328 THE FUNGI WHICH CAUSE PLANT DISEASE 



It serves as an early stage to propagate and spread the fungus. 

 The uredinia often called the "summer stage" constitute the 

 phase usually of longest duration and of most injury. Its function 

 is preeminently to multiply and spread the fungus. 



The teUa, often called the "winter stage," usually, but not al- 

 ways, constitute the resting, hibernating stage. In many instances 

 the teliospores must rest over winter before they are capable of 

 germination. Classification is based primarily on the teUospores. 



While all five of the spore forms discussed above are typical of 

 many species there are many other species which do not possess 

 all of these forms or indeed which may possess only one spore form. 



Schroter for convenience groups the rusts, according to the 

 spore forms that they show, under the following type names 

 though it must be recognized that such grouping is purely arti- 

 ficial and does not necessarily bring together closely related species. 



Eu-type 0, I, II, III present; 



Brachy-type 0, II, III present; I omitted. 



Opsis-tjrpe 0, I, III present; II omitted. 



Hemi-type II, III present; 0, I omitted. 



Micro-type only III present; germination only after 



a resting period. 

 Lepto-type only III present; germination without a 



resting period. 



As examples of the above we have the following: 

 Eu-type, Puccinia asparagi, 0, 1, II, and III, all on Aspar- 



agus. 

 Brachy-type, Puccinia suaveolens, 0, II, and III, all on thistle. 

 Opsis-type, Puccinia tragopogonis, 0, 1, and III, all on salsify. 

 Hemi-type, Uromyces caryophyl- 



hnus, II, and III, both on Di- 



anthus. 

 Micro-type, Puccinia ribis, HI, on Ribes. 



Lepto-type, Puccinia malvacea- 



rum, III,onhollyhock. 



Hundreds of the hemi-types will doubtless be revealed by study 

 to be hetercDcious eu-types. 



