Sforc-fonnation. 1 9 



is much branched, and the spore-forming hyphic become swollen at certain 

 places along their length as well as at their ends. The contents of the cells 

 acquire the characters of spores, so that they are marked oi? or intercalated 

 between certain portions of the hyphtc. In Tilletia the spores are onlv 

 formed at the ends of the branches. In this intercalary formation a series 

 of spores may be seen arranged in regular succession with the intervening 

 remains of the hyphre. When mature, they do not break up into dusty 

 masses, but remain embedded in the tissues of the host-plant. Each matur(^ 

 ■spore possesses two coats, and the outer coat is sometimes gelatinous. 



Urocystis. 



The development of the spores has been studied principally by De Barv, 

 Woli?, and Winter. The spores are produced in compact clusters with a 

 special envelope of sterile cells, and the mode of formation of both these struc- 

 tures has been generally followed. The spore-forming hyphse branch at 

 their free ends, and the first beginning of a cluster is indicated by the branches 

 becoming swollen and curved, and winding themselves round each other 

 generally in a spiral manner, seas to form a glomerulus or ball. 



Their walls become so gelatinized that they run into each other and blend 

 so that they are quite indistinguishable from one another. The spores are 

 formed entirely fro'n these gelatinized central balls and consist of a group of 

 cells firmly bound together. Each cluster of spores is surrounded at an early 

 stage by slender curved branches from the hyphte, and these outer branches 

 closely invest the spores and form the envelope. These investing hyphae, as 

 DeBaryhas shown, divide into short cells by means of transverse septa, and, 

 while most of them disappear as the spores ripen, a number varying with the 

 individual species persist and form the envelope of the mature cluster of spores. 

 The number of spores in a cluster vary and sometimes there is only one sur- 

 rounded by its sterile envelope. 



DOASSANSIA. 



Cornu, who founded the genus, Fisch, and Setchell have studied the de- 

 velopment of the spores. When a sorus is about to be formed, the hyph?e 

 give off numerous interlacing short branches which are soon formed into 

 tangled knots. It is from these knots that the spores are formed. The cells 

 of the hyphfe in the interior of the knots become swollen and form a mass of 

 large, thin-walled, polygonal cells, which become the spores, the process being 

 accompanied by a gelatinization of the walls. The external portion is at first 

 composed of compact layers of almost unaltered hyphte, but shortlv before 

 the ripening of the spores the "cortex" of sterile cells is indicated. These appear 

 just beneatli the reduced layer of investing hypha^ and arc probably formed 

 from a layer of cells similar to and adjoining those from which the spores are 

 formed. The sterile cells gradually become oblong or wedge-shaped, lose their 

 granular contents, and are filled with air. taking on the brown colour of the 

 wall characteristic of maturity. 



