Blasdale: Uredinales of California 105 



hyphae. They have a hyaline epispore and a number of germ pores 

 but rapidly lose their ability to germinate. 



Urediniospores designated by the symbol II, are usually produced 

 in subepidermal sori and ultimately burst through the epidermis as 

 light brown or yellow pulverulent masses. They are produced singly 

 at the ends of hyphae, are always one-celled, either globose, elliptical 

 or pyriform, possess several germ pores and are either echinulate or 

 tuberculate. 



Teliospores, designated by the symbol III, are formed like the 

 urediniospores, but sometimes appear singly, either in or on the tissues 

 of the host. They usually possess a definite pedicel and may be 

 fascicled or compacted into a crust or a cylindrical column. Each 

 spore may consist of a single cell or of as many as twenty cells; 

 each cell usually possesses a single germ pore. They possess a thick 

 epispore, which is dark brown or black in color. On germination 

 they produce a thick promycelial tube, which ultimately produces four 

 cells, each of which develops a single basidia and sporidium. "When 

 the sporidia germinate they produce short tubes which are able to 

 penetrate the tissues of the proper host plant. The formation of 

 basidia is one of the most distinguishing characteristics of the group. 



Many species show well characterized alternation of generations 

 on host plants belonging to the same species (autoecious) or on host 

 plants belonging to different species (heteroecious). 



VI. LIST OF SPECIES 



The genera are arranged alphabetically, and the species numbered 

 consecutively throughout the paper. 



AECIDIUM 



Under this form genus are grouped those aecial forms which have 

 a true peridium and for which no other stage has as yet been recog- 

 nized. 



L Aecidium Collinsiae Ell. and Ev. 



Bull. Washb. Lab., vol. 1, p. 4, 1884. 

 On Cottinsia bicolor Benth., Berkeley and Ukiah. 



2. Aecidium Graebnerianum Hennings 



Hedwigia, vol. 37, p. 273, 1898. 



On Habenaria dilatata (Pursh.) Hook., Death Valley (Coville) ; 

 on H. leucostachys Wats., Mount Eddy (Copeland). 



