IIKMII'.ASIDIOMVCETES 371 



means of conidia produced on the external portion of the host, as 

 in Entyloma, and typically by means of chlamydospores formed 

 within interstitial or terminal cells or hyphae. Chlamydospores are 

 for the most part dark colored, simple or agglutinated, and with or 

 without sterile appendage cells. The chlamydospores produce upon 

 germination a basidium-like structure known as a promycelium, 

 which in turn originates lateral or terminal sporidia. In this order 

 the fusion of sporidia, or of germ tubes from these, is common. 

 This cell fusion is not accompanied by nuclear fusion. Each 

 sporidium is provided with a single nucleus. 



This order is divided into two families, Ustilaginaceae and 

 Tilletiaceae, based upon characters which become evident only in 

 germination. The characters are therefore largely those of the 

 germ tube or promycelium. 



Ustilaginaceae. Spore masses are made up of simple or com- 

 pound spores. The promycelium is usually divided into two or 

 four cells, originating both lateral and terminal sporidia, which 

 sporidia, in saccharine or other nutrient solutions, are for the most 

 part able to bud after the fashion of yeast fungi for an almost 

 indefinite period of time. This family includes from seven to 

 eleven genera, according to different authorities. 



The characters of only three genera need to be considered in 

 order to become familiar with the basis of classification. 



1. Spores single, spore masses dusty at maturity and without any sort of 



inclosing membrane Ustilago 



2. Spores agglutinated in balls, spore masses more or less dusty. Spore 



balls usually evanescent, spores very dark Sorosporiiun 



3. Spores agglutinated in balls, spore masses more or less dusty. Spore 



balls rather permanent, spores now adhering by folds or thickenings 

 of the outer coat Tolyposporium 



Tilletiaceae. Spore masses are made up of simple or compound 

 spores ; these masses dusty and exposed, or imbedded in the tis- 

 sues. The promycelium is short, originating usually an apical clys- 

 ter of more or less filiform sporidia. The latter may fuse in pairs, 

 and whether fusing or not, may produce secondary conidia, or may 

 germinate directly into infection hyphae. 



This family includes from eight to ten groups of generic rank, 

 the differentiated characters of three- of which mav be indicated. 



