THE FUNGI WHICH CAUSE PLANT DISEASE 327 



O. Pycnia or pycnial stage 



I. .Ecia or tecial stage 



II. Uredinia or uredinia stage 



III. Telia or telial stage 



The spores in all cases, except those of the basidiospores and 



Fig. 241. — Amphispores, urediuiospores and teliospores of Puccinia vexans. 

 After Holway. 



pycniospores arise by direct conversion of a mycelial cell into 

 a spore, i. e., they are chlamydospores. 



Mesospore is a term applied to occasional unicellular forms of 

 teliospores found in Puccinia and related genera which do not 

 usually have unicellular teliospores. 



As has been said the pycniospores seem to be functionless 

 though by some it is thought that they do function but that man 

 has yet failed to find the conditions under which they readily 

 germinate and cause infection. The secial stage appearing first, 

 and thus commonly in the spring, is often called the "spring stage." 



