CRYPTOGAMS 



361 



employed in producing conidia, which are abstricted by a process of 

 budding from the extremities of hyphal branches. In Protomyces the 

 chlamydospores form an ascus-like sporangium on germination ; in the 

 Smut Fungi, on the other hand, they give rise to a basidium-like conidio- 

 phore. The brand spores are resting spores, they are scattered by 

 the wind, and germinate only after an interval of rest, producing 

 conidiophores in the succeeding spring, the formation of which is 

 characteristically different in the two families of the Brand Fungi, the 

 Ustilcujinaceae and the Tilletiaceae. 



Of the Xlstilaginaceae, the most important genus is Ustilago. U. segetum ( = U. 

 Carlo) causes the mildew and blasting of the inflorescence of Oats, Barley, 

 Wheat. The mycelium pene- 

 trates the ovary enclosed by 

 the palese, and forms dark- 

 brown dust - like masses of 

 escaping brand spores in the 

 place of the seeds. V. Maydis 

 produces on the stalks, leaves 

 and inflorescences of the Maize 

 tumour - like swellings filled 

 with brand spores in the form 

 of a black powder. Other 

 species live on the leaves of 

 . different grasses ; while U. 

 violacea (= XI. anther arum) 

 occurs in the anthers of vari- 

 ous Carophyllaceae {e.g. 

 Lychnis), and fills the pollen- 

 sacs with brand spores. 



The brand spores of Usti- 

 lago fall to the ground, and 

 after a period of rest give rise, 

 on germinating, to a short tube 

 which becomes septated by 

 three or four transverse walls (Fig. 284, B), and functioning as a eonidiophore, pro- 

 duces egg-shaped conidia, both laterally from the upper ends of the intermediate 

 cells, and also from the tips of the terminal cell. When abundantly supplied 

 with nourishment, and also on cultivation in a nutrient solution, conidia are con- 

 tinuously abstricted in large numbers (Fig. 284, C), and then multiply further by 

 budding in the manner of yeast cells (C, D). After the food-supply of the sub- 

 stratum is exhausted, the conidia grow out into mycelial hyphee. The germina- 

 tion of the conidia in the damp manured soil of the grain fields is accomplished 

 during a saprophytic mode of existence, but the hyphal filaments which are 

 eventually produced become parasitic, and penetrate the young seedlings as far 

 as the vegetative cone, where the inflorescence takes its origin. Then the 

 mycelium continues its development, and ultimately terminates its existence by 

 the production of brand spores. No conidia are formed on the host-plant itself. 



The life-history of the Tilletiaceae is similar to that of the Ustilaginaceae. The 

 best known species are Tilletia Tritici ( = T. Caries) and Tilletia laevis, the Fungi 



Fig. 284. — A, Ustilago olivacea. Mycelial hypha in process of 

 forming brand spores (x 400). B-D, Ustilago segetum: JJ, 

 germinating brand spore ; cl, cultivated in nutrient solu- 

 tion (X450); t, transversely septate conidiophores with 

 lateral and terminal conidia (c) : C, germinating brand spore 

 lying in the nutrient solution surrounded by abstricted 

 conidia, which are multiplying by budding (X200) : D, an 

 aggregation of budding conidia ( X 350). (After Brefeld, 

 from v. Tavel.) 



