296 



U.STILAlilXKAK. 



celia, may develop to mycelia; coalescence of conidia is unknown. 

 In nutritive solutions conidia are formed in large numbers^ and 

 multiply yeast-like till nutriment fails. 



Ust. succisae Magn. 1 frequents the anthers of Scabio* /S'///, 

 ;uid forms pure white spores, easily distinguished from iho.se 

 "f the two preceding species. The anthers appear to lie thickly 

 covered with glassy granules. The spores produce four-Mled 

 promycelia from which conidia are formed. (Britain. ) 



Ust. tragopogonis (Pers.) (Britain). 

 This fungus forms its spores in flowers 

 of species of T/v///o/^//o//, and in many 

 localities has a wide distribution. 

 The development of the flower is 

 retarded, so that it retains externally 

 the appearance of a flower-bud en- 

 closed in its bracts (Fig. 161). The 

 dark- brown or violet spores escape 

 through intervals between the bracts-; 

 they are 13-17/x long, 10-1.5//. broad, 

 with reticulate markings on their 

 coats. They easily produce in water 

 four or five- celled promycelia from 

 which conidia are given off, often 

 followed by coalescence. In nutritive 

 solutions development is much more 

 vigorous, secondary conidia may he 

 produced, and coalescence always takes place. 



Ust. scorzonerae (Alb. et Schwein.) is at first sight very 

 similar to Ust. tragopogonis. Its spores are found in flowers 

 of Scorzonera humilis, Sc. purpurca, and cultivated species, <:</. 

 Sc. hispanica ; while its mycelium hibernates in the perennial 

 root-stocks of these. The spores are produced rapidly and 

 in large numbers ; they germinate easily in water, forming a 

 four-celled promycelium, and thereafter conidia which do not 

 pair. 



Ust. cardui Fisch. v. Waldh. (Britain). This is the cause 

 of a stunting of the flower-heads of Carduus acanthoides, C. 

 nutans, and ,SV///A///// M)-i<t/iimi, while at the same time they 

 become filled with a brownish-violet spore-powder. The spores 



1 Magnus, Hedu'iyia, 1875. 



FK.. lii - 2. Ustilago tragopogonis. 

 Development of spores: successive 

 stages of development, in order of 

 the letters, a, Sporogenous branch, 

 just appearing on the surface of 

 young corolla of Tmgopotion pra- 



is, and beginning to form a tuft 

 ' ! 1 iraiichlets. b and c, Formation of 

 spores from the mycelium, d, Spore- 

 flump with several ripe spores, the 

 episporium of which is coloured 

 dark-violet and thickened in a 

 reticulate manner, (x 300). (After 

 De Bary.) 



