UREDINALES 585 



In the micro- type (0, III), finally, the life cycle becomes still simpler 

 by the absence of the uredinia. In Puccinia Malvacearum, the basidio- 

 spore develops a uninucleate mycelium which produces the telia where 

 plasmogamy occurs. The fusion cells develop to short, branched, binu- 

 cleate hyphae, each of whch forms a teliospore at its tip. This can 

 germinate immediately to a basidium with basidiospores, which infect 

 new hosts and again develop uninucleate mycelia with telia. In con- 

 trast to the long-cycled forms, this species is able to complete its life 

 cycle several times within one season. These micro- forms, whose telio- 

 spores are capable of immediate germination, are sometimes placed in a 

 special group called lepto- forms. Wintering over occurs by the delayed 

 germination of teliospores. In other micro- forms, as Puccinia Veroni- 

 carum, two types of teliospores are formed (p. 576). The life cycle of 

 the micro- type takes place according to the following scheme (the pycnia 

 which are absent in P. Malvacearum are here added) : 



^jrPycnium— »Pycni<)8pores P C . R 



Uninucleate— »Teliuni— *Sexual cells— »Binucleate— ►Teliospores— »Basidia—»Basidiosporea 

 mycelium mycelium . 



Diagram XXXVI. 



In Uromyces Scillarum, the scheme is modified so that plasmogamy 

 occurs somewhere on the mycelium. This scheme is the same in principle 

 as that assumed for the Septobasidiaceae. Still simpler is Gallowaya 

 pinicola, where the teliospores are not formed as such, but each cell of the 

 short binucleate chain resulting from plasmogamy divides directly 

 after caryogamy to form a phragmobasidium. The vestigial pycnia 

 are the only structures which distinguish it in principle from the simpler 

 Auriculariaceae, since not even a resting organ, such as the probasidium, 

 is formed. 



Vestigial pycnium 



Uninucleate^-»-Telium— >SexuaI cells— >Short chain of->Basidia— ►Basidiospores 

 mycelium binucleate cells 



Diagram XXXVII. 



In these different developmental types, the following courses exist: 

 1. The plasmogamy is shifted in time and place. It occurs in the 

 aecia of the eu-, -opsis and endo- forms (in Uromyces Scrophulariae, also 

 somewhat on the mycelium) before the development of pycnia, in the 

 uredinia of the brachy- forms, and in the telia or somewhere on the 

 mycelium in the micro- forms. Characteristically, it occurs between 

 two slightly differentiated hyphae or hyphal tips, in the former hetero- 

 gamously by the migration of one nucleus to the other cell, in the latter 



