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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 





169.4 


42.4 


211.8 


Twice over Bordeaux 

4 times. (1) 


. . . t 

s 
c 


100 


7-8 


72.0 


18.5 


90.5 





174.2 


44.8 


219.0 


Twice over Bordeaux 

4 times. (2) 


. 1 


100 


34-35 


58.0 


13.0 


71.0 





140.4 


31.4 


171.8 


Check. No Bordeaux 

(2) 


100 


38-39 


52.5 


17.0 


69.6 





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 





158.5 


38.7 


197.2 


(1) 




Once over Bordeaux 4 times 

(1) 


100 


7-8 


56.5 


15.5 


72.0 





136.7 


37.5 


174.2 


Twice over Bordeaux 4 times.. .... 

(1) 


100 


21-22 


53.5 


13.5 


67.0 





129.4 


32.7 


162.1 


Check. No Bordeaux 


100 


3-4 


73.0 


13.5 


86.5 





176.6 


32.7 


209.3 


(2) 




Once over Bordeaux 4 times 

(2) 


100 


8-9 


67.5 


16.5 


84.0 





163.4 


39.9 


203.3 


Twice over Bordeaux 4 times.. . . . . 

(2) 


100 


21-22 


67.5 


10.5 


78.0 





163.4 


25.4 


188.8 


Totals, Check. 


200 


2-3 

3-4 


138.5 


29.5 


168.0 





167.6 


35.7 


203.3 






Totals, Bordeaux once over 


200 


7-8 
8-9 


124.0 


32.0 


156.0 





150.0 


38.7 


188.7 


Totals, Bordeaux twice over 


200 


21-22 

21-22 


121.0 


24.0 


145.0 





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 





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 





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 








16 





















Aug. 27 


9 
































Sept. 6 


57 


3 


5 


32 


'6 










ie 


'3 










Sept. 12 


11 
































Sept. 14 


5 








'5 


'6 






















Sept. 24 


9 








9 















. . 










Oct. 15 


21 


4 


19 


10 


1 






















Oct. 16 


8 


4 


50 


























Oct. 17 


61 


13 


21 


























Nov. 1 


11 








ii 













• • 












Total... 


213 


24 


11 


83 


1 








16 


3 








1918 
























June 13 


1 


1 


100 


, 


















Sept. 30 


12 








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 













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 
































Oct. 30 


3 
























"3 


'6 






Total. . . 


193 


72 


37 


7 





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 


fir 


lOCl 


ilat 


ionj 


th 


ey 


wei 


-e E 


LOt exa 


ctly th 


le 


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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. 






























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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. 




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