HETEROECISM ' 



329 



ture 3 days later. After an additional period of 8 to 12 days 

 aeciospores were produced, and a month later urediniospores 

 and teliospores. By sowing aeciospores on other beans, he se- 



FiG. 127. Germination of teliospores. A. Section of sorus of Coleospor- 

 ium sonchi-arvensis. The one-celled teliospores, in situ, become trans- 

 formed into four superimposed cells (the promycelium or basidium), each 

 of which bears a sterigma at whose tip the basidiospore is produced. 

 B. Typical germination of teliospore of Uromyces appendicidatiis. C. Ger- 

 mination of one-celled teliospores in telial column of Cronartiinn quercmim. 

 D. Section of telial sorus of Thekopsora areolata. Stages in germination 

 of teliospores. The promycelium extends to the exterior of the host. 

 (After Sappin-Trouffy.) E. Piiccinia malvacearum; at left, normal germina- 

 tion, in middle, when teliospores are submerged, and at right, when pres- 

 sure of Oo is reduced. (After Sappin-Trouffy.) F. Ravenelia sp. G. Bar- 



clayella sp. 



cured uredinia, followed by telia. Having thus established that 

 the bean-rust fungus is polymorphic, de Bary devoted himself 

 to similar sowings of spores from rust pustules on barberr\^ and 

 on wheat. Again he found that one polymorphic species was in- 

 volved on both hosts, that the different spore forms appeared in 

 sequence, that the aecial and pycnial stages occurred on barberry 



