402 



BOTANY 



PAKT II 



spores at the summit ; these may be sessile or situated on sterigmata 

 (Figs. 333, 343). 



The Ustilagineae are of interest since in one family of these 

 fungi the basidia are divided, while in the other they are undivided. 

 The number of spores produced is not a definite one but often very 

 large. 



The basidia may be regarded as a special form of conidiopliore, since it is usual 

 to give the name conidia to spores arising in the fungi by budding from a cell. 



In addition to conidiophores ditferentiated as basidia, the Basidiomycetes 

 produce other forms of conidia as accessory fructifications in many species. The 

 origin of asexual spores by the rounding off of hyphal cells and their developing 



Fio. 333. — ArmiUnriamellea. .4,ymmg 

 basidinm with the two primary 

 miclei ; B, after fusion of the two 

 nueloi. Hypliolmna (ippendiculalum, 

 C, a basidinm before the four nuclei 

 derived from the secondary nucleus 

 of the basidium have passed into the 

 four basidiospores ; D, passage of a 

 nucleus through the sterigma into 

 thebasidiospore. (After Ruhland.) 



Fin. 334. — Basidia. A, of a Uredineons 

 fungus (En.dnphyllum Enphorhiae silva- 

 ticae) (after Tui.asne). B, Of one of the 

 Tremellineae (Trcmella hitesccns) (after 

 Brefeld). (x 450. From v. Tavel, 

 I'ilze.) 



a thick wall and ultimate separation, is different from that of conidia (clilaniydo 

 spores according to Brefeld). These appear in the Ustilagineae as the smut- 

 spores, and as tlie rust-spores in the Uredineae. In these groups the basidia 

 arise directly from spores of this kind (Figs. 334, A, 336). In other Basidio- 

 mycetes, if a few simple forms are disregarded, the basidia are always borne upon 

 or within more or less complicated fructifications. The layer in which the 

 basidia are associated together is termed tlie hymenium. These fructifications 

 correspond to those of the Ascomycetes, but no sexual process is concerned in their 



Order 1. Ustilagineae (Smut-Fungi) (*•'"') 



The Ustilagineae are parasites, and their mycelium is found ramifying in higher 

 plants, usually in definite organs, either in the leaves and stems, or in the fruit or 

 stamens. Tlie Gramineae in particular serve as host ])lants ; certain sjiecics of 



