6 BOTANICAL GAZETTE [july 



Material and methods 



The aecidia included in this study were collected during the 

 spring and summer of 191 2 in the vicinity of New York City and 

 at Woods Hole, Massachusetts. Some 20 different species of aecidia 

 were fixed and examined, and the most favorable were selected for 

 a more detailed study. 



The 6 species treated here are Puccinia Claytoniata Peck on 

 Claytonia virginica, P. Violae (Schum.) DC. on Viola papilionacea, 

 P. Hydrocotyles (Link) Cke. on Hydrocotyle umbellata, P. Eatoniae 

 Arthur on Ranunculus abortivus, P. angustata Peck on Lycopus 

 virginicus, and Uromyces Caladii Farlow on Arisaema triphyllum. 

 I am indebted to Dr. J. C. Arthur for the identification of the 

 aecidia. 



Some of these species have been previously studied from the 

 standpoint of sexuality. The aecidium of Ur. Caladii has been 



studied by Richards (27) and by Christman (9). Richards has 



also studied an aecidium on Ranunculus that probably belongs to 

 the same species as the one studied here. So far as I have ascer- 

 tained, the remaining forms have not previously been studied 

 cytologically. 



Three of these rusts, P. Violae, P. Hydrocotyles, and Ur. Caladii, 

 are eu-autoecious forms, that is, all four spore forms are included 

 in the life cycle and all are borne upon the same host. Two of the 

 other species, P. Eatoniae and P. angustata, are eu-heteroecious 

 forms, the former with the uredosori and teleutosori on a grass, 

 Spheno polis (Eatonia), and the latter with these sori on a sedge, 

 Scirpus. The remaining species, P. Claytoniata, is autoecious, but 

 lacks the uredo stage. It belongs to the opsis group of Schroeter's 

 classification and to the genus Allodus of Arthur's (i). 



In 3 of the species the aecidia are borne on a mycelium that is 

 diffused throughout the tissues of the host. In the other 3 the 

 mycelium is localized within a rather restricted area. These two 

 types of aecidia can usually be distinguished at a glance. The 

 aecidia from a diffused mycelium are distributed uniformly over the 

 leaf or stem surface at approximately equal distances apart, and 

 all on one part of the host are usually at the same stage of develop- 

 ment. When the mycelium is localized, the aecidia are crowded 



