104 University of California Publications in Botany [VOL. 7 



IV. ACKNOWLEDGMENTS 



The completeness of the survey of the rust flora of California here 

 presented is in a large measure due to the assistance of the collectors 

 whose names have been cited, who have furnished specimens or have 

 given additional data regarding them. Especial obligations are due 

 Mr. Ellsworth Bethel for a large amount of information regarding the 

 heteroecious species, and for extended collections of grass and sedge 

 inhabiting species from the southern part of the state both of which are 

 poorly represented in most of the collections which have been made 

 up to the present time. I desire also to express my thanks to Pro- 

 fessor J. C. Arthur, who read over the entire list of species here 

 presented and made many valuable suggestions. It will also be 

 obvious that much help has been derived from such portions of 

 Arthur's arrangement of the North American species of Uredinales 

 (North American Flora, vol. 7) as have been published, of the critical 

 work of Holway in that portion of his North- American Uredineae 

 which has been published, and Jackson's Uredinales of Oregon, pub- 

 lished in the Memoirs of the Brooklyn Botanic Garden. 



V. GENERAL FEATURES OF THE UREDINALES 



The Uredinales represent a group of fungi whose vegetative parts 

 consist of a much branched and septate mycelium, which develops in 

 the leaves, branches, and fruits of certain seed producing plants and 

 ferns and abstracts nourishment from the cells of the surrounding 

 tissues by means of haustoria. The reproductive parts are represented 

 by five different types of spores, one or more of which are frequently 

 lacking and which differ greatly as to form and size as well in the 

 mode of production and germination. The different spore forms are 

 the following: 



Spermatia, designated by the symbol 0, are produced in sub- 

 globose or flask-shaped spermogonia and are minute hyaline bodies, 

 which can be made to germinate but do not appear to perform any 

 important function in the life history. They usually appear with 

 or slightly before the aecia. 



Aeciospores, designated by the symbol I, are produced in cup- 

 shaped or cylindrical aecia, which have a more or less well developed 

 peridium, or in masses, frequently surrounded by paraphyses, in 

 which a peridium is lacking. They are always one-celled and are 

 formed by the successive abstriction of the ends of closely packed 



