HEMIBASIDIOMYCETES 319 



In other instances infection occurs in the flower, the 

 spores being deposited by some agent on the stigma, and 

 a mycelium is formed in the ovary. The mycelium is 

 very delicate, septate, widely diffused in the tissues of the 

 host, mostly intercellular. Haustoria are produced by 

 some species. The resting-spores teleutospores of some 

 are either formed from the ordinary mycelium or from 

 specialised branches, and are either naked as in Ustilago, 

 or contained in a special receptacle as in Sphacelotheca. In 

 the genus Entyloma spores are formed on all parts of the 

 mycelium, their first indication being the appearance of 

 spherical swellings which continue to increase for some time, 

 and may be either terminal or intercalary. From the proto- 

 plasm in these swellings the spores are formed, and form 

 their own cell-wall while yet enclosed in the wall of the hypha. 

 The wall of the hypha forms a gelatinous outer coating to the 

 spore in some species. In Ustilago the spores are formed 

 on special branches or sporogenous hyphae, which are very 

 much branched and produced in great numbers at definite 

 points in the tissue of the host. These sporogenous hyphae 

 become cut up into isodiametric portions by transverse 

 septa at the same time the wall swells very much, form- 

 ing a gelatinous membrane enclosing the protoplasm, 

 which develops into a spore provided with its own cell- 

 wall, while yet enclosed in the gelatinous wall of the hypha, 

 which eventually disappears, leaving the spores as a dry, 

 dusty mass. In the genera Sorosporium, Tuberrinia, and 

 Urocystis the spores are produced in compact clusters, 

 and surrounded by a special envelope which either soon 

 disappears, or is persistent. In Urocystis this envelope 

 consists of sterile cells. A glimpse of the highly special- 

 ised peridia containing the spores in some forms of the 



