Seed Carriage of Euphorbia Rusts 137 
EVIDENCE OF THE SEED CARRIAGE OF THE EUPHORBIA RUSTS, 
UROMYCES PROEMINENS AND U. DICTOSPERMA.' 
E. B. MAINS. 
As part of the investigations of the life cycles of rusts being car- 
ried on by this laboratory, two species of Uromyces, U. proéminens 
(DC.) Pass. and U. dictosperma Ellis & Ev., have been studied. U. 
proéminens (U. Euphorbiae Cooke & Pk.) was studied by Carleton,’ 
who showed that this rust was carried by the seed of Huphorbia dentata 
Michx. Arthur’ showed that this species was autoecious by sowing the 
aeciospores from aecia on Huphorbia Preslii Guss. (“E. nutans’), ob- 
taining uredinia and telia on the same host. The writer’s attention 
was attracted to this rust on account of the more or less systemic 
aecia which persist throughout the season, the heavy production of 
aecia, uredinia and telia on the fruit, and the evident strains which 
exist in this rust in the vicinity of Lafayette, Ind. U. dictosperma is 
a species found on Luphorbia Arkansana Eng. & Gr. and other species 
farther west in Nebraska, Kansas, Texas and westward. The life his- 
tory of this species has been in question, first as to whether the sys- 
temic aecia on these hosts belong to this species or to some heteroecious 
species, and second as to whether uredinia are produced in the life cycle. 
Uromyces proéminens. 
In the fall of 1920, seed was collected from plants of Euphorbia 
dentata which were heavily rusted with telia of this rust. In the field 
this species does not appear until midsummer, so that by starting the 
plants in the greenhouse there is no chance for infection from without. 
The seed was planted the 22d of January and about the time the first 
leaves were well developed, sixty of the plants were transplanted to a 
flat. Infection first showed up March 1st, when pyenia appeared upon one 
capsule of one plant. Following this, other plants showed pyenia or 
aecia or both. Since there was some variation in the manner of de- 
velopment on the various infected plants, each will be discussed sepa- 
rately. 
Plant 3-4. 
The rust showed on this plant as pyenia upon one of the terminal 
capsules of the main shoot March Ist. March 27th, two more capsules 
showed pyenia and both pyenia and aecia appeared on the leaves of 
the secondary branches arising from the axils of the cotyledons. May 
4th, aecia also had appeared on the terminal fruits. No further de- 
1 Contribution from the Botanical Department Purdue University Agricultural Ex- 
periment Station. 
2 Carleton, M. A. U.S. Dept. Agri. Bureau Plant Ind. Bull. 63 p. 9-11. 1904. 
3 Arthur, J. C. Bot. Gaz. 29 p. 271. 1900. 
