total. . . 193 72 37 7 0 14 3 18 2 36 35 Total for3yrs. 424 100 23 90 1 14 3 52 9 36 35 1918 of the one hundred and nmety-three pines inoculated (not including the twenty-three inoculated in tent and later transferred to greenhouse) fifty-eight were one year, thirty-six two years, and ninety-nine three years old. This year seventy-two plants became infected, twenty-nine of the one year, four of the two years and thirty-nine of those three years old. While these embraced the Yl irious met hods 0 fir lOCl ilat ionj th ey wei -e E LOt exa ctly th le 3am e i - INFECTION OF OP Cronariium PINE WITH ribicola on BLISTER RUST. Pinus sirobus. 445 III spores on def. spots on pine leaves III spores sprayed over plants. III spores sprayed over young shoots. III spores on Buds. III spores on Stems. opened. unopened. cut. uncut. 1 No. 1 inoc. No. inf. No. inoc. No. inf. No. inoc. No. inf. No. inoc. No. inf. No. inoc. No. inf. No. inoc. No. inf. No. inoc. No. inf. 6 3 3 6 '8 19 0 0 0 0 °4 0 2( ) 9 '5 "5 '3 '2 '3 6 '5 '6 0 2(?) '3 '5 '3 i2 '6 '6 '6 '6 3 6 \ 44 4 20 9 0 0 10 5 14 2(?) 23 0 3 0 1 2 2 3 2 3 3 4 0 2 2 0 1 i2 '4 2i "2 2 1 5 1 5 2 0 3 2 3 3 2 3 2 2 '4 "4 '2 '6 '6 '0 ] [ ) ) ) 8 3 6 6 33 8 42 14 8 8 2 2 10 0 12 0 11 0 77 12 62 23 8 8 12 7 24 2(?) 35 0 14 0 i f( a y ti 0 p )rt ffec ear on. f th er ( rere he tec th I e c 3en m difl I s e c ^or )ne t.c uc 'er on ne in y fi ti ] ent lew -ye stai 3ar, :he tiigl a h£ ai ac e i\ le ges It b 'olc e, ir leve iree r th of y I] i] n y ai the the pine L918 per ears 1 th P r s k ,0 ce 0] OS inee net ^av ftl: nt. db e 0 > u tio 3 t le of ec sed ds he ino th am line and g emplc highe 3ulate 3 two 3 infe( d in 0 the >yed. st per d plar years 3ted. 1917, res H cer its an TI wl 5Uli 'o\^ ita fifl di les len :s T fev ge ^yi .hii ep or vol er, of 3er 'ty er iiy lie € in c -e ce f ibe ach fec- ent. ight nts. our- 446 CONNECTICUT EXPERIMENT STATION BULLETIN 214. teen per cent, of the one year and eight per cent, of the two years old were infected. In 1918 the conditions for securing infection were much improved by the use of infected Ribes leaves still attached to the branches, as one of the methods of inoculation, and by the presence on many of the three years old pines of new shoots, some of which had juvenile-formed leaves. For examples of abundant infections resulting, two hundred and eighty-four yellow spots were counted on thirty-eight leaves of a year old seedling; and one of the three years old pines showed fully as many similar spots on the fascicled leaves. The counts in the former case were made before it was apparent to the eye that the stem was invaded. The young growing seedlings and vigorous growing older plants, especially the younger parts, seem to take infection better than plants that are at a stand-still or somewhat sickly. This appears to be true of bright, dark green leaves as compared with those more or less speckled and not of so healthy a color. Pycnia and Aecia. There is no question that the younger a seedling is when infected the less chance it has of survival. This is especially true of the very young seedlings, most of which failed to survive a year or even long enough to form the pycnial stage. The new shoots of the older plants, especially where infection took place through their juvenile form leaves, were often dead by the following summer. The number and place of infections, together with the vigor of growth, largely determine the hfe of the infected pine. Pycnia of the normal type and oozing pycniospores have appeared on a number of these infected pines even including some of those classified as one year old seedlings. The pycnia have been seen four months after inoculation but usually it was five or six months before pycnial drops appeared. Vigorously growing infected stems, when oozing pycnia, are especially sub- ject to attack by chewing animals, apparently slugs, which con- ceal themselves in the damp soil of the crocks. This has no doubt interfered somewhat with the further development of the rust. In no case yet have aecia appeared on any of the infected plants. Of those infected in 1917 only five remained alive in February, 1919. They were the older and larger plants and it seemed quite possible that aecia might appear on them during the spring. However, by July, they had all been killed by the rust without its further development. Up to date none of the plants infected in 1918 has shown any signs of aecia, though producing INFECTION OF PINE WITH BLISTER RUST. 447 pycnia. However, as a number of these are of the largest size used and apparently growing vigorously, despite the evident infection, there is a possibility that they may produce aecia in 1920. See Table 6 for further details of greenhouse infection. Other Species Inoculated. During 1917-18 besides Pinus strohus four other five-needled species were inoculated, partly out-of-doors and partty in crocks in the greenhouse. Of these Pinus excelsa was inoculated nine different times; Pinus flexilis, three different times on five differ- ent branches; Pinus cembra, once on two different plants; and Pinus koraiensis, two different tunes on three separate branches. Inoculations with Pinus excelsa were all, except in two cases, in the greenhouse. The greenhouse plants were four and five years old, while the out of door plant, used both years, was about six to eight years old. The other three species were all out of door plants of the same age. Despite the fact that the rust has been reported on some of these hosts we did not in a single instance secure an infection. Purely as a matter of curiosity, as successful results were not expected, inoculations were also attempted one or more times on the following two needled pines, all of which except Pinus densiflora were grown in crocks in the greenhouse : Pinus austriaca, P. densiflora, P. resinosa and P. sylvestris. In the case of Pinus sylvestris, five one-year old seedlings were used, as such young plants are most likely to become infected, if susceptible. As in the preceding species, none of these inoculations was successful. DETAILS OF LEAF INFECTION. Telia and their Germination. As already stated, the telial or III stage of the fungus may be formed on the Ribes leaves (PL XXXVIII, fig. 1) any time of the year from June on, although in nature they usually begin to appear the latter part of July and are most conspicuous in September and October, They develop more or less thickly on the under side of the leaves as short hairy growths about one or two mm. in length (PI. XXXVIII, figs. 2-3). As seen individually under the microscope the reddish-brown telial hairs (PL XXXVIII, fig. 4) are found to be composed of a 448 CONNECTICUT EXPERIMENT STATION BULLETIN 214. solid column of spores. These spores are considerably elongated lengthwise of the column, although at the ends they are shorter and broader. The more cylindrical ones (PL XXXIX, fig. 1) are 37- 60yu X 14-16/^ while the shorter apical ones are usually 27-36yw x 18-21yu. Longitudinal sections show that they are formed in chains, those of the interior adhering more loosely together, but often breaking joints so that the telial column is rather permanent although with pressure it may separate into chains or single cells (PI. XLIV, figs 1-2). CoUey (5 p. 637) gives a comprehensive description of the telia in his excellent paper on the microscopic structure of the blister rust, so that further details are omitted. The telial spores germinate, in situ, anytime after maturity when conditions are favorable (PI. XXXVIII, figs. 5-6). Apparently each spore may give rise to a pro mycelium which is sent out from its side as a growth filled with protoplasm, ordinarily reaching a length about that of the spore (PI. XXXIX, figs. 1-2). This promycelium soon is divided by septa into four uninucleated fertile cells filled with protoplasm and a semi-empty basal cell. (PI. XLIV, figs. 5-6). From each of the fertile cells (PI. XXXIX, fig. 3; PI. XLIV, figs. 7-10) arises a prominent pointed sterigma about the length of the cell. When fully developed, the sterigma forms at its tip (PL XXXIX, fig. 4) a swelling into which as it grows passes the entire protoplasm and the nucleus of the cell, forming a spherical sporidium about 10-12yu in diameter (PL XXXIX, fig. 5). The sporidium when mature, is easily separated from the narrowed tip. Variation from the normal type of germination of the telia is shown where instead of a promycelium a mycelial-hke thread is formed (PL XLIV, figs 11-12). Another abnormal type is shown when the cells of the promycelium round up and become separated as kind of sporidia-like bodies (PL XLIV, fig. 13). These variations are probably produced under unfavorable con- ditions of aeration such as are often obtained in van Tieghem cell cultures. The sporidia are comparatively short-lived and germinate immediately under favorable conditions of moisture. Usually a single germ tube is sent out (PL XXXIX, fig. 6; PL XLIV, fig. 16) tapering somewhat towards the tip. In cultures this germ tube may reach a length several times that of the spore and may be more or less curled (PL XLIV, figs. 18-19) and rarely gives rise to a short branch (PL XLIV, fig. 22). Occasionally sporidia are found INFECTION OF PINE WITH BLISTER RUST. 449 which have two or three germ tubes developing (PI. XLIV, figs. 15, 17, 21, 22). Often a sporidium instead of forming an infection tube gives rise to a tapering sterigma about twice its length, on the tip of which is produced a secondary sKghtly smaller sporidium (PL XXXIX, fig. 7; PI. XLIV, figs. 23-25). As apparently only a single one is produced, this formation of a secondary sporidium is probably to tide it over unfavorable conditions of infection. These data were obtained partly from the germinating telia in situ and partly from those placed in watch crystals and van Tieghem cells. Infection through Stomata. When a sporidium is blown to a leaf no doubt it germinates in the manner as described above by sending out a germ tube. Contrary to the general belief this does not penetrate the epidermis but gains entrance through a stoma. So far it has not been possible to verify this statement by a direct microscopical examination showing the sporidium germinating on the outside of the leaf and the germ tube pushing between the guard cells of the stoma into the air chamber beneath. The reasons for this are that not sufficiently young infections, those less than a week old, have been examined, and the exceedingly great difficulty in locating points of infection, since there is no external evidence to guide one within three or four weeks after this takes place, by which time the delicate sporidium and its germ tube outside the stoma are obHterated. The indirect evidence, however, is sufficient to prove that the germ-tube of the sporidium passes down between the guard cells of a stoma. The youngest stages in which we have been able to find infection was fifteen days after the sporidia had been placed upon the leaves. In this, as well as in numerous older stages where yellow spots indicated the general point of infection, there was always evident just beneath the guard cells (PI. XLI, fig. 1) a characteristic substomatal vescicle, mention of which has al- ready been made. We have never seen in any of our sections evi- dence that the germ tube penetrated directly through the cuticle into or between the epidermal cells. In fact we do not recall having seen any hyphae in the epidermal cells. On the other hand whenever we have sectioned a leaf through a small yellow spot, we have been able to obtain at least under one stoma the substomatal vescicle. This substomatal vescicle we consider to be an inflation of the germ tube immediately it has passed the guard 450 CONNECTICUT EXPERIMENT STATION BULLETIN 214. cells into the air chamber. There is always a beak-like elongation passing from the upper end of the vescicle and often projecting quite up to the central bulge of the guard cells (PL XLIII, fig. 6) where evidently the germ tube entering into the leaf becomes most constricted and is most likely to be severed. Suhstomatal Vescicles. A substomatal vescicle is a character, istic swelling of the mycelial thread never found except just beneath a stoma. As already stated it always ends above in a short beak projecting up between the guard cells. This beak (PI. XLIII, figs. 1-6) varies from 2 to 22m in length according as the section passes directly through the centre of the substomatal vescicle or to one side. It ends in a sharp point where the guard cells approach nearest together and below joins directly to the centre of the substomatal vescicle by a base about the usual width of a hypha. The substomatal vescicle in general is ovate to ellipti- cal and is elongated in the direction toward the stomal pore. The general size of the vescicle is about 7-11m by lO-lSyw. This sub- stomatal vescicle at least at first is filled with protoplasm, and has a single nucleus (PL XLIII, figs. 1-3). The beak and waU of the vescicle often become somewhat thickened. Primary Hyphae. From the lower end of the substomatal vescicle there develops a thread (PL XLIII, figs. 1-5) about 2.5 to 3.5m wide which usually grows straight down toward the base of the air chamber. Sometimes it turns to one side and comes in contact with the parenchyma cells there, thus forming a shorter tube. This we call the primary hypha because it is the first representation of the mycelium within the leaf and is distinguished from the other hyphae in the immediate vicinity by its compara- tively straight and rarely septate tube. Accordingly as it first comes in contact with parenchyma cells at the side or base of the air chamber, we have found it to vary from 9 to 40/' in length. Once it comes in contact with a parenchyma cell a branch pro- ceeds from its side and by the narrow penetrating tube enters within the cell to form the characteristic finger shaped haustorium (PL XLIII, fig. 1). A source of food supply now being assured secondary hyphae of the mycelium as described later are formed. With the penetration of the aecial and uredinial spores through the stomata in Ribes we have found a swelling outside the stoma as well as beneath it. Whether or not such a swelling occurs in the germ tube of the sporidium on the pine we cannot state. INFECTION OF PINE WITH BLISTER RUST. 451 We have interpreted these external swelHngs (appressoria) not only as hold fasts but also as reservoirs of food for favoring suc- cessful and rapid entrance into the leaf. Likewise the sub- stomatal vescicle not only acts as a hold fast which would prevent the germ tube from being pulled out through the stomatal pore because of greater width but also as a storehouse of food for the rapid development of the primary hypha. Mycelium. The primary hypha having formed a haustorium begins the development of the myceHum. This (PL XLIII, figs. 4-5) differs from the primary hypha by the curled character of the threads which are also frequently branched and septate. The cells of the mycelium are usually much longer than wide, though in this respect there is considerable variation. Usually they vary from 2 to Qm wide by 16 to 21 /U long. The greatly branched and curled hyphae (PI. XLIII, fig. 6) soon begin to form compact masses in which it is impossible to trace the in- dividual threads. In the meantime some of the hyphae have penetrated the host cells by haustoria. Haustoria. The haustoria enter the host cells by a very nar- row penetrating tube which bores through the cell wall and after gaining entrance into the cell assumes its normal diameter of about 3 or 4yw. In general the haustoria (PL XLIII, fig. 4) are enlongated, finger-like bodies filled with protoplasm and may reach a length of 50/^ or more. In the leaf two nuclei have been noted in one haus- torium, though in the stem the haustoria are uninucleate. The usual tendency of the haustorium is to extend toward the center of the cell where the nucleus is situated. There seems to be a sort of attraction by the nucleus since the haustorium frequently forms an abrupt bend (PL XLIII, fig. 6) and partially encircles the nucleus or makes a depression in it, but apparently does not penetrate its membrane. The haustoria usually are simple but occasion- ally have one or two branches (PL XLIII, fig. 7 j) which may be more or less curled and mycelium-like with an occasional septum. Sclerotta. The curled hyphae eventually form a very compact cellular mass much like sclerotia (PL XLIII, fig. 7m). The chief differences between these and typically free sclerotia consist in their greater variation in size and shape, and the lack of any dif- ferentiated bounding layer. The appearance of these sclerotial masses varies largely according as the section of the leaf is trans- verse or longitudinal. In the former (PL XLII, fig. 1) they are 452 CONNECTICUT EXPERIMENT STATION BULLETIN 214. much like normal isolated sclerotial bodies though frequently there seems to be some coalescing of separate masses. In general they are nearly spherical but with occasional irregularities due to coalescence. The size of the sclerotia depends upon their age. Three months or more after infection, with the yellow spots on the leaves very conspicuous, they may extend from epidermis to epidermis and destroy the substomatal vescicle, the evidence of the point of infection. Some of the larger sclerotia thus reach 400/^ in diameter. They begin their development in the inter- cellular spaces causing pressure against the host cells, and such ceUs being enclosed in the sclerotial mass are finally disintegrated though occasional traces of them may be detected. Distortions of the vascular system and other tissues of the leaf may be seen as the result of this exaggerated growth of the mycelium. The color of the yellow spots as seen by the naked eye is due to the destruction of the chloroplasts in the cells of the host rather than to any pigment in the walls or protoplasm of the fungus. The par- enchyma cells immediately surrounding the sclerotial masses contain chloroplasts with a sickly yellowish appearance. In other words the endochrome evident in the mycelium du'ectly producing the spore stages is not found here. In longitudinal sections (PI. XLI, fig. 3) the sclerotia more fre- quently have the appearance of a compound structure or of in- dividual sclerotia running together. This is due to the laminate structure of the leaf, as seen in longitudinal sections, where the fun- gus forms individual masses in the various intercellular chambers and eventually coalesce through continued growth. The function of these sclerotia is somewhat in doubt. It was first thought that they might be the beginning of the pycnial stage, but no evidence of the development of pycnia on the surface of the leaf above them has ever been seen. The fact that they be- gin their development in the fall and that in the fully matured and old sclerotia in midsummer there is some evidence of slight dis- integration of the internal cells, leads us to believe that they act as storehouses to insure the penetration of the fungus through the vascular system of the leaf into the stem. The stem penetration at times may prove a slow process especially when the point of infection is near the tip of the leaf. In such a case the fungus in the sclerotial stage may remain more or less quiescent during the winter and the final penetration of the stem be delayed until the INFECTION OF PINE WITH BLISTER EUST. 453 next spring or early summer. Such a sclerotial mass would in- sure final penetration much more certainly than a slight mycelial growth. Invasion of Vascular Region. Once a sclerotium is developed in the tissues of the leaf it may encroach on the vascular system; that is, while the sclerotium at first is entirely in the mesophyll, it may eventually break through the endodermis (PI. XLII, fig. 2) and be partially enclosed by the same. As sections are taken be- low the yellow spots the sclerotium gradually fades out of the region of the mesophyll and becomes hmited to larger or smaller sclerotial masses in the parenchyma of the vascular region. Very soon all evidence of sclerotium and mycelium disappears from the mesophyll. Haustoria may invade the endodermal or paren- chymatous cells of the vascular region. If the sclerotial masses reach the xylum side of the bundle small sclerotial masses or mycelial strands gradually find their way to the phloem. Sections through the perfectly green leaf some distance below the yellow spot of infection now show the fungus entirely limited to this position within the vascular system. In cross sections of the leaf made still further down it is found that the mycelial strands become very limited in number, seldom branched and grow almost entirely in the longitudinal direction toward the base of the leaf on the phloem side of the bundle. If a single point of infection happens to occur near the tip of the leaf and sections are thus made far. below it, it is almost impossible to distinguish the fungus (PL XLII, fig. 3) from the phloem smce the hyphae in cross sections are so similar in size (3-5 A<), shape and staining as scarcely to be differentiated from the smaller phloem cells. In the larger phloem cells haustoria have been seen and in some of the smaller ones their contents sometimes look like mycelial strands. Invasion of the Stem. As the mycelial strands, running length- wise in the needles in contact with the phloem, reach the base of the leaf, they begin to go out again between the cells of the meso- phyll which in this region, however, is not so definitely marked off by the endodermis. Growing beyond the endodermal cells the fungus finally reaches down into the cortex developing haustoria abundantly in the host cells as it proceeds. Once within the stem the mycelium grows uniformly throughout the bark and causes a stimulus in its growth. This is manifested in seedlings of one to three years old by slight swelling of the stem and upon the green 454 CONNECTICUT EXPERIMENT STATION BULLETIN 214. yoimger parts by a general yellowish discoloration, these being the first evidence to the naked eye of stem invasion. Only rarely, however, have we found a distinct discolored spot on the stem at the base of the leaf fascicle through which the infection took place. The mycelium now becomes very abundant in the young tis- sues of the stem. If the infected leaf happens to be situated on a stem a year or two old invasion is not so rapid or prominent to the naked eye as when it is situated on green parts of a very young growing stem. Entrance here seems to be almost certain death to the terminal parts before the end of the summer. Heavy infection of the stem before the leaves have made their full growth causes a stunting and bunching of the same (PL XL, fig. 5), a characteristic which is employed in plantation or seed-bed in- spections for identifying the fungus before the appearance of its fruiting stage. In very young stems the swelling and discolora- tion may be accompanied by a bending of the terminal part (PI. XL, fig. 4). Heavy infection through many leaves checks in part the later development of the fungus, since the invaded shoots may be killed before the fruiting stages are formed. However, if this is only a lateral shoot, or if the plant is of some size the fungus may yet form its fruiting stage elsewhere. In none of our sections have we found that the mycelium directly invades the growing point, it usually being some distance below where the cells have about reached their normal size. We have occasionally seen cases where the fungus evidently went up from the invaded stem into the new leaves situated on it and at the base of these, or even isolated a short distance above, formed yellow spots quite similar to those of the primary in- fections made through the stomata. Such spots seen late in the season might possibly be mistaken for original infection areas. We are not sure, either, that primary infections may not occasion- ally form secondary isolated yellow spots on the leaves below the point of entrance. We are certain, however, most of the yellow spots that have appeared on our infected plants are primary in- fection areas, even when many showed in a leaf, since thej^ have appeared simultaneously a comparatively short time after the infection took place. INFECTION OF PINE WITH BLISTER RUST. 455 Appearance of Pycnia and Aecia. While we cannot state, from our experiments, the time of the development of the pycnia in outdoor infections, we presume that this usually takes place sometime during the early summer succeeding the fall infection, since this was the case with Klebahn's experiments (9). In our greenhouse infections however they have shown as early as Febru- ary, and on young stems of sufficient diameter have formed slightly elevated yellowish and eventually reddish-brown areas similar to those occurring in nature. On these evident pycnial drops with normal pycniospores have appeared. Preceding development of pycnia microscopical sections show an exaggerated development of mycehum in the cortex sHghtly below the epidermis and from this mass are developed the erect, closely packed, fertile, pycnial threads, from the ends of which are abstricted the pycniospores as has been described in detail by Colley (5 p. 629). In nature the aecial stage develops from more deeply imbedded sclerotial masses in the year following the appearance of pycnia. Unfortunately in none of our indoor infections has this stage been produced, so that details of the time and manner of its appearance cannot be given here. Cycle of Development. From the sum total of our observations and experiments we may summarize the development of the fungus as follows: 1st year. Infection occurs from late summer to late fall through the leaves, producing at most very inconspicuous yellowish spots at the point of invasion. In rare cases it may be that these spots develop more conspicuously and invasion of the stem takes place before winter sets in. £nd year. During spring and early summer the yellow spots on the^^leaves become more or less conspicuous; later there is inva- sion of the stem causing slight swelling and discoloration and possibly in certain cases pycnia are produced. Srd. year. There is further swelUng of the stem and possibly stunting of the leaves with pycnial development during the summer or (in case pycnia were found the previous year) with aecial for- mation in the spring. 4th. year. There may be formation of aecia. In cases of slight or localized infection, especially in hardened tissues, it may be that the formation of pycnia and aecia is delayed for even a longer time. 456 CONNECTICUT EXPERIMENT STATION BULLETIN 214. LITERATURE CITED. 1. Clinton, G. P. Heteroecious Rusts. Ann. Rep. Conn. Agr. Exp. Sta. 1907-08: 394. My. 1908. 2. Clinton, G; P. Pine-Currant Rust, Cronartium rihicola Waldh. Ann. Rep. Conn.Agr. Exp. Sta. 1909-10: 730-733. Je. 1911. 3. Clinton, G. P. Pine-Currant Rust, Cronartium rihicola Waldh. Ann. Rep. Conn. Agr. Exp. Sta. 1912: 347-348. My. 1913. 4. Clinton, G. P. Artificial Infection of Ribes Species and White Pine with Cronartium rihicola. Rep. White Pine Blister Rust Control. Amer. Plant Pest Com. : 14-15. 1918. 5. CoUey, R. H. Parasitism, Morphology, and Cytology of Cronartium rihicola. Journ. Agr. Res. XV: 619-659. 23D. 1918. 6. Dietrich, H. A. Blicke in die Cryptogamenwelt der Ostseeprovinzen. Arch. Naturk. Liv-. Ehst-Kurl., II, 1:287. 1856. 7. Fischer, E. Die Uredineen der Schweiz: 435. 1904. 8. Klebahn, H. Weitere Beobachtungen iiber die Blasenroste der Kefern. Ber. Deut. Bot. Gesell. 6: XLV-LV. 1888. 9. Klebahn, H. Ueber die Formen und den Wirthswechsel der Blasen- roste der Kiefern. Ber. Deut. Bot. Gesell. 8 : (59)-(70). 1890. 10. Klebahn, H. Kulturversuche mit Rostpilzen. Infektion von Pinus strobus L. mittels Cronartium rihicola Dietr. und Rlickschlage zur Jugendform bei Kiefern. Zeitschr. Pflanzenkr. 15: 86-92. 1905. 11. Klebahn, H. Peridermium Pini (Willd.) Kleb. und seine tjber- tragung von Kiefern zur Kiefern. Flora 111-112: 194-207. 1918. 12. McCubbin, W. A. The White Pine Blister Rust in Canada. Soc. Prot. Plants. Rep. 1915-16: 1-8. 1916. 13. McCubbin, W. A. Contribution to our Knowledge of the White Pine Blister Rust. Phytopa'th. 7: 95-100. Ap. 1917. 14. Metcalf, H. The Pine Blister. Introduction Conser. Com. N. Y, Bull. 15: 1-18. 1917. 15. Spaulding, P. The Blister Rust of White Pine. U. S. Bur. PI. Ind. Bull. 206: 1-88. 22 Jl. 1911. 16. Spaulding, P. Notes upon Cronartium rihicola. Science, N. S. XXXV: 146-147. 26Ja. 1912. 17. Spaulding, P. Two Dangerous Imported Plant Diseases. U. S. Dep. Agr. Farm. Bull. 489: 1-29. 1912. 18. Spaulding, P. The White Pine Blister Rust. U. S. Dep. Agr. Farm. Bull. 742: 1-15. 9Je. 1916. 19. Spaulding, P. and Gravatt, G. F. Inoculations on Ribes with Cronar- tium rihicola Fischer. Science XL VI: 243-4. 7S. 1917. EXPLANATION OF PLATES. Plate XXXVII. Methods of inoculating leaves of white pine with blister rust, Cronar- tium rihicola. Fig. 1. Inoculated fascicled leaves in a Petrie dish. INFECTION OF PINE WITH BLISTER RUST. 457 Fig. 2. Leaves inoculated at definite points, marked by strings, under battery jar. Fig. 3. Young terminal shoots inoculated under bell jar, parts below pro- tected by covering of cotton and paper. Plate XXXVIII. Telial stage of the blister rust on currants. Fig. 1. Ribes nigrum with telial stage on under surface of leaf. Slighth' reduced. Fig. 2. Same as fig. 1, showing portion of leaf surface slightly magnified and telial columns quite evident. Fig. 3. Portion of fig. 2, still more highly magnified, about 7 diameters. Fig. 4. Two telial columns, dimly showing cellular structure, extending from fragment of leaf at base. Magn. about 70 diam. Figs. 5-6. Portion of telial columns sending out germ threads; fig. 6 also showing a fully developed promycelium with sporidia. Magnified about 135 diams. Plate XXXIX. Photomicrographs of the development of the promycelium from telial spores. All magnified about 760 diams. Fig. 1. A single telial spore sending out a germ thread, the beginning of the promycelium. Fig. 2. A nearly fully grown promycelium growing out of a cell of the telial column. Fig. 3. Similar to fig. 2, but with promycelium septate and a single ster- igma developed. Fig. 4. Similar to fig. 3 but sterigmata forming young sporidia on their tips. Fig. 5 An isolated promycelium with two empty fertile cells bearing fully developed sporidia, the other two filled with protoplasm and just starting the formation of the sterigmata, and the empty sterile basal cell. Fig. 6. Sporidia just starting to germinate. Fig. 7. A sporidium germinating and forming a secondary sporidium. Plate XL. Infected leaves and seedlings of white pine from greenhouse inocula- tions showing characteristic golden-yellow spots, etc. Fig. 1. Fascicled leaves taken from a pine (No. 623) about 10 months after inoculation, showing a few of the several hundred infection spots that developed within four or five months after the inocula- tion. Slightly reduced. Fig. 2. Juvenile leaves from an inoculated pine showing single infection spots. Slightly magnified. Fig. 3. Leaf showing origin of very young infection spots directly over stomatal rows. Magnified about 18 diams. 458 CONNECTICUT EXPERIMENT STATION BULLETIN 214. Fig. 4. Intected seedling pine with juvenile leaves showing swelling, dis- coloration and bending of invaded terminal shoot. Fig. 5. Artificially infected pines showing bunching and dwarfing of young fascicled leaves. Fig. 6. Pine leaf showing how partially developed, closely-placed infec- tion spots may run more or less together. Magnified about 12 diams. Plate XLI. Photomicrographs of cross and longitudinal sections of infected pine leaves, a-e, host cells; f-i, fungous cells :-a. epidermis, b. stoma, c. guard cells, d. cells of mesophyll, e. vascular system, f. substomatal vescicle, g. primary hypha, h. mycelium, i. sclerotium. Fig. 1. Cross section showing a substomatal vescicle and primary hypha beneath a stoma, and further in fragments of the mycelium out of focus. Magnified about 400 diams. Fig. 2. Portion of fig. 1, more highly magnified, about 800 diams. Fig. 3. Longitudinal section showing sclerotial masses on either side of vascular system. Magnified about 60 diams. Plate XLII. Photomicrographs of cross sections of infected pine leaves, showing leaf structure and sclerotial stage of rust. Magnified about 120 diams. a-e, host-cells; f-g, fungous cells :-a. epidermis, b. mesophyll; c. endoder- mis, d. phloem side of bundle, e. xylem side of bundle, f. sclerotial mass of rust, g. vascular invasion threads. Fig. 1. Sclerotial mass of rust in mesophyll to one side of vascular sj^stem. Fig. 2. SclerotipJ mass within endodermal sheath of vascular system. Fig. 3. Mycelium of rust limited to a few invasion threads on phloem side of bundle shown bj' the darker stained cells. Plate XLIII. Cross sections of infected leaves of Pinus strobus. Magnified about 450 diams. a-f, host cells; g-m, fungous cells:-a. epidermis, b. stoma, c. guard cells, d. cells of mesophyll, e. chloroplasts, f. nucleus, g. substomatal vescicle, h. substomatal beak, i. primary hypha, j. haustorium, k. myce- lium, 1. nucleus, m. sclerotium. Fig. 1. Section of leaf showing a stoma with a substomatal vescicle below it and a haustorium developed from the primary hypha. Int. no. 617 (2); inoculated Oct. 11, 1918, killed Nov. 8, 1918. Slide 11/8/18/ (2). 2. Fig. 2. Section of leaf showing a stoma with a substomatal vescicle having an elongated beak and the straight primary hypha. Pine inoculated Oct. 8, 1918, killed Nov. 9, 1918. Slide ll/9/l8. 2. Fig. 3. Section cf leaf showing a stoma with substomatal vescicle cut somewhat diagonally and the long primary hj^pha. Inf. no. 617 (2); inoculated Oct. 11, 1918, killed Nov. 19, 1918. Slide 12/19/18/ (1).3. INFECTION OF PINE WITH BLISTER RUST. 459 Fig. 4. Section of a leaf showing a stoma with a substomatal vescicle below it and the primary hypha in contact with a host cell and developing mycelium. Inf.no. 617 (2); inoculated Ocl. 11, 1918, killed Nov. 19, 1918. Slide 12/l9/l8/(l). 1. Fig. 5. Section of leaf showing part of a stoma with a substomatal vescicle beneath and the long primary hypha ending in curled hyphae encircl- ing a host cell. Inf. no. 617 (3); inoculated Oct. 11, 1918, killed Dec. 19,1918. Slide 12/19/18 (2). 3. Fig. 6. Section of a leaf showing a stoma and a substomatal vescicle with a very much shortened primary hypha and a well developed myce- lium. Inf. no. 626; inoculated Oct. 19, 1918, killed Jan. 6, 1919. Slide 1/6/19 (3). 3. Fig. 7. Section through a small sclerotial mass in a pine leaf. Inf. no. 624 (2); inoculated Oct. 19, 1918, killed Dec. 17, 1918. Slide 12/17/ 18 (4). 16. Plate XLIV. Drawings of fresh material of telial stage. Figs. 1-2, 6, 11-13, magni- fied about 450 diams.; figs. 3-5, 7-10, 14-25, magnified about 650 diams. a. nucleus of teliospore, b. germ tube of teliospore, c. sporidium, d. fertile cells and e. sterile basal cell of promycelium, f . germ tube of sporidium, g. secondary sporidium, h. sterigma. Fig. 1. Part of chain of teliospores taken from middle of column. Fig. 2. Part of chain of teliospores taken from apical end of column. Fig. 3. A teliospore with a single germ tube starting to form the promy- celium. Fig. 4. A teliospore with two germ tubes starting. Fig. 5. A fully grown promycelium with four fertile cells and one sterile basal cell. Fig. 6. A promycelium with cells starting to form sterigmata. Fig. 7-10. Promycelia with mature sterigmata and sporidia in various stages of development; some of the fertile cells not yet germinating. Figs. 11-13. Unusual types of germination of telial spores — showing in fig. 11a branched germ tube, in fig. 12 a simple wavy germ tube, and in fig. 13 the fertile promycelial cells rounding directly into sporidia- like bodies. Figs. 14-25. Sporidia in different stages and types of germination; 14, 15, 17, 21, 22, sporidia with. more than one germ tube; 16, 18, 19, 20, sporidia with single germ tubes; 23-25, sporidia forming sterigmata with secondary sporidia. PLATE XXXVII. Fig. 1. 1 4 ' 'it- - , } Fig. 2. Fig. 3. METHODS OF INOCULATION. PLATE XXXVIII. Fig. 1. Fig. 3. Fig. 5. Fig. 6. TELIAL OR III STAGE ON RIBES. PLATE XXXIX. Fig 2. Fig. 4. Fig. 5. Fig. 6. Fig. 7. GERMINATION OF TELIAL STAGE. PLATE XL. Fig. 5. Fig. 6. INFECTED PINE LEAVES AND STEMS. PLATE XLI. Fig. 3. CROSS AND LONGITUDINAL SECTIONS OF INFECTED PINE LEAVES. PLATE XLII. Fig. 1. Fig. 2. Fig. 3. CROSS SECTIONS OF INFECTED PINE LEAVES. PLATE XLIII. ^. ■' "^f^ ^^^^Sfe=n -tt/ ^ CROSS SECTIONS OF INFECTED PINE LEAVES. PLATE XLIV. TELIAL STAGE AND ITS GERMINATION. University of Connecticut Libraries 39153029230739 f/