68 British U7''edine(X and Ustilaginecr. 



nected with the remains of the spore-forming hyphae. At 

 maturity these spores do not break up into dusty masses 

 like Ustilago, but remain as compact colonies embedded in 

 the tissues of the host-plant. Each spore has two coats^ 

 and contains coarse protoplasm. The outer coat is some- 

 times gelatinous at its maturity. 



Urocystis.—T\\Q process has been studied by Klihn,* 

 De Bary,t Wolff,| and Winter §. The spore-forming 

 hyphae become swollen at their ends ; two or more of these 

 branch and wind themselves together, generally in a spiral 

 manner, so as to form a glomerulus, and then, becoming 

 highly gelatinized, they are quite indistinguishable from 

 each other. In U. occulta, Wolff considers that they have 

 a common investing membrane. At the same time, other 

 branches are given off from the spore-forming hyphae, 

 which apply themselves to the outside of the glomerulus 

 (Plate V. Figs. 13, 14, 15). As Winter points out, this 

 might be looked upon as a sexual act, the central spiral 

 branches of the glomerulus being the carpogonium, and the 

 external enveloping branches the pollinodium ; but there 

 is no proof that this is really a sexual act, especially as 

 similar conditions occur in the spore-formation of various 

 Ustilaginese, and in Geminella, in which no sexuality 

 occurs. The spores are formed entirely from the gelatinized 

 central glomerulus, and, as De Bary first showed, the pseudo- 

 spores are formed by the outer branches. Prillieux || con- 

 siders that the spores of Urocystis are formed in a similar 

 manner to those of Sorosporium. The details of his obser- 

 vations are given on the plate which accompanies his paper. 



* Kiihn, loc. cit., pp. 78, 79. 

 t De Bary, " Morph. und Physiol.," p. 125. 

 X Wolff, Bot. Zcitiiug, 1873 ; " Der Brand des Getreides," 1874. 

 § Winter, Flora, 1S76, " Ustilagineen." 



II Prillieux, "Sur la formation et la germination des Spores des Urocystis," 

 Ann. des Sricncc Nat., 6*" sen, Bot., vol. x. pi. i. 



