No. 5.] USTILAGINE^ OF CONNECTICUT. 13 



III. Spores in more or less permanent balls. 



A. Forming a dusty or granular sorus at maturity. 



1. Spore balls consisting only of spores. 



a. Often evanescent (Ustilago-like spores) . . . 



Sorosporium. 



b. Quite permanent, adhering by folds of spore 



coats Tolyposporiiim. 



2. Spore balls with a cortex of sterile cells 



Urocystis. 



B. Permanently embedded in the plant tissues. 



1. Spore balls with a definite cortex of sterile cells 



Doassansia. 



2. Spore balls without cortex but with sterile 



threads in center Tracya. 



USTILAGINACEiE Schrot. 



The sori usually form exposed, dusty, or agglutinated 

 spore masses. Germination is by means of a septate pro- 

 mycelium, which usually gives rise to terminal and lateral 

 sporidia (capable of yeast-like multiplication in nutrient solu- 

 tions), or else to infection threads. Figs. 21, 23-25. 



Ustilago Rouss. 



The sori occur on various parts of the host, according to 

 the species,' and at maturity form dusty, usually dark colored 

 spore masses. The spores are single, separate, of small to 

 medium size (5-18^), and are produced irregularly in fertile 

 threads that entirely disappear through gelatinization at ma- 

 turity. Figs. 1-4, 43-55- 



This is the most common and the typical genus of the 

 smuts. Saccardo, in his Sylloge Fungorum, describes about 

 250 species for the world: 72 species occur in North America 

 and 18 in Connecticut. A number of the species possess eco- 

 nomic importance as parasites of the cereals. 



Key to Species of Ustilago. 

 I. Spores olive or reddish brown. 

 A. Spores smooth. 



1. Sori in leaves forming linear striae 



U. longissima. 



