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43
Connecticut Agricultural ^"^-^^
Experiment Station
NEW HAVEN, CONN.
Report of the Botanist
For Years 1917-18
G. P. CLINTON, Sc.D.
(Being BuUetin 214, Connecticut Agricultural Experiment
Station)
CONTENTS
Page
Co-operative Potato Spraying in 1917 411
Fertilizer Experiments with Potatoes 421
Inspection of Phaenogamic Herbaria for Rusts on Ribes sps 423
Infection Experiments of Pinus strobus with Cronartium ribicola 428
The Bulletins of this Station are mailed free to citizens of Connecti-
cut who apply for them, and to others as far as the editions permit.
Issued Sept., 1919
CONNECTICUT AGRICULTURAL EXPERIMEOT STATION
OFFICERS AND STAFF.
BOARD OF CONTROL.
His Excellency, Marcus H. Holcomb, ex-offi,cio, President.
James H. Webb, Vice President Hamden
George A. Hopson, Secretary Wallingford
E. H. Jenkins, Director and Treasurer New Haven
Joseph W. Alsop Avon
Charles R. Treat Orange
Elijah Rogers Southington
William H. Hall South Willington
Administration. E. H. Jenkins, Ph.D., Director and Treasurer.
Miss V. E. Cole, Librarian and Stenographer.
Miss L. M. Brautlecht, Bookkeeper and Stenographer.
William Veitch, In charge of Buildings and Grounds.
Chemistry.
Analytical Laboratory. E. Monkoe Bailey, Ph.D., Chemist in charge.
C. B. Mohison, B.S., C. E. Shepakd, (.,.,, ^,
,, ,_, ______ _„ r Assistajit (.hemtsts.
M. d Esopo, PhB., H. D. Edmond, B.S., ' »
Frank Sheldon, Laboratory Assistant.
V. L. Chtirchill, Sampling Agent.
Miss Alta H. Moss, Stenographer.
Protein Research. T. B. Osborne, Ph.D., D.Sc, Chemist in charge.
Miss E. L. Ferrt, M. S., Assistant.
Botany. G. P. Clinton, Sc.D., Botanist.
E. M. Stoddard, B.S., Assistant Botanist.
Florence A. McCoRxncK, Ph.D., Scientific Assistant.
G. E. Graham, General Assistant.
Mrs. W. W. Kelset, Secretary.
Entomology. W. E. Britton, PhD., Entomologist; State Entomologist.
B. H. Walden, B.Agr., Phillip Garm.^n, Ph.D.,
M. P. Zappb, B.S., I. W. Davis, B.Sc, Assistants.
Miss Gladys M. Finlet, Stenographer.
Forestry. W.^^lter O. Fillet, Forester; also State Forester,
and State Forest Fire Warden.
A. E. Moss, M.F., Assistant State and Station Forester.
Miss E. L. Avert, Stenographer.
Plant Breeding. Donald F. Jones, S.D., Plant Breeder.
C. D. HuBBELL, Assistant.
Vegetable Growing. W. C. Pblton, B.S.
CO-OPERATIVE POTATO SPRAYING IN 1917.
G. P. Clinton, Botanist.
L. F. Har"vet, Farm Bureau Agent.
Nature of Experiments.
This is the second report on co-operative potato spraying, the
first having been made by G. P. Clinton and F. E. Rogers, former
County Agent of New Haven County, in the Station's Report
for 1916, pp. 355-64. The experiments for 1917 were confined to
home-made 4-4-50 Bordeaux, this having proven most practical
in the previous experiments, and were merely to determine how
efficient spraying was under ordinary farm conditions, and, as it
turned out, in a year when blight was not especially troublesome.
It was planned to give four to six treatments according to weather
conditions and with the equipment at hand. The conditions
varied so at the different farms where the experiments were con-
ducted that the details are given under each. Thanks are due the
owners for their aid in conducting the experiments, which were
made at the following places: Arthur D. Clark's, Charles R.
Treat's, and S. D. Woodruff & Sons', Orange; S. A. Smith &
Son's, CHntonville; Whittemore's Estate, W. M. Shepardson,
Manager, Middlebury.
Experiments were also planned at the farm of Robert Treat,
Woodmont. Two sprayings were made by Mr. Treat, one about
the 1st of July and the second on July 20th, but further treat-
ments were omitted because of the dying condition of a large part
of the field the last of that month. This unusual trouble may
have been partly due to hce, but probably drought and unbal-
anced fertilization, factors that figured so prominently in the wilt
and prematuring of fields in this State in 1918, were as much to
blame. No yields were taken from this field, as evidently the two
sprayings had not been of value under these conditions.
The first sprayings were made early in July at all the places
before any signs of the blight had appeared. In fact the very
first blight found that year in the State was on July 24th at South
Manchester, and was not found in any of the sprayed fields until
considerably later. Blight caused no very evident harm except in
the Middlebury field, which was quite wet in spots. At the
412 CONNECTICUT EXPERIMENT STATION BULLETIN 214.
Treat farm the vines were all dead from sun scorch before any
signs of blight appeared. Their premature death during August
was due to very hot weather on the last few days of July and the
first of August. The damage caused by this hot weather made
unnecessary the sprayings planned for the last of August, except
at the Whittemore estate.
The results of spraying were determined by yields taken of 100
foot lengths, in comparable rows of the different plots, and the
yields per acj-e figured from these by the method indicated in the
previous report. No figures for cost of labor or supphes were kept,
but those given in the 1916 report apply fairly well. The details
of treatments, observations and results at each place follow.
At Arthur D. Clark's Farm.
Mr. Clark's field of three or four acres was very conveniently
situated to the barn with water supply, etc. The field of Green
Mountains was in fine shape when the spraying was started and
was on high ground, somewhat rolling, with variable soil condi-
tions, especially as regards retention of moisture. A one-horse
Iron Age power sprayer, with single nozzles provided with strainer
attachments for each of four rows, was used. The four sprayings
were made as follows: 1st, July 6th; 2nd, July 16th; 3rd, July
27th; 4th, Aug. 13th. The sprayed plots were gone over twice, in
opposite directions, at each spraying. In the first two treat-
ments arsenate of lead paste, rate of 4 lbs. per 50 gals., was used
in the Bordeaux for potato bugs, and the checks were sprayed at
the same time and rate with the paste in water.
The plots were as follows:
Rows 1 to 4. Check.
Rows 5 to 36. Bordeaux (twice over).
Rov>rs 37 to 40. Check.
Rows 41 on. Sprayed as desired by Mr. Clark.
The first twelve rows were planted with Maine grown seed, and
the remainder with home-grown (one season) of same variety.
On July 27th the vines of the Maine grown seed were distinctly
larger and so more difficult to coat thoroughly with the spray
than the home grown. Also on this date the effect of the poorer
and more leachy soil in certain parts of the field began to show in
the prematuring and yellowing of the vines, despite the fairly
CO-OPERATIVE POTATO SPRAYING. 413
good fertilizer applied. At the time of the fourth spraying, August
13th, some of the vines were dying prematurely, especially on the
poorer part of the field, and more of those from home grown than
from the Maine grown seed. There was no blight present. The
hot weather of the last of July with resultant drought conditions
in the leachier soil was entirely responsible for the trouble. There
was little difference between sprayed apd unsprayed plots. On
Aug. 28th, one fourth of the vines were dead due to drought, with
sprayed plots a little better than unsprayed. Found the first
blight at this time on the low spot in the field but it appeared too
late to cause much damage. Two rows of the Maine grown seed,
from which Mr. Clark had cut six inches off the tops about two
weeks before, were greener than the other vines in the rows on
either side.
The potatoes were dug October 15th. The results of the yields
are given in Table 1. From this it can be seen: 1st, That the
Maine grown seed yielded better than the home grown, as was
indicated by the appearance of the vines earlier; 2nd, That in
each case the sprayed plots yielded better than the corresponding
unsprayed plots; 3rd, That the average increase was about 18
bushels per acre, enough to slightly more than pay the cost of
the spraying at the current price of potatoes per bushel (probably
$15.00 clear profit) ; 4th, That the greatest difference between the
sprayed and unsprayed plots was shown on the wet end of the
field where the blight had been found on the foliage doing some
damage.
At Charles R. Treat's Farm.
Green Mountain potatoes were planted here on two or three
acres of sod land, and had the usual good fertilization and cultiva-
tion given by Mr. Treat. The sprayings were made with a one-
horse 4-row Iron Age power sprayer with single nozzles provided
with strainers. Part of the field was gone over once at each spray-
ing with Bordeaux and part twice, the second time in the opposite
direction. The sprayings were made on the following dates:
1st, July 2nd; 2nd, July 16th; 3rd, July 27th; 4th, Aug. 13th.
In the first two treatments, arsenate of lead at the rate of 4 lbs.
per 50 gals, was used in the Bordeaux, and in water for the checks.
The plot's were as follows :
Rows 1 to 5. Check.
414 CONNECTICUT EXPERIMENT STATION BULLETIN 214.
TABLE 1. DATA FOR THE A. D. CLARK FARM, ORANGE.
Treatment.
Feet
dug
Row
lbs.
1st.
lbs.
2nd.
lbs.
Total.
No.
rot.
Rate
1st.
bu. per
2nd.
acre
Total
Check. No Bordeaux
(1)
i
5
-1
100
2-3
70.0
17.5
87.5
0
169.4
42.4
211.8
Twice over Bordeaux
4 times. (1)
. . . t
s
c
100
7-8
72.0
18.5
90.5
0
174.2
44.8
219.0
Twice over Bordeaux
4 times. (2)
. 1
100
34-35
58.0
13.0
71.0
0
140.4
31.4
171.8
Check. No Bordeaux
(2)
100
38-39
52.5
17.0
69.6
0
127.1
41.1
168.2
Check. No Bordeaux
(1)
. . . . T
(
c
3
100
2-3
84.0
13.0
97.0
25
203.3
31.4
234.7
Twice over Bordeaux
4 times. (1)
<
100
8-9
101.5
12.5
114.0
18
245.6
30.3
275.9
Totals, Check
300
2-3
38-39
2-3
206.5
47.6
254.0
25
166.6
38.3
204.9
Totals, Bordeaux
300
7-8
34-35
8-9
231.6
44.0
275.5
18
186.7
36.6
222.2
(1) Maine grown seed. (2) Home grown seed.
Rows 6 to 20. Bordeaux, once over each treatment.
Rows 21 to 81. Bordeaux, twice over each treatment.
The field was low, quite level and fairly uniform in character.
On July 27th the vines were in fine shape except a small spot in
the twice over Bordeaux plot, where lice had caused some injury.
On Aug. 13th, however, they showed one-half the foliage dead,
so the treatment on this date did little good. By Aug. 28th they
were four-fifths dead. No difference showed in favor of the
sprayed plots, and no bhght was found at any tune in the field.
There is no doubt that the vines were so severely injured by the
three or four days of unusually hot weather the last of Jul}'' and
Aug. 1st, resulting in premature death during August, that the
spraying had not yet begun to produce the beneficial effects that
usually appear from the last of August on. The vines here suf-
fered more from this hot spell than at any of the other farms.
One row next the corn, which shaded it somewhat, kept green
longer than the others.
CO-OPERATIVE POTATO SPRAYING. 415
TABLE 2. DATA FROM THE C. R. TREAT FARM, ORANGE.
Treatment.
Feet
dug
Row
lbs.
1st.
lbs.
2nd.
lbs.
Total.
No.
rot.
Rate
1st.
bu. per
2nd.
acre
Total
Check. No Bordeaux
100
2-3
65.5
16.0
81.5
0
158.5
38.7
197.2
(1)
Once over Bordeaux 4 times
(1)
100
7-8
56.5
15.5
72.0
0
136.7
37.5
174.2
Twice over Bordeaux 4 times.. ....
(1)
100
21-22
53.5
13.5
67.0
0
129.4
32.7
162.1
Check. No Bordeaux
100
3-4
73.0
13.5
86.5
0
176.6
32.7
209.3
(2)
Once over Bordeaux 4 times
(2)
100
8-9
67.5
16.5
84.0
0
163.4
39.9
203.3
Twice over Bordeaux 4 times.. . . . .
(2)
100
21-22
67.5
10.5
78.0
0
163.4
25.4
188.8
Totals, Check.
200
2-3
3-4
138.5
29.5
168.0
0
167.6
35.7
203.3
Totals, Bordeaux once over
200
7-8
8-9
124.0
32.0
156.0
0
150.0
38.7
188.7
Totals, Bordeaux twice over
200
21-22
21-22
121.0
24.0
145.0
0
146.4
29.0
175.4
(1) West side, south end of rows. (2) West side, center of rows.
The potatoes were dug on Sept. 27th. The results of the yields
are given in Table 2. From the results and the observations made,
it is evident: 1st, That the spraying did no good; 2nd, This was
due to the premature death of the vines resulting from the sudden
hot spell in July and August, before any bhght got started; 3rd,
The trampling of the ground and vines in spraying resulted in a
decreased yield, shown most markedly in the twice over Bordeaux
plots. Ordinarily where the vines are not Idlled prematurely,
this sHght injury due to trampling is overcome later in the season
and additional gain made through the greater vigor and lon-
gevity of the sprayed vines.
At S. D. Woodruff & Sons' Farm.
As at the other places the potatoes were Green Mountains, with
the fertilization and cultivation as ordinarily given by the owner.
The field was similar to that at the Clark farm, being somewhat
416 CONNECTICUT EXPERIMENT STATION BULLETIN 214.
lower and perhaps less variable in soil conditions, though none
the less rolling. The planting, made with a planter, showed quite
a few misses giving an uneven stand in the rows in scattered
places. The one-horse Iron Age power sprayer used here, while
of the four-rowed type with a single nozzle to a row, had a some-
what stronger pump, that gave a more even distribution of spray
material. The sprayings were made on the following dates:
1st, July 6th; 2nd, July 16th; 3rd, July 27th. The fourth spraying
planned for Aug. 13th was omitted because the machine was not
available. Poison for bugs was used in same way as at the other
farms.
The plots were as follows :
Rows 1 to 16. Check.
Rows 17 to 56. Bordeaux, twice over each time in opposite
directions.
Rows 57 to 60. Check.
Row 61 on. Sprayed as desired by owner.
On August 13th the field was somewhat weedy, and by Aug.
28th, the weeds were so large and abundant as to cause more or
less damage. On neither of those dates did the vines show as
much injury from the hot weather of July as did those at either
the Clark or the Treat farm. This was probabl}'" due to better soil
conditions for retaining moisture. Blight had not appeared in
the field up to the last of August. Little difference was seen
between the sprayed and unsprayed parts of the field.
The potatoes were dug on Sept. 25th. The results are shown
in Table 3. The conclusions are as follows: 1st, That the spraj^ed
plots gave a very slight increase over the unsprayed; 2nd, That
there was more variability in yield between the two checks than
there was between them and the Bordeaux plots, probablj^ due to
uneveness of stand and soil conditions, though we tried to avoid
such in selecting the spots that were dug; 3rd, The few sprayings
given, the weediness of the field, the absence of bhght, etc., made
conditions such that very favorable results from the spraying could
not be expected.
At S. A. Smith & Son's Farm.
The Green Mountain potatoes at this place were sprayed the
first time with a hand-power barrel pump placed on a wagon to
which was attached a stationary nozzle arrangement for spray-
CO-OPERATIVE POTATO SPRAYING.
417
TABLE 3. DATA FROM THE
S. E
. WOODRUFF & sons'
FARM, ORANGE.
Treatment.
Feet
dug
Row
lbs.
1st.
lbs.-
2nd.
lbs.
Total.
No.
rot.
Rate
1st.
bu. per
2nd.
acre
Total
Check. No Bordeaux
(1)
100
14
81.5
15.5
97.0
8
197.2
37.5
234.7
Twice over Bordeaux 3 times
(1)
100
19
72.0
15.5
87.5
0
174.2
37.5
211.7
Check. No Bordeaux
100
58-59
64.0
9.5
73.5
6
154.9
23.0
177.9
(2)
Twice over Bordeaux 3 times
(2)
100
51,55
75.0
13.0
88.0
5
181.5
31.5
213.0
Totals, Check
200
14
58-59
145.5
25.0
170.5
14
176.1
30.3
206.4
Totals, Bordeaux
200
19
51,55
147.0
28.5
175.6
5
177.9
34.5
212.4
(1) Rows next road. (2) Rows center of field.
ing four rows, each from a single nozzle. This worked so poorly
that part of the rows were gone over three times to thoroughly
coat them. The next two sprayings were made by hand with two
lines of hose and were done more thoroughly than at any other
place. The first two sprayings contained powdered lead arsenate
at rate of 2 lbs. per 50 gals. Bordeaux, for the bugs, and the
checks received similar amounts in water. The sprayings were
made on following dates: 1st, July 6th; 2nd, July 17th; 3rd, Aug.
6th. The abundance of weeds made it undesirable to give the
fourth spraying.
The plots were as follows:
Rows 1 to 4. Check.
Rows 5 to 48. Bordeaux, thorough hand treatments.
Rows 49 to 55. Check.
On August 6th the field was becoming very weedy, and on Aug.
30th the weeds were so large and numerous as to seriously inter-
fere with the crop, except in six rows where they had been pulled
on Aug. 6th. The vines suffered little from the July hot spell
and on Aug. 30th were greener than at any of the Orange farms.
The first check rows showed little blight on Aug. 30th; how-
ever, the second check rows, in a lower damper part of the field,
showed more. The spray at this time had mostly washed off the
vines.
418 CONNECTICUT EXPERIMENT STATION BULLETIN 214.
TABLE 4. DATA FROM S. A, SMITH
& son's farm,
CLINTON VILLE.
Treatment
Feet
dug
Row
lbs.
1st.
lbs.
2nd.
lbs.
Total
No.
rot
Rate
1st.
bu. per
2nd.
acre
Total
Check. No Bordeaux
100
2-3
64.5
13.5
78.0
5
156.1
32.7
188.8
(1)
Twice over Bordeaux 3 times
(1)
100
5-6
81.0
15.5
96.5
3
196.0
37.5
233.0
Twice over Bordeaux 3 times
(2)
100
43-44
48.5
15.5
64.0
0
117.4
37.5
154.9
Check. No Bordeaux
(2)
100
50-51
53.0
22.0
75.0
2
128.3
53.2
181.5
Totals, Check
200
2-3
50-51
117.5
35.5
153.0
7
142.2
42.9
185.1
Totals, Bordeaux
200
5-6
43-44
129.5
31.0
160.5
3
156.7
37.5
194.2
(1) Weeded. (2) Not weeded.
The potatoes were dug October 8tli. The results are given in
Table 4. From this experiment it is seen: 1st, That the sprayed
vines gave a little better yield than the unsprayed, about enough
to pay for the cost of the treatments; 2nd, That the part of the
field kept thoroughly weeded showed greater difference in favor
of the spraying and also in favor of weedmg. We do not know why
Bordeaux plot 2 gave a smaller yield than check plot 2, unless the
former was from home grown and the latter from Maine grown
seed which was used in this end of the field.
At Whittemore's Estate Farm, Middlehury.
This field of several acres of Green Mountains was on a hill side
and part of one end was quite moist even in dry weather, so that
in the early season the potatoes were nearly smothered out there.
It had been in sod the previous year, top dressed in the spring,
and when plowed under had been so very liberally fertilized that
the soil was in unusually good condition. The vines were sprayed
with the large two-horse, 4-row Iron Age power sprayer that had
three nozzles to a row, one above and on either side. The power
was sufficient to give a very misty spray that with slow driving
coated the vines in fair shape with the one spraying that was
given at each treatment. Arsenate of lead was used in the first
two treatments and on the check for bugs. The spraj^ings were
CO-OPERATIVE POTATO SPRAYING.
419
made on the following dates: 1st, July 3rd; 2nd, July 11th; 3rd,
July 19th; 4th, July 30th; 5th, Aug. 14th; 6th, Aug. 27th; 7th,
Sept. 3rd.
The plots were as follows :
Rows 1 to 12. Bordeaux, once over.
Rows 13 to 16. Check.
Rows 17 on. Bordeaux, once over.
The hot weather did not hurt this field and it remained green
much longer than any of the others. In fact at the time of digging,
Oct. 16th, some of the vines were still green! One of the largest
hills, the vine of which was unusually luxuriant, yielded seven
large potatoes and two small ones, a total weight of five and a half
pounds. The tubers on the whole were rather large, one of the
largest weighing eighteen and a half ounces. The large yield and
large size of tubers were due to the good fertilization and the
extended growth period of vines resulting from the spraying.
Blight eventually appeared in September and caused death of
the foHage and rot of the tubers especially in the wet area, and to a
less extent in the unsprayed drier part of the field.
The yields are shown in Table 5. An examination of this shows:
1st, That the spraying very considerably increased the yield in
TABLE 5.
DATA FROM THE WHITTEMORE ESTATE FARM, W.
SON, MANAGER.
M. SHEPARD-
Treatment.
Feet
dug
Row
lbs.
1st.
lbs.
2nd.
lbs.
Total.
No.
rot.
Rate
1st.
bu. per
2nd.
acre
Total
Once over Bordeaux 7 times. .. .
100
10-11
124.6
11.5
136.0
3
301.3
27.8
329.1
Check. No Bordeaux
100
14-15
95.5
7.5
103.0
60
231.1
18.2
249.3
Once over Bordeaux 7 times
100
18-19
143.5
8.0
151.5
11
347.2
19.4
366.6
Once over Bordeaux 7 times.. . .
(1)
100
10-11
85.5
8.0
93.5
106
206.9
19.4
226.3
Check. No Bordeaux
100
14-15
22.5
6.0
28.5
257
54.5
14.5
69.0
(1)
Once over Bordeaux 7 times.. . .
(1)
100
18-19
34.0
6.0
40.0
253
82.3
14.5
96.8
Totals, Check
200
14-15
14-15
118.0
13.5
131.5
317
142.8
16.3
159.1
Totals, Bordeaux
400
(2) 10-11
(2) 18-19
387.5
33.5
421.0
373
234.4
20.3
254.7
(1) Unusually wet spot covering only small part of the field.
420 CONNECTICUT EXPERIMENT STATION BULLETIN 214.
each case over the adjacent unsprayed rows; 2nd, This increase
averaged 95 bushels per acre; 3rd, The increased yield was in
part due to the prolonged life of the vines, and in part to pre-
venting rot of the tubers; 4th, The spraying did not prevent rot
in the very wet part of the field, where considerably over half of
the tubers rotted though it helped somewhat even there.
General Conclusions.
These were potato spraying experiments, chiefly with horse-
power sprayers, carried on under the ordinary operations at five
different farms. The hot weather, of three days the last of July
and the 1st of August, seriousl3^ interfered with the results by
prematurely killing or injuring the vines in August in two of the
fields, and to a small extent in two more. This rendered unneces-
sary the last one or two sprayings that had been planned. Blight
caused no conspicuous injury except in one field. The spraying
harmed rather than helped in one field, due to tramphng of vines
in spraying and the premature death of the vines from drought
before the effect of spraying showed; two fields were benefitted
about enough to pay for the cost of spraying; one field gave an
increase about (18 bushels) slightly above the cost; one field, where
blight was prevented, gave an increase (95 bushels) very greatly
in excess of the cost of spraying.
FERTILIZER EXPERIMENTS WITH POTATOES.
E. H. Jenkins, Director.
G. P. Clinton, Botanist.
The following is an account of observations on the yields of
potatoes as affected by different fertilizers, especially as regards
potash, conducted by Mr. W. M. Shepardson, Middlebury,
Conn., the writers making the weighings at digging time, and by
Mr. F. C. Davis, of Somers.
The first lot, northwest of Mr. Bristol's house, was in turf
the previous spring and had not been cultivated for many years.
In 1917 it was plowed, dressed with 25 loads of manure to the acre,
and the fertilizers named were put in the drill at the rate of 1000
pounds per acre. The rows were 2^^ feet apart. The Green
Mountain potatoes were planted by machine on June 9th. The
stand obtained was quite uniform.
The potatoes were dug on Oct. 19th, and the crop on the two
central rows of each plot, 100 feet long, was weighed and sorted
into firsts and seconds. Thefee tubers were obviously scabby
where ashes were used, and more scabby where 2000 pounds of
ashes were used than where half that amount was apphed.
The weights in lbs. of the potatoes on the 2 rows were as follows :
lbs. lbs. lbs. *Est. Total
Fertilizers. Firsts. Seconds. Total. Bu. per acre
Essex 4-8-4 (1916 stock) 112% 40 1523^ 184 . 5
" 4-10-0 122% 37% 160 193.6
" 4-10-0, 1000 lbs. ashes per acre 132% 37% 170 205.7
« 4-10-0,2000 " " " " 157% 22% 180 217.8
Buffalo 2-9-4 (Templeton) 117% 30 147% 178.5
Essex 4-8-4 (1916) 127% 35 162% 196.6
Bowker 3%-9-4 (1916) 122% 42% 165 199.7
Buffalo 2-9-4 (Templeton) 117% 35 152% 184.5
Buffalo 2-9-4 (Outside rows) 125 27% 152% 184.5
*Estimated on basis of an acre field 16 by 10 rods, rows running length-
wise of field, and 3 feet apart.
The most noticeable things are that the duplicates with Essex
and Buffalo in different parts of field gave rather uniform results
indicating uniformity in the soil of the field.
The addition of ashes to the Essex 4-10-0 increased the yield and
2000 lbs. increased it more than 1000 lbs., particularly in the No.
422 CONNECTICUT EXPERIMENT STATION BULLETIN 214.
1 potatoes. The ashes however induced scab, though not enough
to seriously damage market quahty.
On a neighboring field planted to Green Mountain on June 8th
in rows 2 ft. 10 in. apart, 2 rows each 150 feet long were dug in each
plot. 1000 lbs. of the fertilizers were used and on some plots
varying amounts of wood ashes were added.
*Est. of
Firsts. Seconds. Totals. Total bu. per
lbs. lbs. lbs. acre.
Essex 4-8-4 180 75 255 205.7
" 4-10-0, no ashes, 200 55 255 205.7
" " " « 1000 lbs. ash 165 70 235 189.6
« " " « 2000" " 230 80 310 250.1
" " " « 3000" " 250 60 310 250.1
*Estimated. on basis of an acre field 16 by 10 rods, rows running length-
wise of field, and 3 feet apart.
Here 1000 lbs. ashes had no apparent effect, 2000 and 3000 lbs.
ashes increased yield to same amount. Scab was more abundant
where ashes were used than on plots where not used, but there
was not much difference due to the different amounts used.
In neither field did the Essex 4-8-4, with potash, give a better
yield than the 4-10-0 without it. However, in both fields the ad-
dition of a ton or more of wood ashes to the Essex 4-10-0 materially
increased the jdeld, due either to the greater amount of potash or
to the lime they contained.
Mr. F. C. Davis, of Somers, reports in 1918 more favorable
returns from potash, where he used it alternating on seven strips
of twelve rows each, in a 3-8-3 formula in comparison with a
4-10-0. The land was a gravelly loam in corn the previous year.
The fertilizers were apphed in three doses as follows: 800 lbs.
before the first harrowing, working it in thoroughly with the
stalks and plowing under, 400 in the planter and 600 at the time of
the second cultivation.
There was no difference between the strips during the growing
season until the last ten days, the potash strips remaining ahve
that much longer. The difference in yield was about 50 bushels
per acre in favor of the potash fertilizer. This at the price the
potatoes were sold was a gain of $75 per acre or, deducting the
extra cost of this fertilizer, a net gain of
INSPECTION OF PHAENOGAMIC HERBARIA FOR RUSTS
ON RIBES SPS.
G. P. Clinton, Botanist.
Not infrequently one can find specimens of certain fungi easier
by looking through a collection of flowering plants in an herbarium
than by going out doors and looking for them on the hving hosts.
This is true of certain smuts and rusts and especiWlly so if the de-
sired hosts do not occur in one's vicinity but are found in a large
phaenogamic herbarium near by. Thinking that such a search
through a number of herbaria perhaps might throw light on the
early occurrence of Cronartium ribicola in this country, the writer
in 1916 and 1917 carefully looked over the specimens of Rihes,
including Grossularia, in the following eastern herbaria: (1) Conn.
Agr. Sta. Herb., (2) Conn. Bot. Club Herb., (3) Yale Univ. Herb.,
(4) N. Y. Bot Card. Herb., (5) Columbia Univ. Herb., (6) Grey
Herb., (7) N. E. Bot. Club. Herb., (8) U. S. Nat. Herb. Re-
quests were also sent to several central and western herbaria that
leaves containing suspicious rust specimens be sent the writer
and several such were received from the following: (9) Mo. Bot.
Gard. Herb., sent by Greenman, (10) Univ. of Wash. Herb., by
Hotson, (11) Univ of Calif. Herb., by Jepson. No rusts, however,
v/ere foimd on specimens sent from the last two herbaria.
While this investigation did not throw any light on the occurence
of Cronartium ribicola in this country, except what might be
considered negative evidence, still information was obtained of its
existence elsewhere and of the distribution, hosts, etc., of three
other rusts in this country. We have thought it worth while to
record here this data, together with some general remarks on the
same. The figures in parentheses, following the name of the col-
lector with each collection, refer to the herbarium, as numbered
in the preceding paragraph, in which the Rihes were examined.
Most of these fragmentary specimens containing the enumerated
rusts are now in the herbarium of the Conn. Agr, Exp. Station.
Besides these rusts several other fungi were observed but no
particular attention was paid to them. They included the fol-
lowing: Gleosporium Rihis (Lib.) Mont. & Desm., on Rihes Lobbii,
KHckitat Co., Wash., 7 Au. 1897, Suksdorf (6); on Rihes nigrum,
Mt. Lancaster, Coos Co., N. H., 25 Au. 1913, Pease (7). Septoria
424 CONNECTICUT EXPERIMENT STATION BULLETIN 214.
aurea destruens E & E., on Rihes aureum, Mobridge, S. Dak., 28
Jl. 1907, Bailey (8).
Aecidium Grossulariae (P.) Schum.
This fungus has now been proven by infection experiments to
be the I stage of Puccinia Grossulariae (Schum.) Lag. with its II
and III stages on Car ex sps. Whether or not all of the aecia on
the various species of Rihes scattered over the country are the
same thing can only be determined by further inoculation tests.
Arthur (Journ. Myc. 8:53. 1902.) has described another Puc-
cinia, P. albiperidia, with its II and III stages on Carex and its I
stage on Ribes sps., distinguished by its white or nearly white
aecia {Aecidium alhiperidium) . The same author (Mycologia
4: 14. 1912.) thinks that Uromyces uniporulus Kern also has its
aecia on Rihes. We have however grouped all the specimens
reported here under Aecidium Grossulariae as they showed no
evident difference. This rust occurs very commonly on herbarium
material and in the immature stage resembles somewhat the II
stage of Cronartium rihicola. However, one soon learns to distin-
guish it in this stage with the hand lens through the larger size of
the aecia and the presence of pycnia. This rust was collected on
eleven different hosts as follows :
On Rihes americanum (R. floridum) : — ^New Haven, Ct., 27 My.
1879, Livingston (3); Oxford, Ct., 23 Je. 1901, Harger (2);
Bellevue, Wise, 27 My. 1882, Schnelle (6); Norway, Neb.,
22 Je. 1893, Rydberg (6, 8).
On Rihes hracteosum: — Chilliwach Valley, B. C, 8 Jl. 1901,
Macoun (8).
On Rihes (Grossularia) Cynoshati: — Jackson, N. H., 29 Jl. 1876,
Allen (1); Orono, Me., 25 Au. 1913, Pease (7); Northumberland,
N. H., 31 Jl. 1909, Pease (7); Manchester, Vt., 30 Je. 1898, Day
(7); Colebrook, N. H., 13 Jl. 1907, Pease (7); Kingston, Ont., 5
Je. 1902, Fowler (8); New Harpersfield, N. Y., 8 Je. 1906, Toppin
(8).
On Rihes (Grossularia) divaricatum: — Yellowstone, Neb., Au.
1854, Hayden (9); Chehalis Co., Wash., 10 My. 1897, (4).
On Rihes (Grossularia) gracile: — Near Minneapolis, Minn., My.
1891, Alton (3).
On Rihes (Grossularia) hirtellum: — Berhn, Mass., 13 Je. 1915,
Winslow (7); Clinton Co., la., 23 Ap. 1878, Butler (1); Foxcroft,
RUSTS ON RIBES IN HERBARIA. 425
Me., 25 Je.,1894, Fernald (7); Dead River, Me., 19 Au. 1896,
Fernald & Strong (7).
On Rihes lacustre: — Sherburne, Vt., 18 Je. 1899, (4); Pittsburg,
N. H., 5 Jl. 1907, Pease (7).
On Rihes prostratum:—Mt. Washington, N. H., 24 Je. 1893,
Greenman (9), 24 Je. 1898, Williams (7); Straits Belle Isle, Lab.,
1 Au. 1910, Fernald & Wiegand (6);Orono, Me., 1 Jl. 1892,
Fernald (7); Cumberland, Me., 29 My. 1902, Chamberlain (7);
Mt. Mansfield, Vt. 2 Jl. 1897, Wilhams (7); Oakham, Mass.,
12 My. 1912, Fernald (7); Adams, Mass., 4 Je. 1898, Churchill (7).
On Rihes (Grossularia) rotundifolium: — Ames, la., Hitchcock
(9); la., 1871, (9); CKnton Co., la., 22 Ap. 1878, Butler (1).
On Rihes {Grossularia) saximontanum: — Platte Canyon, Natrona
Co., Wy., 7 Je. 1901, Godding (9).
On Rihes {Grossularia) setosum: — ^Buffalo, Wy.,Jl. 1900, Tweedy
(3) ; Bozeman, Mont., 18 My. 1901, Jones (8).
Coleosporium rihicola (C. & E.) Arth.
This is a western rust of which the aecial stage apparently is not
yet known. It is probably some Peridermium on the leaves of
Pinus sps. The uredinial stage was first described in 1878
(Grev. 6: 86.) by Cooke & Ellis from the Rocky Mts., on Rihes sp.
Arthur (N. A. Flora 7: 86. 1907) who placed it under the genus
Coleosporium and described the telial stage, gives Rocky Mountains
{Colorado) and Rihes {leptanthuin) as the type locality and host.
In 1885 Peck (Bull. Torr. Bot. Club 12 : 36.) again described this
species on Rihes from New Mexico under the name Uredo Jonesii.
It is interesting to note here that at least 24 years before Cooke &
Ellis first described the fungus it was unknowingly collected by
Bigelow (Botanist, Whipple Exp. R. R. Route Miss. R. to Pacific
Ocean, Fort Smith to the Rio Grande in 1853-i) on Ribes leptan-
thum as shown by specimens taken from this host in the Gray
Herbarium. Arthur in his monograph cites as hosts five species
of Rihes from eight states. We list here at least eight hosts from
ten different localities, as follows:
On Rihes aureum: — Nogal Canyon, White Mts., New Mex.,
17 Au. 1901, Wooton (II, 4), (III, 8).
On Rihes {Grossularia) hirtellum: — Black Tail Deer Creek,
Yellowstone Park, III, Au. 1884, Tweedy (3).
426 CONNECTICUT EXPERIMENT STATION BULLETIN 214.
On Ribes lacustre (R. echinatum) : — Cascade Mts., Wash., II,
10 Au. 1893, Allen (4).
On Ribes {Grossularia) leptanthum: — Fort Smith to the Rio
Grande, Whipple Exp., Ill, 1 853-4, Bigelow (6).
On Ribes montigenum: — Sandia Mts., Sandoval Co., New Mex.,
Ill, 3 Au. 1910, Wooton (8); Sandia Mts., Balsam Park, New
Mex., II, 17 Ap. 1914, Miss Ellis (4).
On Ribes {Grossularia) pinetorum: — Chloride, New Mex., Ill,
12 O. 1909, Goldman (8).
On Ribes triste (R. rubrum) : — Yakon Valley, 40 Mile River, II,
17 Je. 1902, CoHier (8).
On Ribes TFoZ/w:— Sandia Mts., Balsam Park, New Mex., Ill,
28 My. 1914, Miss Ellis (4).
On Ribes {Grossularia) sp.: — Calif., Ill, 11 S. 1909, Rusby (4).
Cronartiuni ribicola F. deW.
The search through various herbaria for this fungus was to
learn, if possible, whether it occurred in the New England states
earher than the first reported collections made in 1914, and
whether it was native in Colorado on Ribes longiflorum as indicated
by the collections of Bethel. Nothing was learned along either of
these lines. The western Cronartiwn in its II stage was first col-
lected on Ribes longiflorum by Bartholomew in Stockton, Kans.,
Aug. 22, 1892, but has never appeared there since. During the last
ten years Bethel has collected it a number of times on the same
host, in both stages, at Boulder, Denver, and also other places in
Colorado where it appears to be native. Recent experiments by
government investigators have shown these collections to be
distinct from our eastern introduced species altho Ribes longiflorum
is considered by some as a synonym of Ribes odoratum, a common
host in New England for Cronartiwn ribicola. In our search of
herbaria, however, we did not find any Cronartium on Ribes
longiflorum, though we did secure Cronartium ribicola on three speci-
mens, two from Europe and one from Asia, as follows :
On Ribes aureum {R. leiobotrys) : — Cult, plants in Berlin, Ger-
many, II, III, 5 My. 1893, Koehne (6).
On Ribes {Grossularia) divaricatum {R. irrigum) : — Cult, plants in
Berlin, Germany, 9 Au. 1895, Koehne (6).
On Ribes sp:— C. China, W. Hupeh, My. 1900, Wilson, no. 515,
(4).
EUSTS ON RIBES IN HERBARIA. 427
Puccinia Rihis D. C.
This fungus is found in Europe and America, but is apparently
not very common here, at least the writer has never • collected it
in the field. It seems to have a northern distribution and has
been reported from New York by Peck, Wisconsin by Davis,
Minnesota by HoUway, and probably from other states, and was
found on several hosts, but not on the variety reported here.
Peck describes it as a new species, Puccinia pulchella in 1873.
There is only the tehal stage in this rust.
On Rihes triste var. alhinervium: — VanBuren, Me., 24 Jl. 1893,
Fernald (7).
INFECTION EXPERIMENTS OF PINUS STROBUS WITH
CRONARTIUM RIBICOLA.*
G. P. Clinton, Botanist.
Florence A. McCormick, Scientific Assistant.
HISTORICAL CONSIDERATION.
Introduction of Blister Rust in Connecticut, etc. In an article
dealing with heteroeceous rusts found in Connecticut, published
by the Station Botanist (1 p. 394) in his Report for 1907, the state-
ment was made that the blister rust was ''liable to be introduced on
white pine imported from Europe". In April, 1909, Mr. F. A.
Metzger, a forester employed by Mr. C. F. Street at Wilton to set
out a plantation of 10,000 three year old white pine seedhngs
imported through the State Forester from Germany, found fifty to
*In order that the reader may gain at the start a fair idea of the fungus
discussed here, a brief outline of its life-history follows: White Pine
Blister Rust is the common name for the first or I stage of a rust im-
ported accidentally into America on seedling white pines from Europe.
The rust enters the pines through the pores, or stomata, of the needles
in the fall. Usually within a year or two after infection, during late
summer and fall, lemon-yellow drops containing minute spore-like
bodies called pycniospores, ooze out from yellowish (but eventually
brownish) areas on the bark, forming the O or pycnial stage of the fun-
gus. The use of these so-called spores has never been determined.
The next spring (the last of April to the middle of June) after the ap-
pearance of the pycnia, the first true spore stage, called the I or aecial
stage, appears. This forms small, white, fragile, irregular eruptions
on the bark projecting for about a quarter of an inch. They soon break
open at the top disclosing an orange-yellow dusty mass of spores, the
aecial spores.
The aecial spores are blown by the wind, or possibly carried by in-
sects to the leaves of the alternate hosts, which compiise the various
currants and gooseberries belonging to the genus Ribes. Germinating
under favorable conditions of moisture, these spores send their germ
tubes through the stomata, chiefly situated on the under side of the
leaves, and usually within 7 to 12 days give rise there to the II stage
of the fungus, called the uredinial stage. This shows as small roundish
pustules, smaller than the head of a pin, that contain thi yellow semi-
dusty urediniospores. These are washed over the leaf or carried to the
leaves of same or other plants and, on germinating and gaining entrance
to the tissues, produce similar pustules. Through the summer several
generations of these urediniospores may be produced spreading the dis-
* INFECTION OF PINE WITH BLISTER RUST. 429
one hundred infected with an unknown disease. He brought
these to the Station and the trouble was later identified by the
botanist (2 p. 731), who was then absent in Japan, as the white pine
bhster rust. This was the first definite finding of the bhster rust
in this state and one of the first in America, as about the same time
it was also found on imported seedlings set out in several other
New England states and New York. It is quite probable that the
disease was brought into Connecticut at an even earlier date, as
several plantations from foreign stock had been started in 1907,
while nurserymen and others, on whose premises the disease has
since been found in two cases, had imported seedHngs and trees
much earlier. There is also considerable evidence to show that it
was brought into some of the other states some years before it
was definitely first found in 1909. In New York it was introduced
at least before 1906.
ease more or less widely by this repetition. The black currant is
especially susceptible to attack.
From midsummer on, the III or telial stage develops on the Ribes
leaves often appearing in the same pustules following the II stage.
■ This last stage shows as minute reddish-brown hairs about 1 or 2 mm.
long and more or less thickly covering the under surface of the leaves.
These hairs aie composed of leliospoies adhering permanently together.
They germinate immediately under favorable moisture conditions
and give rise to germ threads bearing very small secondary spores,
spotidia, that are blown by the wind to the pine needles, and there gain
entrance as already indicated.
Infected seedlings before the I stage appears in the spring are usually
detected by their bunched leaves and soft swollen stems. When the
fruiting pustules appear they are quite conspicuous and the disease is
easily recognized. After these disappear in late June, there remains
only the roughened dead bark or a yellowish-green area of invaded
smooth bark which will break out the next year, to indicate infection.
Once the cambium is killed all around the stem the parts above die.
Very young infected seedlings do well to live a year, but those two or
three years old may live for several years. On older trees if the infec-
tion is at the ends of the twigs the damage is not serious, but once
the main trunk becomes invaded the tree is doomed though it may re-
main in vigorous growth for several years and seem perfectly healthy
on casual examination of the foliage.
Elimination of Ribes in the vicinity of seed beds, thorough spraying of
the beds with Bordeaux after midsummer if grown in an infected region,
use of uninfected seedlings only for planting, inspection of plantations
from foreign stock for infected pines, destruction of all wild or cultivated
Ribes in plantations and for 300 yards around the same, are precaution-
ary measures advocated for this state.
430 CONNECTICUT EXPERIMENT STATION BULLETIN 214.
Upon positive identification, the botanical and forestry depart-
ments, in co-operation with the U. S. Department of Agriculture,
inspected during 1909 most of the larger plantations scattered over
the state, with the result that the blister rust was found in small
amounts in several of them. All of the infected trees foimd were
destroyed. In 1910 most of these plantations were re-inspected
and several smaller ones were inspected for the first time. About
645,000 out of the 740,000 imported trees that had been set out,
were thus inspected once or twice during the two years. As no
trees were found infected in 1910, the inspection was practically
discontinued. An account of this work appears in the botanist's
report for 1909-10.
In the spring of 1912, Mr. Walden, inspecting an importation
of white pine from Holland at one of the local nurseries, found some
of the seedHngs badly infected, and upon identification as this
rust by the botanist (3 p. 347) Dr. Britton ordered them all
destroyed. Since that year importation of white pines from coun-
tries where the disease occurs has been prohibited by a quarantine
of the U. S. Department of Agriculture.
The first outbreak found in this State on Rihes species, the
alternative host for the II and III stages of this fungus, was
found by the senior writer (3 p. 348) on a few black currants at the
home of Mr. H. B. Birdsey at East Meriden, Conn., in October of
1912. The origin of this infection has never been determined,
since infected pines have not been found in this general region,
though the rust has usually appeared each year since on these
bushes.
Nature of Recent Work. In 1916 the rust having become promi-
nent in certain plantations in northeastern United States and Cana-
da, and especially wide-spread on the Rihes, the U. S. Depart-
ment of Agriculture, and the several interested states, undertook
anew methods looking for its control within the infected areas,
and quarantine laws have since been passed regulating the ship-
ment of five-needle pines and black currants from these to other
parts of the country in order to prevent its introduction into other
states. This necessitated further work in Connecticut. The
forestry department of this station in co-operation with the United
States Department of Agriculture, undertook especially the practi-
cal work deahng with inspection and control. The botanical
department, while also helping with this phase, took as its special
INFECTION OF PINE WITH BLISTER RUST. 431
problem the scientific study of the rust in its various aspects.
The work under the direction of the forester has been carried on
by funds from the U. S. Department of Agriculture and state
appropriations, while that by the botanical department from state
appropriations alone. It is the purpose of the latter department
eventually to publish an illustrated bulletin covering all its in-
vestigations. * The report here deals solely with certain interesting
discoveries that have been made relating to the method of infec-
tion and early development of the bhster rust in the white pine.
It can now be definitely stated that infection takes place through
the stomata on the needles rather than through the stems or buds
as commonly supposed. A preliminary note of this work has
already been published by the writers (4 p. 15) in the Report of the
Blister Rust Committee for 1918.
Previous Investigations. While Dietrick (6 p. 287) as early as
1856 reported both the Peridermium on white pine and the Cro-
nartium on Ribes species from Russia, he evidently did not recog-
nize that they had any relationship to each other. Klebahn
(8 p. XL VIII) in 1888 was the first to prove this relation by
inoculations, using the aecial spores from the white pine on the
leaves of Ribes nigrum. Later he and other European investiga-
tors, and Spaulding (19 p. 244) in America, abundantly verified
this relation by the inoculation of a great number of Ribes species
in similar manner.
When we turn to the inoculation of the white pine with the telial
stage from the Ribes, however, thus completing the evidence of
their relationship, we do not find that many investigators have
reported experimental evidence. In faci:, Klebahn (10 p. 86)
in 1905 seems to have been the first and only European investiga-
tor to report such successful inoculations (made in 1903). As
early as 1890 he (9 p. 62) had attempted inoculations but was
doubtful as to the results, as the plants used may have already
been infected. While there is no doubt that he did infect two
white pines under bell jars in the fall of 1903 (10), by placing in-
fected leaves of Ribes nigrum on a wire net over them, unfortunately
*This report will be published by the writers and Mr. E. M. Stoddard
of this department, who has also co-operated largely with the forestry
department in its control work. The wiiters are indebted to him for
the photographs and photomicrographs with which this article is
illustrated.
432 CONNECTICUT EXPERIMENT STATION BULLETIN 214.
he left the pines out doors over winter and did not carefully
examine them until the middle of the following June.
It was evidently then too late to determine the very first signs of
infection and the manner in which it took place. He noted the
yellow spots on the previous year's leaves, of which we shall speak
in connection with our own experiments, and found the myceHum
of the rust in these spots. He also found that two of the yoimg
stems were of a paler color, distorted, and bore at first juvenile
leaves instead of the normal fascicles of five leaves. In July
spermagonial drops began to appear on the infected branches.
Concerning the manner and place of infection he seemed in
doubt, but makes the following remarks: " The fact that localized
yellow spots were present in these needles does not necessarily
mean that the mycelium arising through infection in the needle
has in especially high degree the power to grow forth in the longi-
tudinal direction of the needles, and to penetrate into the branch.
Whether the bark of the young branch at the time of the maturity
of the sporidia can be pierced by these is likewise doubtful. There-
fore it may perhaps be presumed that the fungus can easily pene-
trate into the branch if the base of the needle is infected. StiU
another possibility is that the sporidia must infect the young
buds for the next year." Klebahn further stated in 1918 (11)
"For Peridermium strobi it is shown that the needles can become
infected but not that the mycehum grows from the needles into the
bark."
Spaulding (16 p. 147) in January 1912 published the following
brief note concerning his inoculations on white pine: "Greenhouse
inoculations have been made upon young Pinus strohus with
teleutospores secured by inoculation on Ribes americanum with
aecidiospores borne upon imported trees of Pinus strobus.
Inoculations thus made in November, 1910, are now beginning to
give results. One each of the trees inoculated with wounds and
without wounds, is now showing slight swelling such as is so
characteristic of the bHster rust disease." This statement indi-
cates, as Spaulding has recently told the writers, that the inocu-
lations were on the stems. He also said that none of the infected
pines formed the aecial stage, but the pycnia, with exudation of
pycniospores, were produced.
From the results of these investigations by Klebahn and Spauld-
ing one is left in doubt whether infection takes place through the
INFECTION OF PINE WITH BLISTER RUST. 433
leaves, the buds or the stems, ajid in what particular manner.
Judging from other statements in literature on this subject, the
general impression is given that it takes place through the stems.
For instance, Fischer, of Switzerland, (7 p. 435) states: "The
aecidiospores infect the Ribes leaves upon which first uredo then
teleutospores appear; the latter germinate immediately and infect
the young twigs of pines." Spaulding (17 p. 6) says in one of his
earlier papers in 1912, concerning infection: ''The winter spores
are blown from the currant and gooseberry leaves upon which they
are produced to various parts of the white pines in the vicinity.
There they stick to the bark of the young trees or branches and
germinate. The branching threads of the fungus penetrate the
inner bark tissues for some distance, but cause no external sign
of disease until nearly a year after the time of infection". He
makes about the same statements in his excellent bulletin (15
p. 26) on the "Blister Rust of White Pine" published the year
previously, and in 1916 he (18 p. 14) states: "The teliospores falling
upon bark of suitable age on a white pine may in turn germinate,
penetrate the bark and grow in the inner layers during the in-
cubation period already mentioned." Metcalf (14 p. 3) in 1917
makes a similar statement as follows: "The pine blister attacks
white pine seedhngs or pines of any age that have needle-bearing
twigs through which it can enter. The disease spreads from the
twig" etc.
McCubbin, also, writes in 1916 (12 p. 1) "It is believed that the
fungus gains entrance by some wound in the twigs or branches, and
from the point of entrance it grows rapidly up, down and around
the branch in the soft outer bark". In an article written in 1917,
however, he (13 p. 95) questions the branch method of infection
as foUows:
"Only indefinite references to the method of infection of the pine by
Cronartium ribicola have appeared in current literature. From these
references one gathers the impression that infection takes place through
the bark, and probably by way of wounds or abrasions. Having an
opportunity for studying a considerable number of pine infections in
1916, some attention was given to this point and records were made of the
origins of cankers where such origins could be determined.
"In most cases the determination was not difficult, owing to the fact
that in a healthy pine branch the fungus spreads out from the court of
entry in a very legular and equal manner, and that its piogress is marked
by swelling or discoloration or both, or else the cortical tissue is killed in
434 CONNECTICUT EXPERIMENT STATION BULLETIN 214.
an equally radial fashioa. By taking note ot this habit one can readily
locate the point of original infection in most cases, especially in the earlier
stages.
"Very early in this study it became apparent that the chief mode of
infection was by way of leaf fascicles through the so-called short shoots.
In these pines, which were all healthy and which grew in situations where
they were fairly free from accidents, wound infection played but a very
small part.
"According to the tabulated results about 92 per cent, of these young
blister cankers originate in leaf-bundle infection. This percentage in-
cludes only those cases where the point of origin could be confidently
established, but it is highly probable that a large proportion of the num-
ber listed as undertermined should also find a place here, and it might
not be overstepping the mark to ascribe at least 95 per cent, of these
blister cankers to leaf fascicle infection.
"One may consider that the sporidia from the currant leaves are lodged
among the bases of the needles and from this position can then attack the
short shoot which bears these leaves."
PRESENT INVESTIGATIONS.
First Infections. On October 21, 1916, the senior writer
placed infected leaves of Ribes nigrum, having the telial stage,
over two crocks each containing three two-year old seedhngs and
two crocks each containing six one-year old seedlings of Pinus
strohus. These were moistened, covered with bell-jars for several
days and have been kept in the greenhouse ever since. Nothing
suspicious showing during the first month or two, they were not
carefully examined thereafter for some time. On June 14, 1917,
the writers looked them over critically and in one of the crocks
found two of the one year old seedhngs showing conspicuous yel-
low spots which were not seen on the leaves of the other plants.
These two seedhngs also showed the bark slightly swollen and of a
yellowish-green color. On July 14th one of the two year old
seedlings, which had shown nothing very suspicious previously,
was found to be oozing pycniospores in less than nine months after
inoculation. Later a second of these two-year old seedhngs died
and microscopic sections showed pycnia. Several of the young
seedlings were dead by this time, whether from rust or other causes
was not determined. At the present writing two of two-year
old and one of the one-year old seedhngs are still ahve, but show no
signs of infection. Thus out of 18 plants at least 4 were definitely
known to have become infected.
*■ INFECTION OF PINE "WITH BLISTER RUST. 435
Sections of the needles through the yellow spots mentioned
above showed abundance of mycehum which was also found in the
swollen stems and because of this it was uncertain whether the
infection had taken place originally through the leaves or stem.
It was to settle definitely this point that inoculations in the fall of
1917 were again made. These plants were carefully watched from
week to week to obtain the first indications of infection. The
results obtained were verified and extended by other experiments
made in the fall of 1918. Therefore the data given in the following
pages are the combined results of infections made during these
three years.
Methods of Inoculation.
In Greenhouse: Condition of seedlings. Practically all of the
pine 'Seedlings used in the experiments have been grown in crocks
usually from three to ten in a crock, and have been kept ever
since in the greenhouse of the Experiment Station. Some of
these have been grown from seed and others were obtained from
our own and a nearby nursery where bhster rust has never
occurred. No rust either on Ribes or white pines has ever been
found in the vicinity of the Station. Therefore there is absolute
certainty that any infections that have taken place are the results
of our inoculations. Most of the seedlings used have been one,
two or three years old, since for convenience and ease of infection
these have proved most satisfactory. When we speak of one
year old seedlings we mean those of less than a year's growth as
they varied in age from four to eight months. Similarly by those
two and three years old we mean in their second and third year's
development. For the most part these plants have made
excellent growth. As they have been kept in the greenhouse the
year round they have not had the winter rest period of plants grow-
ing outdoors, but during late fall and early winter their growth
has been noticeably retarded. Of course where infection has
taken place in the fall these plants in late winter and early spring
have shown the disease far in advance of those plants infected at
the same time but kept outdoors through the winter. This forc-
ing of the plants and the disease indoors must be taken into con-
sideration, at least as regards time, when comparing with infections
that take place in nature. It is evident from these experiments,
however, that the rate of development of the disease is correlated
with the vigor and rapidity of the growth of the plant.
436 CONNECTICUT EXPERIMENT STATION BULLETIN 214.
Preventive measures. Unless it were desired to keep certain
parts of the plant from becoming infected, the inoculation material
was placed in and aroimd the moistened plants which were kept
covered with a bell jar in subdued Hght for several days. Where
it was aimed to produce infections through definite parts, care was
taken to inclose the inoculation material with damp cotton to
prevent the sporidia from escaping, or else the inoculated part was
left exposed and all the rest of the plant was protected by dry cotton
or paper. Plate XXXVII, fig. 3 shows an example of the latter
condition where spores had been placed on the young leafy shoots
after the rest of the plant had been covered.
Parts inoculated, (a) Stems. The inoculations on the stems
were made in two ways : 1st by cutting a slit in the stem and
inserting the germinating telial column; 2nd by applying the'telial
material to the uninjured stem. In both cases the material on the
part inoculated was wrapped with moist cotton. The cotton also
served to indicate the place of inoculation later on. The stems
used, especially on younger seedlings, were quite small (less than
a quarter of an inch in diameter and were one or two years old)
except in a few cases where the green stem of the present j^ear's
growth on larger plants was used.
(b) Buds. By unopened buds we mean the terminal ones and
in an entirely dormant condition closely enwrapped with the
enveloping brown scarious scales, with no green parts of leaves
exposed. By open buds we included those expanded enough to
show the developing leaves. In both cases especial care was
taken to protect all other parts below from infection by the devices
already mentioned.
(c) Leaves. With inoculation of leaves usually no particular
effort was made to prevent general infection, since infection of the
leaf was determined by the appearance of yellow spots. It was
always possible through microscopical sections of these yellow spots
to find the particular stoma or stomata through which entrance
was gained. There were four different methods used: (1)
placing infected leaves on the soil of the crock, or (2) over the plants
themselves, or (3) still attached to stems stuck in the soil, and (4)
sprinkhng water containing telial material over the plants. In
some cases attempts were made to inoculate special parts of the
leaves as base, centre, or apex, such places being marked by a
string tied at the point of inoculation to identify it for later
INFECTION OF PINE WITH BLISTER RUST. 437
examination (PI. XXXVII, fig. 2). Again, leaves of different ages
were used, as those young and still growing and others one or
two years old. Also the juvenile leaves, such as first appear on
the seedlings (PI XL, fig. 4) or under exceptional conditions on
older plants, were inoculated in comparison with the ordinary
leaves which develop in fascicles of fives on the plants after the
first year.
In Pelrie Dishes. Having been successful with the inoculation
of Ribes leaves in moist Petrie dishes (4 p. 14) it was thought that
this method might be appKed to the pine needles, at least so far
as showing place and method of entrance of the germinating
sporidia. Both juvenile and fascicled leaves were used, the for-
mer on short shoots or on the entire seedling and the latter un-
attached or attached to the stem (PI. XXXVII, fig. 1). Inocula-
tions made in 1917 showed no apparent infection though the
needles were kept in good condition for a month. Possibly the
failure here was due to the fact that the leaves were all of the fas-
cicled form and were kept in the diffused light of the laboratory.
The next year the experunents were extended to young seedlings
and the Petrie dishes this year were kept in the more direct light
of the laboratory greenhouse which faces the east and is protected
from southern exposure to the sun by a wing of the building.
Under Tent. Another method tried was the inoculation of
pines under a tent, to approximate natural methods of infection
without danger of spreading the spores. The tent was made of
unbleached muslin stretched over a frame about four by eight
feet and about six feet high at the ridge. A door on one side made
the examination of the plants easy at any time. To this tent two
black currant bushes had been transplanted to determine if the
Cronartium was carried over on bushes infected the previous
year. Nothing showing in this respect the currants were arti-
ficially inoculated with urediniospores the middle of the summer
of 1918. On August 15, after the appearance of the telial stage,
a wooden box containing numerous small two year old white
pine seedlings was set in the soil under each bush. On October 2,
about a dozen plants from each box were transferred in a bunch to
crocks in the greenhouse to see if forcing the plants during the
winter might have any effect upon the appearance of the (disease.
On September 28 a white pine about a foot high and at least five
years old was also placed under each infected bush.
438 CONNECTICUT EXPERIMENT STATION BULLETIN 214.
Out of Doors. In addition to the preceding, three pines about
three or four feet high and six to eight years old growing in a shel-
tered spot on the Station grounds, and three trees, fifteen to twenty-
feet high and fifteen to twenty years old at the Whittemore
estate in Middlebury, Conn., were also inoculated. In the case
of the pines at the Whittemore estate there was a possibility of
outside infection since Peridermium strohi had been found on
certain of these trees. At both the Experiment Station and at
Middlebury the method used for inoculation was to spray the
branch with water and then to inclose it in a double paper bag in
the inner one of which were placed loosely or sewed to the paper
fresh Rihes leaves infected with the telial stage. A variation of
this method was to spray the leaves with water containing the
germinating teliospores before placing the bag over the branch.
The paper bags were left on the branches from two to four weeks
and in some cases even longer. Except for the longest periods,
living in the bags did not seem to injure the leaves to any appre-
ciable extent. These experiments at both places were carried on in
1917 and again on other branches or trees in 1918. Altogether in
the two years nine branches at the Experiment Station and thirty-
one at the Whittemore estate were inoculated.
General Results of Inoculation.
Out of Doors. Of the forty branches inoculated at the Ex-
periment Station grounds and at the Whittemore estate twenty
were made each year. Despite these many attempts not a single
inoculation was successful so far as can be determined at the present
time (July 9, 1919) . Those made in 1917 were certainly old enough
to show some sign of infection if successful. Close watch has been
kept for indication of yellow spots on the leaves so characteristic
of greenhouse infection, without any evidence of the same. Some-
what suspicious spots have been sectioned for decisive proof of the
presence of the mycelium but also without result.
. To some this might indicate that in nature infection does not
take place through the leaves, but to the writers it is more of an
indication that the methods of inoculation were faulty, since there
is no evidence of any infection through the young stems or buds
which were equally exposed with the needles. The age of the
leaves could not have been the limiting factor, since leaves nearly
two years old (about their age limit) were abundantly infected on
INFECTION OF PINE "WITH BLISTER RUST. 439
the young trees in the greenhouse. It is uncertain whether these
apparent failures were due to rapid decline of the inoculating
material after being placed in the bags, to unfavorable conditions
of moisture or temperature, or to some other unknown factor.
In our greenhouse experiments we have had great variations in
results of inoculations due to conditions which we have not
always been able to explain. We speak of these outdoor inocula-
tions as failures since in the greenhouse experiments some sign of
infection visible to the eye has always shown within one to six
months after the inoculation if successful.
Under Tent. On October 2, at the time of the transference of
part of the two year seedlings from the box under the tent to
crocks in the greenhouse, no sign of infection was visible on the
leaves. On November 8 a single very inconspicuous yellow spot,
evident only under the lens, was found on one of the plants in the
tent and this on sectioning showed the characteristic mycelial
masses. A day or two previous similar spots had been found
on four of the plants transferred to the greenhouse.
During the winter the seedlings in the tent showed little evidence
of further development of the fungus. For example, on February
24 only a few spots were seen on the leaves. These were scarcely
visible to the naked eye, being about one-fourth of a millimeter
long, directly over the stomates and not encircling the leaf as yet.
In comparison with the spots on the plants transferred to the green-
house they were very much less developed. On May 24, however,
these spots were more numerous and were evident to the naked eye,
some of them encircling the leaf while others were scarcely visible.
One plant showed fourteen leaves with these spots and the stem
had already become invaded. A very large percentage of the
plants apparently were infected. Unfortunately a number of the
plants had been winter-killed and during June a severe hot period
killed most of the remaining ones, only four being alive in July.
This greatly interfered with determining just how far advanced
these spots on out of door plants would be at this time of the year,
but those that were present were not very striking. These experi-
ments would indicate that infection in nature, which takes place
in the fall, is very inconspicuous and may entirely escape detection
at that time, and that the spots develop rather slowly during the
spring, perhaps in cases not becoming conspicuous until the
middle of July.
440 CONNECTICUT EXPERIMENT STATION BULLETIN 214.
On the other hand the plants that were transferred October 2
to the greenhouse continued to develop, at first slowly during the
late fall and early winter. By Novenber 26 at least seven out of
the fifteen plants in one crock and all eight plants in the other
crock showed inconspicuous spots indicating infection. By
January 28 the spots were more conspicuous, in cases six to ten
showing on a single plant. At this time the spots were one-
sixteenth of an inch long and barely encircling the leaf. In one
plant a slight swelling and yellowing of the stem indicated infection
there had already taken place. From February 20 to the middle
of March these spots became quite conspicuous, usually one to four
mm. long and entirely encircling the leaf. The average spot was
about two mm. long. In cases where infections had taken place
close together these golden-yellow spots were merging. By the
last of March it was evident that nineteen out of the twenty-
three plants transferred had these infections on the leaves and
their appearance was in strong contrast to those that had been
left in the tent during the winter, showing how the favorable green-
house conditions had hastened the development of the fungus.
By July 1 the spots were about 2-3 mm. in length, though by
merging some were even 6 mm. long. However by this time the
spots were past their prime as some of the leaves containing them
were dying or drying up. At least one plant was dead and on
some of the others the new shoots were killed. It seems evident
that, while a few have formed pycnia, none will survive to form
aecia.
The two large white pines placed in the tent on September 28
on the date of the last examination (July 8, 1919) failed to show
any certain sign of infection. If such had taken place the yel-
low spots on the leaves have remained obscure. These plants of
course were transplanted in the tent much later than the seedlings
and were not directly under the bushes, as were the former, so
that the conditions for infection were not so favorable.
In Petrie Dishes. Of a score or more of inoculations' in Petrie
dishes with the pine leaves, both of the fascicled and juvenile
forms, we were successful in only two experiments. One of these
was on very young seedlings and the other on shoots having
juvenile formed leaves. In no case were we able to detect infec-
tion on the fascicled leaves. Even on the juvenile leaves the
spots were so shght as to require careful inspection with a lens to
INFECTION OF PINE WITH BLISTER EUST. 441
determine their presence. Four out of six seedlings in one case
showed a few spots which were identified by microscopical sec-
tions as containing the rust. Of the five shoots in the other case,
infection was positive in two and probably in two more. All these
infections were first identified about five weeks after inoculation
by which time most of the Petrie dish cultures were usually in
poor condition through molds, etc. These spots were first visible
somewhat later than the earhest signs found in potted plants in
the greenhouse. The length of time required after inoculation
before infection shows makes this a rather unsatisfactory method
for telial inoculation as compared with the same method for inocu-
lation on Ribes leaves.
In Greenhouse, (a) Stems. In the two years, inoculations were
made on thirty-five cut and fourteen uncut stems and not a single
one of these forty-nine cases has shown any evidence that the
inoculation was successful. This seems somewhat contradictory
to the results obtained by investigators with other species and
with the apparent result obtained by Spaulding with this method.
We are not certain whether the latter used any precautions in
preventing infection through the leaves. We do not wish to state
positively that infection cannot take place through the stem, either
wounded or unwounded, because we were unsuccessful in our
attempts. Possibly the small size of the stems through which we
attempted inoculations may have had something to do with the
failure. There is no question that on very vigorous green shoots
stomata occasionally occur and it is not impossible that the germ
tubes of sporidia may gain entrance through them. Their small
number and the difficulty of the sporidia sticking to the stem,
however, would make the chance of infection slight as compared
with that of the leaves.
(b) Buds. During the two years inoculations were made on the
opened buds of twelve plants, seven of which were successful.
On the unopened buds fourteen inoculations were made in 1917
and ten in 1918. Of these only two were successful, both made in
1917, and it is not certain whether these buds can be strictly
considered as unopened. Our classification of buds as opened
and unopened, too, in 1917 was not so clear cut as in 1918. In one
of the plants the permanent sHde shows, by the presence of a
definite sclerotial mass some distance from the base, that infec-
tion took place through a scale which had become elongated,
442 CONNECTICUT EXPERIMENT STATION BULLETIN 214.
green and needle-like. In the other plant evidence is lacking how
infection took place as sections were not made until the tissues
of the young stem had become thoroughly invaded.
From the results of these experiments it seems that infection
can readily take place through opening buds or shoots which have
exposed leaves containing stomata. On the other hand it seems
quite certain that infection does not take place through an
unopened bud closely enwrapped by the scarious brown scales. In
some cases these scales, however, continue their development into
modified leaves and, through the stomata of such, infection no
doubt may take place as in the case cited above.
(c) Leaves. As has just been noted infection readily took place
through the leaves. In fact so far as we can determine of the one
hundred successful inoculations reported in Table 6 all, except
in the two very doubtful eases already cited, were traceable to
leaf infection. The very first sign of infection to the naked eye,
visible usually about a month or two after inoculation, or even
earlier with a hand lens, is a very small yellowish spot centering
in the lines of stomata that run lengthwise of the leaf (PI. XL,
fig. 3). These infected leaves later showed evident golden-yellow
encircling spots (PI. XL, figs. 1-2) which were filled with character-
istic sclerotial masses of the fungus, even when there was no myce-
lium in the stem. Eventually, however, it appeared there at the
base of these infected leaves. Sections through the yellow spots
also definitely proved that infection took place through the stomata-
as indicated by a characteristic substomatal vescicle directly
below the guard cells. Details of infection and the nature of the
substomatal vescicle will be discussed later. Suffice it to say here
that there was always found in microscopic sections of the yellow
spot, usually about the center and beneath a stoma, a substomatal
vescicle with a primary hypha leading down to the sclerotial mass
(PI. XLI, fig. 2; PI. XLIII, figs. 1-6). For example, in one leaf
nineteen distinct yellow spots were counted and sections of this
leaf showed at least twenty-one substomatal vescicles. In some
cases the number of infections as indicated by yellow spots was
obscured by the latter running together (PL XL, fig. 6) and in a
few instances we found two substomatal vescicles below one
stoma signifying two infections at this place.
So far as types of leaves are concerned infections were secured
readily through both the juvenile and fascicled forms. The former
INFECTION OF PINE WITH BLISTER RUST. 443
because of their flattened and somewhat grooved upper surface,
thereby more readily retaining sporidia, are perhaps somewhat
easier infected. As to age we succeeded in infecting leaves from
the very young juvenile stage to those of fascicled form one and
even nearly two years old. There did not seem to be any difference
as to the part of the leaf involved (base, middle or apex) since
infection readily took place all over (PI. XL, fig. 1), except that
the bases of the leaves may have afforded better chances for the
sporidia to adhere.
Quite variable results were obtained with different methods of
inoculation. The most successful was the one in which the Rihes
stems with fresh infected leaves were stuck in the crock over the
pines. This method approaches nearest to natural conditions.
Of thirty-six plants in eight different crocks inoculated on Oct. 19
and 22, 1918, all but one were infected. Not only was this high
percentage of infection secured but the many yellow spots on the
leaves showed that the infections had been very numerous on
each plant. Of these plants fifteen were three years old and
twenty-one were seedlings of less than six months. Infections
of the latter was so severe that at the present writing practically
all have been killed. Fair results were also obtained where water
containing tehal colum.ns was sprinkled over the plants especially
those containing young shoots. The poorest results were given
where the infected leaves were put on the soil under the pines,
only one out of ninety plants becoming infected. Where such
leaves were placed over the pines the results were better.
Percentage of infection does not alone explain the value of the
method employed, since a single plant infected through a single
leaf is not comparable to another plant infected through many
places on numerous leaves. While the method of infection may
have had considerable to do with the results obtained, the time
of infection also seems to have been a factor. During the two years,
on the whole, the best results were obtained during October.
Infections, however, may take place at any time sporidia are
produced in good condition, since we infected a plant in one
instance in June.
Age of Plants. Out of two hundred and thirteen plants inocu-
lated in 1917, one hundred and thirty-three were one year, and
eighty were two j^ears old; and of the twenty-four resulting
infections eighteen were one year and six two-year old pines. In
444
CONNECTICUT
EXPERIMENT
STATION BULLETIN 214
.
I
1
Table VI — Geeenhousb Inoculations
Inf. Ribes
Inf. Ribes
Inf. Ribes
Total
Total inf.
Inf. Ribes
leaves
leaves on soil
branches in soil
Date
No.
plants
inoc.
leaves on soil.
over plants.
and over plants
and spreading
over plants.
No.
No.
No.
No.
No.
No.
No.
No.
No.
per cent.
inoc.
inf.
inoc.
inf.
inoc.
inf.
inoc.
inf.
1916
Oct. 21
18
4
22
18
4
1917
Aug. 25
21
0
0
16
0
Aug. 27
9
0
0
Sept. 6
57
3
5
32
'6
ie
'3
Sept. 12
11
0
0
Sept. 14
5
0
0
'5
'6
Sept. 24
9
0
0
9
0
. .
Oct. 15
21
4
19
10
1
Oct. 16
8
4
50
Oct. 17
61
13
21
Nov. 1
11
0
0
ii
0
• •
Total...
213
24
11
83
1
0
0
16
3
0
0
1918
June 13
1
1
100
,
Sept. 30
12
0
0
7
'6
'5
'6
Oct. 1
48
9
19
Oct. 2
6
3
50
Oct, 5
11
1
9
ii
'i
Oct. 7
4
1
25
Oct. 8
to
2
20
Oct. 9
18
6
33
9
3
'2
i
Oct. 10
5
2
40
2
0
Oct. 11
35
10
28
Oct. 19
28
28
100
28
28
Oct. 22
8
7
87
8
7
Oct. 26
2
2
100
Oct. 29
2
0
0
Oct. 30
3
0
0
"3
'6
Total. . .
193
72
37
7
0
14
3
18
2
36
35
Total
for3yrs.
424
100
23
90
1
14
3
52
9
36
35
1918 of the one hundred and nmety-three pines inoculated (not
including the twenty-three inoculated in tent and later transferred
to greenhouse) fifty-eight were one year, thirty-six two years, and
ninety-nine three years old. This year seventy-two plants became
infected, twenty-nine of the one year, four of the two years and
thirty-nine of those three years old. While these embraced the
Yl
irious
met
hods 0
fir
lOCl
ilat
ionj
th
ey
wei
-e E
LOt exa
ctly th
le
3am
e
i
-
INFECTION OF
OP Cronariium
PINE WITH
ribicola on
BLISTER RUST.
Pinus sirobus.
445
III spores on
def. spots on
pine leaves
III spores
sprayed over
plants.
III spores
sprayed over
young shoots.
III spores on Buds.
III spores on Stems.
opened.
unopened.
cut.
uncut.
1 No.
1 inoc.
No.
inf.
No.
inoc.
No.
inf.
No.
inoc.
No.
inf.
No.
inoc.
No.
inf.
No.
inoc.
No.
inf.
No.
inoc.
No.
inf.
No.
inoc.
No.
inf.
6
3
3
6
'8
19
0
0
0
0
°4
0
2(
)
9
'5
"5
'3
'2
'3
6
'5
'6
0
2(?)
'3
'5
'3
i2
'6
'6
'6
'6
3
6
\ 44
4
20
9
0
0
10
5
14
2(?)
23
0
3
0
1
2
2
3
2
3
3
4
0
2
2
0
1
i2
'4
2i
"2
2
1
5
1
5
2
0
3
2
3
3
2
3
2
2
'4
"4
'2
'6
'6
'0
]
[
)
)
)
8
3
6
6
33
8
42
14
8
8
2
2
10
0
12
0
11
0
77
12
62
23
8
8
12
7
24
2(?)
35
0
14
0
i
f(
a
y
ti
0
p
)rt
ffec
ear
on.
f th
er (
rere
he
tec
th
I
e c
3en
m
difl
I s
e c
^or
)ne
t.c
uc
'er
on
ne
in
y
fi
ti ]
ent
lew
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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.
^. ■'
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CROSS SECTIONS OF INFECTED PINE LEAVES.
PLATE XLIV.
TELIAL STAGE AND ITS GERMINATION.
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