U. S. DEPARTMENT OF AGRICULTURE.
BUREAU OF PLANT INDUSTRY— BULLETIN No. 63.

K. T. GALLOWAY, Chief o) Bureau.

INVESTIGATIONS OF RUSTS.

MARK ALFRED (ARLETON,
Cerealist in Charge op Cereal Investigations.

VEGETABLE PATHOLOGICAL AND PHYSIOLOGICAL
INVESTIGATIONS.

Issued Julv 12, 1904.

WASHINGTON:
government printing office.

1904.

Jfl; Mtntk

Glass $ &JJ.%J_
Book yKl> C^

76

3 6

i'if

Bui. 63, Bureau of Plant Industry, U. S Dept. of Agriculture.

Plate I.

A Perennial Rust.
C/Ecidium Tuberculatum E.& K.on Callirrhoe involucrata Gr.)

U. S.' DEPARTMENT OF AGRICULTURE.

BUREAU OF PLANT INDUSTRY— BULLETIN No. 63.

B. T. GALLOWAY, Chief of Bureau.

INVESTIGATIONS OF RUSTS.

MARK ALFRED CARLETON,
If
Cerealist in Charge of Cereal Investigations.

VEGETABLE PATHOLOGICAL AND PHYSIOLOGICAL
INVESTIGATIONS.

Issued July 12, liJO-1.

WASHINGTON:

GOVERNMENT PRINTING OFFICE.

1904.

BUREAU OF PLANT INDUSTRY.

B. T. Galloway, Chief.
J. E. Rockwell, Editor.

VEGETABLE PATHOLOGICAL AND PHYSIOLOGICAL INVESTIGATIONS.

SCIENTIFIC STAFF.

Albert F. Woods, Pathologist and Physiologist.

Erwin F. Smith, Pathologist in Charge of Laboratory of Plant Pathology.

George T. Moore, Physiologist in Charge of Laboratory of Plant Physiology.

Herbert J. Webber, Physiologist in Charge of Laboratory of Plant Breeding.

Walter T. Swingle, Physiologist in Chary*' of Laboratory of Plant Life History.

Newton B. Pierce, Pathologist in Charge of Pacific Coast Laboratory.

M. B. Waite, Pathologist in ('ha rye of Investigations of Diseases of Orchard Fruits.

Mark Alfred Carleton, Cerealist in Charge of Cereal Investigations.

Hermann yon Schrenk," In Charge of Mississippi Valley Laboratory.

P. H. Rolfs, Pathologist in Charge of Subtropical Laboratory.

C O. Townsend, Pathologist in Charge of Sugar Beet Investigations.

P. H. Dorsett, Pathologist.

Rodney H. True, & Physiologist.

T. H. Kearney, Physiologist, Plant Breeding.

Cornelius L. Shear, Pathologist.

William A. Orton, Pathologist.

W. M. Scott, Pathologist.

Joseph S. Chamberlain, Physiological Chemist, Cereal Investigations.

R. E. B. McKenney, Physiologist.

Flora W. Patterson, Mycologist.

Charles P. Hartley, Assistant in Physiology, Plant Breeding.

Karl F. Kellerman, Assistant in Physiology.

Deane B. Swingle, Assistant in Pathology.

A. W. Edson, Scientific Assistant, Plant Breeding.

Jesse B. Norton, Assistant in Physiology, Plant Breeding.

James B. Rorer, Assistant in Pathology.

Lloyd S. Tennv, Assistant in Pathology.

George G. Heogcock, Assistant in Pathology.

Pem.ey Srwi riiNG, 'Scientific Assistant.

['. J. O'Gara, Scientific Assistant.

A. D. S'lAMEL, .Sc:,:iltlic Assistant, Plant Breeding.

T. h\u.pH Poiu.nscn, Scientific Assistant. Plant Physiology.

Florence Hedges, Scientific Assistant, Bacteriology.

Charles J. Brand, Scientific Assistant in Physiology, Plant Life History.

a Detailed to the Bureau of Forestry.

''Detailed to Botanical Investigations and Experiments.

I

JAN

*o%!9<>?

^>

LETTER OF TRANSMITTAL

IL- S. Department of Agriculture,

Bureau of Plant Industry,

Office of the Chief,
Washington, I>. C, April W, WOJ,.
Sir: I have the honor to transmit herewith the manuscript of a
technical paper entitled "Investigations of Rusts,"' by Mark Alfred
Carleton, Cereal ist in Charge of Cereal Investigations, Vegetable
Pathological and Physiological Investigations, and recommend its
publication as Bulletin No. 63 of the series of this Bureau.

The two illustrations accompanying the manuscript are necessary
to a complete understanding of the subject-matter of this paper.
Respectfully,

B. T. GALLOWrAY,

Chief of Bureau.
Hon. James Wilson,

Secretary of Agricultun .

3

PREFACE

The experiments and obsei v.ui .!... on rusts which are the basis of
the following' notes were begun by Mr. Carleton several years ago,
and were continued at intervals until the spring of 1900, when the
pressure of other duties prevented further work of this kind up to
the present time. The results obtained in many instances are still
incomplete, but an1 of sufficient value to be recorded. Some of the
species studied are of much economic importance. The investigation
is a continuation of the work reported in Bulletin 16 of the Division
of Vegetable Physiology and Pathology, and is concerned chiefly with
the segregation of rust forms of economic importance on the common
grasses and the completion of the life history of certain species. The
work is to be carried on more extensively during 1904.

A. F. Woods,
Pathologist and Physiologist.
Office of Vegetable Pathological and

Physiological Investigations,

Washington, 1>. ('.. March26, 1904,.

5

CONTENTS.

page.

Additions to our knowledge of life histories 9

Euphorbia rust ( Uromyces euphorbise. C. and P.) 9

Sunflower rust ( Puccinia helianihi Schw.) H

Crown rust of oats ( Puccinia rhamni [Pers.] Wettst. ) 13

Segregation of host plants ^

Black stem rust of Agropyron and Elymus 15

Orange leaf rust of Agropyron and Elymus 17

Black stem rust of Agrostis alba vulgaris 1'

Rust of Chloris {Puccinia chloridis Diet.) 18

Rusts of willow and Cottonwood (Melampsora) 18

Winter resistance of the uredo 19

I'redo of Kentucky bluegrass rust (Puccinia poarum Niels. ) 20

Uredo of Puccinia montanensis Ell ; 20

Emergency adaptations 21

Puccinia vexans Pari "-

Experiments with Lepto-uredinese 25

Rust of cocklebur (Puccinia xanthii Schw.) 20

Rust of velvet leaf ( Puccinia heterospora P>. and C.) 20

Perennial species -•

JEcidium tuberculatum E. and K 2/

Rust of Peucedanum famiculacevm 2<S

Description of plates ^

ILLUSTRATIONS

Page.

Plate I. A perennial rust Frontispiece.

II. Rusts of Euphorbia and grama urrass — 32

B. P. r.— 102. V. P. P. I.— 117.

INVESTIGATIONS OF RUSTS.

ADDITIONS TO OUR KNOWLEDGE OF LIFE HISTORIES.

In many instances, without an}' experimental proof, it is inferred
that there is a connection between the different forms of rust occur-
ring on the same host plant simply because of their constant associa-
tion with each other. Sometimes it is afterwards demonstrated that
these inferences are wrong, though they are probably correct in a
majority of cases. Studies of the following species were made with
tin1 view of obtaining a more accurate knowledge of their life history.

Euphorbia Rust (Uromyces eup/wrMa C. and P.).

Until the experiments herein described were performed it had not
been demonstrated that there is any connection between the a'cidial
and other stages of this species, although experience naturally leads
one to think that there is. They are in very close association on the
same plant, the secidium appearing first, quickly followed by the
uredospores. In the spring of 1893 Mr. J. B. S. Norton, now pro-
fessor of botany at the Maryland Agricultural College, while engaged
in experiments in the germination of weeds in the greenhouses of the
Agricultural Experiment Station at Manhattan, Kans., called the
writer's attention to a very young rusted seedling of Euphorbia dentata.
In this instance, as is usually the case with the young plants of this
host, the pods were first badly affected by secidia. This fact, taken
together with the common observation that the seed pods of this host
are usually affected Irv all stages of the rust, led at once to the thought
that it was a case of rust propagation through the medium of the germi-
nating seed of the host, something not before demonstrated for any
other species in the entire group of Uredinea?, so far as the writer
knows, unless we except the single instance of the experiments of
Doctor Eriksson" with Puccinia glumarum.b The seed used by Mr.

a Vie latente et plasmatique <le certaines Ur^dinees. Compt. Rend., lSit?, pp.
475-477.

'' T. S. Ralph, in Victorian Naturalist, Vol. VII, p. 18, describes an instance of a
rust attacking the seed of Senecio vulgaris, stating that "with the microscope we are
able to trace the fine yellow sporular matter into the covering of the seed, and into
the seed itself;" but apparently it was not determined by further investigation
whether or not the rust was utile to reproduce itself through the germinating seed.

9

10 INVESTIGATIONS OF RUSTS.

Norton was examined and the pods were found to be badly affected.
Moreover, he stated that the seeds were planted without shelling. But
the writer did not know then, as he does now, that this fact would
probably make little difference, since the nuked seeds are commonly
affected, often showing1 actual peridia.

To test the theory of rust propagation above mentioned, experiments
were instituted on April 22 for growing plants from rusted seed under
a bell jar. The seed used bore all stages of the rust. The experiments
were in five series: (1) Seeds shelled and disinfected by mercuric
ehlorid; (2) seeds unshelled and disinfected; (3) seeds shelled, but not
disinfected; (1) seeds unshelled, not disinfected; (5) like series No. 1,
but rusted mainly with ajcidium. All were planted in pots in a
greenhouse and the pots were kept under bell jars. On May 1 the
plants began to come up. After about three months, when the plants
had grown to a height of 3 to 5 inches, no rust had appeared on series
1 and 2, and only one spot on one plant of series 3. The plants of
series 1 and 5 were much rusted, the aecidium appearing first, fol-
lowed shortly by uredosori.

On April 25, 1893, it was attempted to germinate teleutospores of
rust from the seeds used in these experiments, in water-drop cultures,
which resulted in failure. On June 28, 1893, a similar culture of the
fresh uredospores failed to germinate in two days.

In 1895 rusted seeds of Euphorbia dentata, sent from Kansas, were
planted in the greenhouse of the Department of Agriculture, at Wash-
ington, D. C. From these three plants grew, which were kept under
a bell jar. Soon one of these plants rusted badly, first with the secid-
ium, then a slight amount of the uredospores, and later the teleuto-
spores. It should be remarked here that F^uphorbia rust, so far as
reported, occurs only on E. maculata in the vicinity of Washington,
D. C, and the writer has never yet been able to obtain rusted seeds in
that region.

On December 11, 189(3, a third series of experiments was started at
Washington, D. C. On that date rusted seeds of Euphorbia <l<nt<if<t
from Kingman and Manhattan, Kans., were planted and kept under a
bell jar as before. Eleven plants resulted by December 26. On March
8, 1897, spermogonia appeared in considerable amount on the young
leaves of one plant, with a tendency to form a sort of hexenbesen.

On March 29 two more plants were rusted, one with spermogonia
only on the young leaves, and the other with aecidia on the fruit.
On April 10 still another plant showed spermogonia, making four in
all, out of the eleven, that became rusted. (See PI. II, fig. 1.)

As above stated, the proof that the rust actually penetrates the hulled
seed is readily obtained, not only from microscopical demonstration,
but also from the fact that the actual peridia may often be seen with
the unaided eye in the seed. These experiments, however, further

SUNFLOWER RUST. 11

demonstrate the ability of the rust to propagate itself through the
medium of the germinating seed of the host, and also make it seem
probable that this is even the common method of reproduction in the
case of its occurrence on Euphorbia d&ntata.

It will be noted also that the results of these experiments make it
almost certain that the xEcidium and Urom}Tces appearing upon the
plants are one and the same species, since in every case all stages
resulted from planting the rusted seeds, the a?cidium appearing first,
then the uredo, and then the teleutospores. If anything was lacking,
however, the proof has since been made complete by the experiments
of Dr. J. C. Arthur, as reported in the Botanical Gazette/ in which
the uredospores and teleutospores were obtained on Euphorbia nut mix
from a sowing of a'cidiospores from other plants of the same host on
June 20, 189!).

As is wrell known, the Euphorbia rust is widely distributed over the
United States, occurring on numerous host species, but it is probably
most abundant on E. dentata and E. preslil. It is a significant fact,
bearing upon the ontogeny of the species, that it is also on these two
hosts, particularly on E. dentata, that the secidium is most common,
and that the rust attacks the seed so severely. The seed pods are also
affected considerably in the cases of E. lata and E. marginata.

On June li!, 1897, a?cidiospores of this rust had germinated very
well in water-drop culture after three days, and on June 22, after a
two days' culture in water of both the a?eidium and uredo from
Euphorbia marginata, the latter germinated sparingly, but the former
not at all. In no instance could the teleutospores be germinated,
chough germination was not attempted very often.

The writer has collected all three stages of this rust on Euphorbia

naculata, E. marginata, K. dentata, E. presHi, E. glyptosperma, and

E. heterophylla. On E. petaloidea and E. serpyllifolia only the uredo

and teleuto stages were found, and on E. lata and what was probably

E. geyeri even the uredo was rarely seen.

Sunflower Rust {Pucoinia helianthi Scnw.).

Although Saccardo rightly regards this species of- Schweinitz as
quite distinct, and includes with it the iEcidium often associated on the
same host, in many herbaria the authority of Winter and Burrill is
followed in making it a form of Pucoinia tanaceti, while the iEcidium
is commonly referred to vEcidium compositarum, a convenient dump-
ing ground for numerous uncertain forms. The writer has always
considered this disposition of the species to be without any good
reason even on a purely morphological basis, and now the experiments

"Arthur, J. C, "Cultures of Uredineee in 1899," Bot. Gaz., Vol. XXIX, No. 4,
pp. 270-271, April, 1900.

12 INVESTIGATIONS OF RUSTS.

here recorded make it rather certain that Schweinitz and Saccardo are
correct. So far as this country is concerned, the writer is convinced
that P. tanaceti either belongs almost entirely to tanacetum or does
not exist at all. So far it has been utterly impossible, even in a green-
house, to make transfers of the uredo from one to another of the
numerous supposed hosts of that species, except among- hosts of the
same genus. a It is, at any rate, pretty certain that the forms occurring
on Vernon ia, Helianthus, Actinella, and Aplopappus, which have been
referred to 1\ tanaceti at various times, should be considered distinct.

The circumstances connected with the culture experiments with this
species wTere in themselves peculiar. Late in the autumn of 1897 at
Manhattan, Kans., it was desired to obtain fresh material of the uredo
for inoculating various hosts, but at that date very little else than the
teleuto stage could be found. Finally, on October 29 a small amount
was found on Helianthus petiolaris, mixed among a much larger quan-
tity of teleutospores, and from this material sowings were made on II
j), tiolaris and //. annuus. On November 8 there resulted one rust spot
on the latter host and three on the former. The spots were of the
uredo stage, but the interesting feature accompanying this culture was
the appearance first of spermogonia in one of the spots. This fact
made it probable that a part of the infection resulted from the teleuto-
spores of the inoculating material, even at this unusual season for the
germination of these spores. On March 7, 1898, while stationed at
the University of Nebraska, inoculations of II petiolaris were again
made with the teleutospores only from other plants of the same host,
from which numerous spermogonia appeared in eight days, followed
shortl}r by a3cidia, which were fully developed by November 1. Ify
these results the connection of the different stages of the rust is pretty
well established. At the same time it is shown that the forms on
II. petiolaris and II. annuus are identical. In all cultures made of
this rust both the uredospores and teleutospores have been found to
germinate easil}T and produce infections readily. Reverse cultures
with a'cidiospores were not made.

These experiments were first reported at the 1900 meeting of the
Society for Plant Morphology and Physiology, at Baltimore. Since
that time Drs. J. C. Arthur''' and W. A. Kellerman'' have made a
number of such experiments, confirming these results, but also seem-
ing to indicate a distinction of host forms on different species of sun-

" Dr. M. Voronin at first also obtained negative results in similar experiments in
Russia in attempting transfers of the rust on to other hosts. (See Bot. Zeitung, vol.
30, pp. 694-698, Sept. 27, 1872.) Later he obtained infections of Puccinia tanaceti
from Tanacetum vulgare on sunflower, which, however, did not produce such vigorous
growth as ordinarily. (Bot. Zeitung, vol. 33, pp. 340,341, May 14, 1875. )

''Botanical Gazette, vol. 35, p. 17, January, 1903; Journal of Mycology, vol. 10,
pp. 12-13, January, 1904.

c Journal of Mycology, vol. 9, pp. 230-232, December, 1903.

CROWN RUST OF OATS. 13

flower. Doctor Voronin, in his experiments above mentioned, also
found that rust of cultivated sunflower would not infect Helianthus
tuberosus. In 1901 Ernst Jackya inoculated the following hosts with
teleutospores from Helianthus annuus : II. annuus, II. oucumerifolius,
II. californicxis, II. tuberosus, II. maximiliana, II. multiflorus, II.
scaberimus, and //. rigidus, with resulting infections of the three first-
named species, but no infection of any of the others.

The evidence from all these experiments just quoted and those of
the writer shows at least that the rusts of Helianthus annuus (includ-
ing cultivated varieties), //. petiolaris, and //. mollis are identical.
with the probability that a distinct form exists on //. tuberosus.

Sunflower rust has been collected by the writer on the following-
species of Helianthus. including all stages on nearly every species:
//. ,ii,n mis (both wild and cultivated), //. rigidus, II. petiolaris, IT.
tuberosus, II. hirsutus, II. maximiliana, II. grosse-serratus, II. orgyalis,
II. mollis, and //. ciliaris. The secidium occurs rarely in compari-
son with the occurrence of other stages, hut is to be found on a num-
ber of hosts and occasionally in considerable abundance. This rarity
of its occurrence, together with the occurrence of spermogonia so
often with the uredo, may be accounted for by the fact that the uredo
is often produced by direct teleutosporic infection.

Crown Rust of Oats (Puccinia rkmm [Pees.] Wettst.).

In a mere note in a previous bulletin of this Department6 it is stated
that certain infections had just been made showing the connection of
the crown rust of oats on Phalaris caroliniana and Arrhenatherum
, hit Ins with the gecidial form on Rhamnus lanceolata. No other dem-
onstration of such a connection of forms had been reported up to that
time. During the same season, however, Doctor Arthur obtained
infections with the secidium of Rhamnus lanceolata on oats at Lafayette,
lnd.'' The experiments of the writer are here ghren in detail.

On August 23, 1S!>7, the uredo stage of a rust, supposed to be Puc-
cinia coronata, was found in great abundance on Phalaris caroliniana
at Stillwater, Okla. This host, with the rust , was transferred to a green-
house of the Agricultural College at Manhattan, Kans., and inocula-
tions were made on oats, wheat, and orchard grass on August 30, 1897,
resulting September 7 in a good infection of oats, a poor one of the
orchard grass, and no infection at all of wheat. Other inoculations
were made September 1 on wheat and rye, with no result. By October
8 the teleutospores had appeared on the original plants of Phalaris

"Central!.. Bakt. Parasit. u. InlVkt., 2 Abt., Bd. 9, No. 21, pp. 802-804, December,
1902.

&Cereal Rusts of the United states, Bui. No. 16, Div. of Veg. Phys. and Path.,
U. S. Dept. of Agriculture, 1899.

'llul. Lab. Nat. Hist. State Univ. Iowa, Vol. TV, pp. 398-400, December, L898,

14 INVESTIGATIONS OF RUSTS.

at Stillwater and were of the crown rust type. After this date the
experiments were continued at the State University laboratories at
Lincoln, Nebr., all host plants then in use being- transferred to that
place. On November 16 the crown rust was found, in the uredo stage,
on Arrhenatherum elatius on the State University farm, and a rusted
plant was transferred to the greenhouse. On December 11 inoculations
with the rust were made on oats and rye, resulting in a good infection
of the former in twelve days, but with no result on the latter. Fur-
ther inoculations of oats with the Phalaris rust on February 16, 1898,
resulted again in a good infection in 9 days.

No species of Rhamnus is native near Lincoln, Nebr., but Rhamnus
lanceolata is rather common at Weeping Water, about 20 miles east of
Lincoln, where it is often badly rusted with iEcidium. From that
place a large amount of the zEeidium was obtained fresh on June 1,
1898. A water-drop culture of the material, made the next day, gave
a profuse germination of the spores in twenty-two hours. Inocula-
tions with the secidiospores on oats and Phalaris caroliniana were
made June 1 and June 2, resulting in a successful infection of Phalaris
on June 11 and of oats on June 18. The oat inoculations were made
simply on detached portions of the plant preserved with their broken
ends in water in a damp chamber. As in all other instances, these
inoculations were made with the greatest of care to prevent accidental
infections. The whole series of experiments proves (1) the connection
of the secidial form of Rhamnus with the crown rust of oats, and (2) the
identity of the latter with the forms on Phalaris caroliniana and
Arrhenatherum chit his, besides making it probable that orchard grass
may also support this species.

SEGREGATION OF HOST PLANTS.

The most important economic results of the study of rusts are likely
to be derived from the investigation of the relationship of the forms on
our common grasses. Such work has already been carried on to some
extent by the writer and partially reported in the bulletin entitled
"Cereal Rusts of the United States.11 A more detailed account of
some of this work will be given here. Because bearing upon the same
question, it seems proper to mention also some experiments with the
rusts of Salix and Populus. Probably the greatest confusion exists
concerning the identity of the different forms on Agropyron and
Elymus, though there is much uncertainty also about those occurring
on Bromus and other genera.

The experiments here described were conducted at Stillwater, Okla..
Manhattan, Kans., Lincoln, Nebr., and Washington, D. C, the host
plants being sometimes transferred from one place to another. Of all
these rusts the one receiving most attention was the black stem rust
of Agropyron and Elymus.

BLACK STEM RUST OF AGROPYRON AND ELYMUS.

15

Black Stem Rust of Agropyron and Elymus.

At least three and probably four different rusts occur on the species
of these two grass genera, and are often so closely associated that
their accurate identification is extremely difficult. Of the herbarium
specimens of these rusts throughout the country, probably not one in
fifty is identified with any certainty. The writer's experiments with
these forms are still incomplete, but a few things at least have been
established. When these grasses are brought under cultivation the
changed conditions and proximity to other grasses and grains cause
them to become much more rusted than is ordinarily the case. In
the cultivated grass plats at the experiment stations in Oklahoma,
Kansas, and Nebraska the rusts were found in great abundance. It
was therefore easy to carry on many culture experiments. These
experiments with the uredospores of black stem rust were sufficiently
numerous to make it desirable to arrange them in the following table:

Table I. — Culture experiments with black stem rust of Agropyron ami Elymus.

Date.

Locality.

( Irigin of inoculating
material.

Plant inoculated.

Period
of incu-
bation
in days.

Result.

Jan. 9, 1897

Washing-ton, D. C.
do

Wheal

Elymus virginicus

Wheat.

10
10
11
11

11
11
6
6
12
8

8
8
16
16
16
16
18
18

Do

do

Do.

Jan. 22, 1897

do

....do

Elymus virginicus

Agropyron richard-
soni.

Do

Do

do...

...do...

Do

Do

do

do

Do

Do

....do ---do ...

Agropyron ocddentdU
Wheat

Sept. 13, 1897 . . .

Stillwater, Okla ...
do

Agropyron tt ru rum . . .

Do

Agropyron tent rum ..

Do

Oct. 5, 1897

Manhattan, Kans .
do

Agropyron ocddentale

Wheat (originally

Agropyrontt nerum).

Do

do ...

Do

do

C).

Do

do

...do...

Agropyron tt nerum . .
Wheat

Oct, 21,1897

do

do

Do

do

...do ...

Do

Do

do

do

(<*).

Do

do

do ...

Rye ..

Do

...do. .

Agropyron ocddentale

Wheat

Rye

Do

Do

do

Tin

Do

do

do

18 Tin

Do

do

...do ...

Agropyron tent rum . .
Agropyron ocddentale
Wheat

18
15
21

Do

Nov. 24,1897 ...

do

Jan. 5, 1898

do

Elymus canadt nsis

glaudfolius.
do

ho >

Do

Jan. 21, 1898

Do

Feb. 11, 1898....

21 Do

do

Wheat (originally
Khi in ii x canadensis
glaudfolius).

10
10

Do.

do

Do

do

Elymus canadt nsis
glaucifolius.

Wheat . . .

11 Do /

Do

do

11 Do

Do

do

do...

Rye ..

Do

do

...do ...

Oats .. .

11
14

11
14

14
14
14

Do

Do

do

...do ...

Eli/mus canadt nsis
glaudfolius.

Ely in u s virgi n /run

muticus.
Elymus intermedius..
Agropyron tenerum ..
Agropyron occidt n-

tale.

Do

do

<1<>

Do

do

. .do

Do

Do

do

...do

Do

Do

Do

do

do ...

Do

do

do ...

Do.

a Pustules differ in color from the original.

^1 pustule only.

c Conditions very unfavorable, however.

rf Apparently 1 pustule formed.

cRust changes color and form of pustule.

/Rust changes color.

16 INVESTIGATIONS OF RUSTS.

Table I. — ( 'ulture experiments with blackslem rust ofAgropyron and Elymus — Continued.

Date.

Locality.

Origin of inoculating
material.

I'limt inoculation.

Period
of incu-
bation

in days.

Result.

Feb. 11, 1898....
Do

Lincoln, Nebr

. ..do

Elymus Virginians

Elymus virgin icus

III III ten*.

Elymus canadensis

glaucifolius.
Agropyron U nt rum. ..
Agropyron occidt n-

tale.

Rye

13
13

13

13

13

13
13

7

11
9

Success.
Do

Hi.

do

Do

I>o

do

Do

Do

do

do

Do

do

do

Do

Do

do

do

Wheat...

Do

do

Wheat (originally
Elymus canadensis
glaucifolius).

Elymus cumuli nsis. . .

Hordt a in jubatum

Wheat

Feb. 25, 1898

do

Do

Feb. 28, 1898

do

Elymus canadensis
glaucifolius.

Do ''

« Pustules differ in eolor from the original.

M;ust changes in appearance.

The results of these experiments, considered in connection with those
recorded in Bulletin No. 16, Division of Vegetable Physiology and
Pathology. U. S. Department of Agriculture, appear to establish two
things, viz, (1) that the forms of black stem rust on wheat, barley,
Hordeum jubatum, Agropyron tent-rum, A. richardsoni, Elymus cana-
densis, and E. canadensis glaucifolius are identical, with the proba-
bility that those on Elymus mrginicus, E virginicus unit /ens, and
Hblcus lanatusa should be included; (2) that the black stem rust of
Agropyron occidentaleb is physiologically distinct from any other.'

A very interesting phenomenon in these experiments was the change
in color and form of sorus of the rust produced by a transference to
another host. In some cases after a transfer the rust was scarcely recog-
nized. The change of color was sometimes from a bright yellow to a
deep brown or orange, or the reverse. The uredo of Agropyron U n< -
rum, for example, was often very yellow on the leaves, but changed to
brown when transferred to wheat. On the species of Elymus the rust
has a brown, waxy appearance, and the teleutospores long remain cov-
ered by the epidermis of the host.

"On January 5, 1900, quite successful infections on wheat were made with the
uredospores of black stem rust of this host.

^ Probably the most correct name of this host, which is known also as Agropyron
spicatum and A. glaucum. (See Hitchcock, "Note on Nomenclature," Science, vol.
17, pi.. 827-828, May 22, 1903.)

'The form on this host was described asadistinct species, named Puccinia agropyri,
by Ellis and Everhart, in Journal of Mycology, Vol. VII, p. 131, March 10, 1892, a
fact not noticed by the writer until after most of these experiments were made.
This species includes Mddxum clematidis D. C. according to Doctor Dietel, the proof
of relationship being the result of culture experiments. (Oesterr. Bot. Zeitschr.,
No. 8, 1892. )

ORANGE LEAF RUST OB' AGROPYRON AND ELYMUS.

17

Orange Leaf Rust of Aoropyron and Elymus.

In the following table are summarized the results of inoculations
with the uredoform of this rust. They were carried on simultaneously
with those of the black stem rust, and the material was taken chiefly
from the same individual host plants.

Table II. — Culture experiments with orange leaf rust of Agropyron and Elymu*.

Date.

Locality.

< irigin of inoculating
material.

Plant inoculated.

Period
of incu-
bation
in da j s.

lie: uli.

Dec 21, 1896...

Washington, !>.<'..
do

Rye

Elymus arm ricanus . . 16
Rye 16

Do

do

Jan. 7, 1897...

...do

do

Elymus virginicus 12

Rye ' 12

Elymus virginicus 13

Rye ' 13

Agropyron richard- 18

soni.
Wheat 18

Do

do

do

Feb 1 1S97...

do

...do

I'M

...do .

do

Feb. 13,1897...

...do ..

Wheat

do

Do

do

Do...

...do...

...do

live

18

12

12

12

12

•jo

26

9

9

9

9

21

21

18

18

11
It
14

1 1

Feb. 20, 1897...

.do

Rye .

Agropyron U nerum. . .

Trilicum viUosum

Elymus canadt nsis. . .
Rye

Do.

Do

...do ...

do

Do.

Do...

...do...

do

Do.

Do

Mar. 80,1897
Do

...do ...

do

.do ...

...do...

Agropyron caninum. .
Rye...

;:;::do

...do

Nov. 3, 1897 ....

Do

Do

Do

...do...

Wheat

do

....do

Do.

do

do

Agropyron tenerum.. .
RVe

Do.

...do ...

...do

Jan. 5, 1898 ...

...do

do

D...

Do

do

do

Wheat '

Failure.

...do ..

Elymus virginicus —
Elymus canadt nsis

glaucifolius.
Wheat.'

Do.

Do

...do

do

Do.

Mar. 12, 1898...

Ii"

Do

Do

do

do

do

do

Elymus canadt nsis . ..

....do

do

Do.

do

do

glaucifolius.
Agropyron tenerum . .

Do.

The chief conclusion to be derived from the results of these cultures
is that the orange leaf rust is very sharply limited in its host adap-
tation and differs widely in this respect from the black stem rust.
Similar results are given in Bulletin No. 16 of the Division of Vege-
table Plrysiology and Pathology, U. 8. Department of Agriculture,
for cultures of the forms on wheat and rye. In fact, it is quite proba-
ble that almost every distinct host species bears a distinct form of the
rust. One of these forms on Elymus virginicus L. has recently been
found by Doctor Arthur to be connected with the iEcidium on Impa-
tiens mil', a Aluhl. and is now to be known as Puccinia impatientis
(Schw.) Arth. '

Black Stem Rust of Agrostis alba vulgaris.

Culture experiments with the uredoform of this rust and observa-
tions in the field indicate that it is distinct and does not occur on other

"Botanical Gazette, vol. 35, pp. 18-19, January, 1903.
27787— No. 63—04 2

18

INVESTIGATIONS OF RUSTS.

hosts.ft The results of the culture experiments are given in the follow-
ing table:

Table III. — Vulture experiments with black stem rust of Agrostis alba vulgaris.

Date.

Locality.

Origin of inoculating , p] t inoculated.
material.

Period
of incu-
bation
in days.

Result.

Dec. 23, 1897...
Do

Lincoln, Nebr

do.

Agrostis alba vulgaris.
do :.

Agrostis alba vulgaris.
Wheat

8
8
8
12
12
14

Success.
Failure.

Do

do

do

Oats

Do.

Jan 24 1898

do

Do.

Do

do

. . .do Oats

Do.

Feb. 11, 1898...

do

Elymus canadensis
glauci Jot ius.

Agrostis alba vulgaris.

Do.

The rust is evidently of the black stem rust group {Purr! nix graminis
of authors), but contains quite a number of abnormal teleutospores,
including mesospores. Many measurements of these spores average
27-54 by 16-23/*, mostly 40-46 by 16-18/*.

Rust of Chloris {Puccinia cMoridis Diet.).

The uredoform of this rust is sometimes very abundant on Chloris
verticillata in the Great Plains region, occurring in late summer and
autumn. The sori are deep brown in color. The uredospores germi-
nate very freely and easily. In a number of experiments made in
1898 it was found that the uredo on 0. vertieillata and C. elegans
would readily transfer from either host to the other, but not to other
grasses, in several cases which were attempted. In a wateh-glass cul-
ture, made March 18, 1898, of uredospores from C. elegans, produced,
from artificial infection in a greenhouse, not only these spores germi-
nated freely, but a number of newly formed teleutospores at the same
time, an occurrence unusual except in the Lepto-uredinea?. Among
thousands of cultures made by the writer only one other instance of
this kind has occurred. In the summer of 1895 at the Biological Lab-
oratory at Cold Spring Harbor, Long Island, both teleutospores and
uredospores taken from the same sorus of a rust on Luzula campestris
gave good germinations/'

Rusts of Willow and Cottonwood (Melampsora).

Both the uredospores and teleutospores of the rusts of willow and
cottonwood germinate readily, the germ tubes of the latter containing
always brilliant endochrome. Health}' leaves of either cottonwood or
willow placed in a clamp chamber have often been infected by the

« Arthur describes culture experiments made by his assistant, William Stuart, in
July, 1898, in which wheat plants were infected with uredospores from this host,
but the spores of the infection eori were larger than those of the. original material.
(Bui. Lab. Nat. Hist. State Univ. Iowa, vol. 4, No. 4, pp. 396-397, 1898.)

;'The species was, without much doubt, Puccinia ohsmra Schroet.

AVINTER RESISTANCE OF THE UREDO. 19

writer in nine to twelve days. The incubation period is much short-
ened by using- germinating spores in tbe inoculations. In the month
of October, at Manhattan, Kans. , an infection was produced in this
way in three days.

It was attempted by numerous inoculations with the uredoform,
chiefly at Washington, D. C, to transfer the rust from willow to Cot-
tonwood and the reverse, but always without success. An interesting-
feature of these experiments was the discover}' of the fact that the
cottonwood most common in Washington, known as South Carolina
poplar, could not be infected by the uredoform from the common
Western cottonwood, though these two poplars are classed by some as
being the same species. Moreover, the rust does not occur in nature
on the South Carolina poplar, but is very abundant on the AVestern
cottonwood, and even occurs in Washington on the few individual
trees of that type growing in the city.

WINTER RESISTANCE OF THE UREDO.

In another bulletin" the writer has given in detail the observations
and culture experiments proving the successful wintering of the uredo
in the orange leaf rust of both wheat and rye. In this connection it
is easy to see a number of closely correlated facts, which may mutually
explain each other: (1) As shown under the preceding topic, the uredo
of black stem rust may infect a number of different hosts, and there-
fore has a manifoldly greater chance of propagation with the same
number of uredospores than if there were but one possible host; (2) as
also shown, the uredo of orange leaf rust is restricted in every case to
but one host, or at most to but one genus, and a much greater produc-
tion of uredospores is therefore necessary for the life of the species
in this stage; (3) as a corresponding matter of fact it is well known
that the uredo of the latter rust exists usually in very much larger
quantity than that of the former; (4) on the other hand, the teleuto-
sporic stage is the prevailing form of the stem rust, which fact makes
this rust usually the more damaging of the two, as the teleutospores
infest the stem chiefly, thus more directly interfering in plant nutri-
tion; (5) the stem rust is proved to be connected with the barberry
rust, thus giving it an additional chance for increased propagation,
and this through the medium of the teleuto stage instead of the uredo;
(6) finally, the uredo being the prevailing form of the leaf rust, and
no secidial form being known in this country,6 it would seem necessary
that this stage of that rust should be very hardy in order to endure
extremes of cold and drought and preserve the life of the species.
Previous investigations of the writer and others have amply proved
that this is the case. In the meantime it is found that in other species

"Cereal Rusts of the United States, Bui. 16, Div. Veg. Phys. and Path., IT. S.
Dept. of Agriculture, pp. 21-23, and 44, 45.

b Except in the case of the form on Elymus virginicus already mentioned.

20

INVESTIGATIONS OF RUSTS.

there exists a similar hardiness of the uredo, of which cases the fol-
lowing will be discussed here:

Uredo oe Kentucky Bluegrass Rust {Puccinia poarum Niels.).

The writer has known for some time that the uredo stage of the blue-
grass rust is able to pass the winter alive and in germinating condition
during any season as far north as Lincoln, Nebr., but additional evi-
dence has been obtained from time to time. At the same time it is sig-
nificant that there is no record that the teleutospores have ever been
found, except in one instance, at the above-named place. In fact, few,
if any, uredoforms so hardy as this one exist in this country. On
February 1. 1893, this uredo was still alive in the vicinity of Man-
hattan, Kans. Every month of the year it exists alive and growing in
great abundance everywhere about Washington, D. C. On March 2,
1898, it was found fresh on green leaves of the host at Lincoln, Nebr.
On the same spot of ground it was still growing and spreading rapidly
on May 8 of the same year. Host plants were transplanted that day
into a greenhouse, where the rust continued to increase rapidly. As
would now be supposed, the rust is sharply limited to its one host,
Kentucky bluegrass. The results of the following cultures may be
given in evidence.

Table IV. — Culture experiments with flic uredo of JCenlucky bluegrass.

Date.

Locality.

Origin of inoculat-
ing material.

Plant inoculated.

Period

of incu-
bation
m days.

Result.

Jan 16 1893

Manhattan, Kans .
...do

Poa pratensis

do

Wheat

18

IS
16

11

11
13

13

is

10

Do.

Oats

D.i.

Dec. 21, 1896....
Jan 22 1897

Washington, D.C..
do

Rye (Until* rubigo-

vera).
Wheat (Uredo gra-

III in is).

do

Do.
Do.

Do

do

Do.

Feb. 1,1897

do

Rye ( Uredo rubigo-

ri ra i.
do

Poa pratensis

Poanemoralis

Poa pratensis

do

Do.

Do...

...do

Do.

Feb. 13, 1897

..do

Wheat ( Uredorubigo-

rcra).

Do.

Feb 25 1897

do

Uredo of Puccinia montane nsis Ell.

This is, in some respects, one of the most interesting of grass rusts.
It is one of the " covered rusts," and is, indeed, so far covered that it
is often entirely overlooked by collectors. The uredosori are very
uniform in size and are exceedingly small, it being necessary often to
examine them, or even rind them, with a hand lens. They are ellip-
tical in shape and placed end to end in long, narrow, yellow striae
between the veins of the leaf. The teleuto stage is so far hidden as
to be detected only by a faintly darker color beneath the leaf epi-
dermis. The rust is the most nearly like P. glumarum Eriks. and

EMERGENCY ADAPTATIONS. 21

Henn. yet found in this country. The known hosts are Elymuscana-
dt nsis&nd K. virginicus, but it seems to occur on other hosts. Whether
the forms on different hosts can be transferred from one to another
is not yet fully determined.

The important fact now known, however, is that the uredoform is
able to preserve the species over the winter without the intervention
of other stages, though it is possible that extensive propagation is
aided by other stages. October 28, 1897, fresh uredosori were observed
on Elymus canadensis at Manhattan, Kans., and again in the same
locality on November 2. But as early in the spring as May 26, at
Lincoln Nebr., when there was yet but a small beginning of vegetation,
the uredo had burst the epidermis of the host in grass plats at the
University farm. Previous to this the living uredo had been observed
in these plats practically every month of the winter.

In other instances the uredospores of certain species are so very
abundant and the teleutospores so rare that there seems a probability
that such species are carried over from summer to summer largely
through the uredo stage alone, though there is no absolute proof of
such a course. Two instances are particularly interesting — those of
the uredos of Puccinia cryptandri Ell. and Barth., and Puccinia on
Panicum autumnale.a The uredospores of these species begin to be
conspicuously abundant about midsummer, but continue in consider-
able abundance until very late in autumn. The uredo of Panicum
autumnalt was found in germinating condition in Kansas up to Novem-
ber 3 in 1897. A water-drop culture of uredospores of this species
gave excellent germination in ten hours August 21, 1897, at Perkins,
Okla. The uredospores of Puccinia cryptandri were found in extreme
abundance in Oklahoma until October 11, 1897, but in all cases with-
out an}T accompanying teleutospores. Often the uredosori had a fresh
appearance on portions of leaves that were quite dead.

EMERGENCY ADAPTATIONS.

In connection with some culture experiments conducted at Lincoln,
Nebr., in the botanical laboratory of the State University, in February,
1898, a water-drop culture was made (February 3) of uredospores of
the above-mentioned Puce! tun cryptandri which had been collected on
October 8, 1897, at Perkins, Okla., and kept to date as herbarium
specimens. A fair germination resulted in twenty-four hours. Spores
from the same collection were used on February 10 to inoculate seed-
lings of Sporobolus airoidesf with the result of the appearance of two
rust spots by March 16. These spots ma}T really have appeared much
earlier and been overlooked, as tbey were very small and the host

« Perhaps a new species, needing further study.

b Apparently this same species of rust had already been collected on Sporobolus
airoides in the same locality where the collection from S. cryptandri was made.

22 INVESTIGATIONS OF RUSTS.

itself is well known to have extremely narrow leaves. Moreover, the
spores were not germinated when applied, and, being from dried .speci-
mens, the incubation period would naturally be long-. Seedlings of
S. cryptandri were not at the time available. On March 16 a second
water-drop culture was made from this dried material, resulting in the
germination of a few spores.

Teleutospores from herbarium specimens have often been germi-
nated, but the writer knows of no other instance of the germination
of dried uredospores, such spores being able also to infect a different
host. These observations and experiments indicate that we have
here a second step in the perfection of the uredo stage as a means of
propagating the species. The first step, the attainment of sufficien
hardiness to continue alive in the green plant, over winter, has just
been discussed. Even in this case the uredo, although quite active,
at least displaces the resting spore, and in a measure performs its part.
But as the perennial host becomes more like an annual and the plant
dies nearly or quite to the ground, as in this particular case of the
Sporobolus (which is quite different in this respect from the evergreen
Poa pratensis, for example), necessarily, in the absence of teleuto-
spores, the uredospore must be able to infect after a dormant period.
The uredospore therefore becomes now practically a resting spore,
but retains the appearance and manner of germination of the summer
spore. Such a modification in form or function of an}7 stage of a
species to correspond with an unusual change of condition of climate
or of the host may be considered as an emergency adaptation.

It is easily understood how the change of conditions may be so
severe as to necessitate still further modification of structure as well
as function, simply as a means of protection. Such a development
seems to have been actually reached in the species next discussed,
which has resulted in the production of a distinct spore form, special-
ized from the uredo, leaving still, however, a tine uredo stage for
summer propagation.

PUCCINIA VEXANS FARL.

There are probably no other species in all the Uredinea? more inter-
esting than this one, and certainly none that has been more perplex-
ing. In this species there are three distinct spore forms aside from an}r
secidium or spermogonium that may possibly exist — true uredo and
teleuto stages, and a peculiar one-celled form different from either of
these. (PI. II, figs. 2-9.) The species was at first made all the more
puzzling by the rarity of the true uredo stage, which was not known
to exist, or at least not reported, until 1890, when Dr. H. J. Webber,
in the Catalogue of the Flora of Nebraska, reported its occurrence in
that State. In certain seasons and localities the teleuto stage also is
almost or entirely lacking.

PUCCINIA VEXANS FARL. 23

The species was tirst described by Peck as a LTromyces ( U. brandegei
Pk.)" on the basis of material collected by Mr. T. 8. Brandege, in
which specimens contained only the third spore form. Because of the
discovery afterwards of two-celled spores associated with this third
spore form, even sometimes in the same sorus, Doctor Farlow described
it as a Puccinia (P. vexans Farl.) in the Proceedings of the American
Academy of Arts and Sciences, Vol. XVIII, pp. 82-83. At that time
the true uredo stage had not been discovered.

This third spore form is far more prevalent than either of the others
as a rule, but is sometimes entirely absent, leaving only the teleuto
stage. It is distinct from either of the other forms in structure and
appearance, and yet resembles both in some respects. It is larger than
either of them, is strongly papillate, and has a much thicker cell wall,
but on the other hand possesses the color and persistence of pedicels
of teleutospores and appears to have pores like the uredospores. (PI.
II, tig. 5.) Doctor Farlow, in his description, says:

A species in which some of the son contain only two-celled spores must certainly
be held to be a Puccinia, and the perplexing question arises, are the one-celled spores
a unilocular form of teleutospores similar to what is known in P. cesatii Schr., or are
they the uredospores of this species? I have not been able to find any other spores
which represent the uredo of the species; and never having seen the unicellular
spores in germination, there is, so far as we yet know, no reason why they may not
be the uredospores. On the other hand, their general appearance and the density
of the cell wall would lead one to suppose that they were of a teleutosporic nature.
Further conjecture is unnecessary, because, as the species is not at all rare in some
localities, botanists who can examine the fungus on the spot ought to be able to
.ascertain whether the one-celled bodies produce promycelia or not, or else to discover
the true uredo of the species.

A full description of all three forms is given by Arthur and Holway
in Descriptions of American Uredinea? accompanying Fasicle IV of
Uredinea? Exsiccata? et Icones.6

After numerous unsuccessful trials during several years, the writer
was finally able to germinate the third spore form, and, as suggested
by Doctor Farlow, has in this way been able to determine its nature.
In manner of germination it is exactly like the uredospore, the long
simple germ tubes being produced through equatorial pores (PI. II,
figs 7 and 8), but is like the teleutospore in germinating only after a
dormant period and exposure to extremes of weather. The uredo and
teleuto forms being already present and morphologically different
from this form, it must be considered distinct. Because of the dual
nature of this spore form, the writer has alreadj^ proposed for it the
name amphispore in a paper read before the Baltimore meeting of the
Society for Plant Morphology and Physiology in 1900, only an abstract
of which was published/' The term has since been adopted by Arthur

aBot. Gaz., 4: 127.

''Bui. Lab. Nat. Hist. State Univ. Iowa, Vol. V, pp. 329-330,

'•Science, Vol. XIII, p. 250.

24 INVESTIGATIONS OF RUSTS.

and Holway," and a second instance of the occurrence of this form is
described by them for Puccinia tripsaci Diet, and Holw. The entire
series of observations and experiments with this species made by the
writer will now be described.

The first cultures of amphispores were made January 15, 1894, at
Manhattan, Kans. . Both a water culture and one of a sterilized decoc-
tion of manure were employed, with no result, the chief cause of fail-
ure being- probably that the experiment was too early in the season.
Afterwards numerous other trials were made with no better success.
In the meantime true uredospores were found on September 25, 1896,
at Manhattan, Kans.

Finally a successful culture of the amphispores was made on March
8, 1897, at Washington, D. C. The germination was excellent. An
abundance of rather long germ tubes, not promycelia, was produced
in forty-two hours, but onl}T one to each spore. These germ tubes,
unlike those of most uredospores, are quite colorless and clear. A few
teleutospores were present, none of which germinated. The culture
was an ordinary water drop, but wTas made in a new form of culture
cell, constructed to special order and similar to the Van Tieghem
cell, except that the glass- ring is quite thin and drawn out into an
open tube on each of two opposite sides, with the opening plugged
with cotton wool, thus admitting sterilized air. This construction may
or may not have increased the chances for germination. The extreme
weather conditions at the time, to which the specimens were first
exposed, probably contributed most to the success of the culture.
They were fastened to the roof of a near-by shed, and after several
days of warm sunshine were thoroughly soaked with rain, which was
followed by snow and then a severe freeze, soon after which the cul-
ture was made. It is an interesting feature of the experiment that
the specimens were received from Dr. David Griffiths, then at Aber-
deen, S. Dak., and had been collected in September, L896, and kept in
the herbarium until sent to Washington. It was unfortunate that
seedlings of the host were not available for making inoculations with
these perfectly viable spores. Such an experiment is yet to be made.

At Manhattan, Kans., in 1897, the uredo was present in considerable
abundance from June until late in October in grass plats on the
Experiment Station farm. On July 8 inoculations were made with
the uredospores of this species and with jEcidium cephalanthi and
^E. xanthoseyli on seedlings of Bouteloua racemosa without result.
Further inoculations with uredospores on October 4 were successful,
rust spots appearing in twelve days (PI. II, fig. 9), followed in nine
more days with one sorus of amphispores. The uredosori are yel-
lowish-brown and rather inconspicuous. On December 31 uredo-
spores could not be found in the grass plats at Manhattan.

"l'.nl. Lab. Nat. Hist., State Univ. Iowa, Vol. V, p. 175.

EXPERIMENTS WITH LEPTOUREDINE^E. 25

At Lincoln, Nebr. , a water-drop culture was made of Puccinia
vexans on March 15, L898, resulting in a few germinations of theteleu-
tospores in three days. Long promycelia were produced, but no
sporidiola. None of the numerous amphispores present germinated.

On September ^9, 1899, all three spore forms were again found in
tin' grass plats at Manhattan. Living host plants were transferred to
Washington, D. C, and seedlings were started for further experi-
ments, when other duties intervened and the work could not be
continued.

Certain facts concerning the relative abundance of the amphispores
and teleutospores in different seasons and localities seem to harmonize
quite well with the idea alread}^ expressed as to the function of the
former. If it is the work of the amphispore to carry the species
through unusually severe cold or drought, then this spore form should
be relatively more abundant in dry periods and relatively more com-
mon to the westward and northward in the Great Plains. These con-
ditions are just what exist. The amphispore prevails almost entirely
in the Dakotas and in western Kansas, western Nebraska, and eastern
Colorado, and appears to have been more common in eastern Kansas
during a dry period of several years than during a wet period. At
the same time westward toward the mountains there is less chance for
an 2Ecidium to connect with the teleuto stage.

EXPERIMENTS WITH LEPTO-UREDINE^.

It is generally supposed that teleutospores which are followed by
an R'cidium germinate only after a considerable period of rest, usually
in early spring. As already mentioned under the discussion of sun-
flower rust, the writer germinated teleutospores of this species readily
in the autumn, and afterwards at different times during- the winter.
This readiness of germination, apparently at almost any date, is an
indication in itself of an alliance to the lepto species. But, more than
this, the autumn inoculations with material in which no uredospores
could positively be detected nevertheless were, in some cases at least,
followed first by spermogonia and then by the uredo! Of course occa-
sional uredospores that may have been overlooked could have produced
those few spots in which the presence of spermogonia was not certain.
Here, then, is further evidence of the lepto tendency of the species.
In addition, it is well known that the eecidium is rare and appears to
have no fixed time of occurrence. Now, only the omission of the
uredo is needed to make the rust a real lepto species. As it is, its
position is more nearly that of a Hemi-puccinia than of an auteecious
species. Experiments of this kind, united with critical held observa-
tions, thus throw much light upon classification as to group position,
as well as enabling us to connect stages.

On the other hand, certain lepto species will be found to closely

26 INVESTIGATIONS OF BUSTS.

approach other groups, and, indeed, after further experiment, may
have to be placed in some other group. The following species have
given interesting results in culture experiments.

Rust of Cocklebur (Puccinia xanthii Schw.).

Observations and culture experiments of the writer show that the
rust of cocklebur is probably limited to one host and is distinct from
the species on Ambrosia, and also justify the suspicion that it lies very
near the border of the Lepto-uredinea\ and may belong to another
group.

On March 1, 1897, the first water-drop culture made gave an excel-
lent germination in forty-eight hours. Long promycelia were pro-
duced, but no sporidiola. On February 13, 1897, at Washington,
D. C, inoculations were made on seedlings of cocklebur and Ambrosia
trifida, resulting in an infection of the former in eighteen days, but
not of the latter. On March 12 a second experiment resulted in a
large number of infections of cocklebur seedlings in fourteen days.
In all these cases spermogonia preceded the teleutospores in the
infected spots. On October 8 of the same year an a"cidium was found
on cocklebur in considerable abundance, associated with the teleuto-
sori, at Perkins, Okla. An inoculation on cocklebur seedlings, made
at Lincoln, Nebr., on February 16, 1898, resulted in the production
of spermogonia in ten da}^. The inoculating material had been col-
lected in October, 1897. An ascidium on cocklebur was again found
in abundance at Las Cruces, N. Mex., on July 11, 1899. Attempts
should be made to infect the cocklebur with this secidium. Doctor
Farlow says an secidium on Xanthium in Massachusetts is frequently
followed by Puccinia xanthii.a

The ease with which artificial infections are made with this rust is
at first surprising. So long as there is warmth and moisture, germina-
tion occurs under almost any condition and at any time.

Rust of Velvet Leaf (Puccinia heterospora B. and C).

In the last-mentioned experiments the inoculating material was
taken each time from dead leaves. The same was true in one experi-
ment with the rust of velvet leaf, November 11, 1896, at Manhattan,
Kans., in which seedlings of the host were infected in twelve days.
For all these experiments the average time of incubation was about
twelve days. In December, 1896, the infected plants of the last
experiment were transferred from Manhattan to Washington, D. C,
and material from these was used to inoculate new seedlings, which
resulted in an infection in nine days. It appears, therefore, that the

"Proc. Amer. Acad. Arts and Sci., Vol. XVIII, p. 75.

PERENNIAL SPECIES. 27

incubation period is shorter if inoculating material is taken from liv-
ing plants, and during- the summer it is probably about the same as
that of infections from uredospores.

Numerous experiments were also made with other lepto species,
including Puccirda grindelise,, Pk., P. variolans, Hark., P. lygodesmise,
E. and E., and P. sherardiana, Korn, with results similar to those
above mentioned. The writer has already called attention to the
phenomenon of the formation of catenulate sporidiola in two of these
species. P. grindelise, and P. variolans.0

PERENNIAL SPECIES.

The chance for the continued existence of a rust through winter
resistance of the uredo without the intervention of another stage has
been discussed. Though such a condition can only exist on a peren-
nial host, or at least one that lives over winter, it must not be sup-
posed that the fungus itself is necessarily or even usually perennial.
As fast as the leaves of the host die the spores simply drop on to the
next lower and younger leaves and produce reinfection, the mycelium
not extending through the base of the infected leaf into the next
leaves. If? however, the mycelium is found within the rootstock and
after a dormant period during midwinter follows the new shoots
upward in early spring and again produces sori at the surface of the
plant, the rust is a true perennial. This condition appears to exist in
tin1 following species.

iEciDIUM TUBERCULATUM E. AND K.

It is now usually supposed that all secidial forms will likely be found
to be connected with other stages, though there are probably more of
these forms whose connections are at present undetermined than there
are of Lepto-uredinese. If any .Ecidium is more likely than another
to be an independent species, certainly the probabilities are largely in
favor of this species, which occurs on Callirrhoe involucrataf for there1
is no need of another stage to perpetuate it, though another host
might give it a wider distribution.

The striking orange-yellow color, large and otherwise conspicuous
sori, and its complete attack of every portion of the host make this an
unusually unique and attractive species (PI. I, frontispiece). A note con-
cerning the hardiness of this species was published by the writer sev-
eral years ago/' The words are here quoted: "^Hkidium tuberculatum

«Bot. Gaz., Vol. XVII r, pp. 455-456.

^Though not previously reported, this rust was found also on Callirrhoi alaeoides
at Sal in a, Kans., in May, L893.
< Hot. Gaz., Vol. XVIII, p. U>.">.

28 INVESTIGATIONS OF RUSTS.

E. unci K. is still producing secidiospores on ( allirrhoe invohtcrata out-
doors here at Manhattan at the time of this writing (October 15, 1893),
and Mr. E. Bartholomew, of Rooks County, Kans., tells me that he has
seen in I >ecember secidiospores on specimens of this host growing close
by a large snowdrift. In the spring secidiospores of this species begin
forming about the first day of. April." On December 20, 1893, after
the above was transmitted for publication, the rust was found still alive
although it had been under 1 inches of snow. In a water-drop cul-
ture of some of the material four spores germinated in twenty-four
hours. Since that time, at later dates in the winter the living rust has
been found, but close within the rootstock, with a faint color still,
but producing no spores. The peculiar manner of growth of the rust,
permeating the entire host and producing scattering sori all along
the stems to their bases, as well as on the leaves, and the difficulty of
germinating the spores harmonize also with the idea of a propagation
by perennial mycelium. Besides the above instance other cultures of
the spores were made as follows: At Manhattan, Kans., May 20, 1893,
spores from Calliivfhoe alca&oides, only a few germinations in forty-
eight hours; at Manhattan, June 9, 1893, spores from G. involucrato,
germinated sparingly in twenty-five hours; at Manhattan, January 30,
1891, spores from ('. invokecrata growing in greenhouse, fair germi-
nation in sixty hours.

In the winter of 1896-97 infected plants of 0. involuorata were
obtained from Kansas and grown in a greenhouse at Washington,
D. C, and on March IT, 1897, inoculations of seedlings of the follow-
ing grasses with spores from these plants failed to produce infections:
Agropyron occidentale, A. richardsoni, Sitanion elymoides, Ely /mis
canadensis, and Bouteloua racemosa.

Rust of Peucedanum Fcenictjlaceum.

An .Ecidium occurs on this host in Kansas and Nebraska which has
been reported as ./:'. anisotomes Reich., but the identity of which is
not yet determined" satisfactorily to the writer. At certain places a
Puccinia follows the iEcidium so closely that their connection is very
probable. Both forms are particularly abundant at Manhattan, Kans.
On April 25, 1893, at that place, it was determined by the study of
many cross sections of the host plant that the mycelium of the ^Ecid-
ium extends into the rootstock. It is one of the earliest rusts in the
spring to appear in that locality. These facts make it probable that
this rust is also perennial. On the other hand, it is possible that the
teleutospores of the Puccinia may produce a very earl}T infection at
the base of the young shoots, resulting in the iEcidium, although in
some localities no Puccinia has yet been found following the JEcidium.

«The species is probably Puccinia jonesii I'k., with the seeidial stage present.

RUST OF PEUGEDANUM F03NICULACEUM. 29

At Lincoln, Nebr., on March 24, 1898, teleutospores of this same Puc-
cinia germinated in a water-drop culture in twenty-four hours.

It .should be noted that it is possible for a perennial rust to exist in
an annual host, the mycelium of the rust being carried over winter in
the seed of the host. Such an instance is practically certain in the
Euphorbia rust already discussed. Granting- that Doctor Eriksson's
experiments were accurate, there would be another example in Pug-
c't n hi glumarum Eriks. and Henn. on wheat.

PLATES.

31

DESCRIPTION OF PLATE?.

Plate I. Frontispiece. A. perennial rust. JEcidium tuberculatum E. and K. on Cal-
lirrhoi involucrata < rr.

Plate II. Fig. 1. — Seedling of Euphorbia dentata grown constantly under bell jar
from rusted seed. Fig. 2. — Puccinia renin* Farl. on Bouteloua racemosa, both
uredosori and ampbtisori being shown. (Natural size.) Fig. 3. — The same ure-
dosori and amphisori shown in fig. 2 magnified 10 diameters. Fig. 4. — Uredo-
spores of Puccinia vexans X 600. Fig. 5. -Aniphispores of Puccinia vexans X 600.
Fig. 6. — Teleutospore of Puccinia vexans X 600. Fig. 7. — Germinating uredo-
spore of Puccinia reruns >; 300. Fig. 8. — Germinating amphispores of Puccinia
vexans X 300. Fig. 9. — Uredosori of Puccinia vexans on young seedling leaf of
Boutilmni racemosa produced by artificial infection with uredospores from the
same host. I Natural size).

32

o

jt. 63, Bureau of Plant Industry, U. S Dept. of Agriculture

Plate

Rusts of Euphorbia and Grama Grass.

i E Mr '08

0 002 813 124 0

ls3Sm