684 



THE SUBDIVISIONS OF THE VEGETABLE KINGDOM. 



way groups of cells may hang together in chains (fig. 387^) for a short time, but 

 they disarticulate sooner or later. As the substratum becomes exhausted the cells 

 exhibit a tendency to form spores in their interior (2-8), the cell being as it were 

 transformed into an ascus (fig. 387'''). The special physiological activity associated 

 with this and several other species is alcoholic fermentation {cf. vol. i. p. 506), i.e. 

 the splitting up of sugar into alcohol and carbonic acid. 8. cerevisece is used in 

 brewing, S. ellipsoideus causes the fermentation in the juice of the Grape. 

 S. mycodemia forms a scum on wine and beer, and is of 

 interest in that it produces mycelial tubes. 



In all there are some 40 species of Saccharomyces. 



Alliance XIX. — Basidiomycetes. 



Parasites and saprophytes, reproducing by means of conidia 

 which arise on basidia in definite number. Besides these 

 characteristic conidia there are subordinate fructifications. 



Families: Uredinece, Auriculariaceoß, Treinellacem, Pilacracece, 

 Dacromycetes, Hymenomycetes, Gasteromycetes. 



The Basidiomycetes are an exceedingly large alliance, and 

 include forms from the simplest to the most complex. They 

 all agree, however, in the production of conidia from a definite 

 hasidiurti, a character which gives its name to the group. As 

 has been already pointed out (p. 674) there are two families 

 in the Hemibasidii, i.e. the Ustilaginacese and the Tilletiacege. 

 In both families a promycelium or basidium arises from the 

 chlanty dospore ; in the former it is septate and conidia are cut 

 off laterally, in the latter it is non-septate and the conidia are 

 produced in a tuft at the extremity. In the Uredinese a 

 basidium arises from each cell of the teleutospore (the probable 

 equivalent of a chlamydospore), and this basidium is trans- 

 versely septate, four cells being cut ofi' at the end of the tube away from the spore. 

 Each of these cells produces a little process, and from each process a conidium is 

 abstricted. In all the other families of Basidiomycetes the teleutospore (or chlamy- 

 dospore) is suppressed, and the basidia are directly continuous with the hyphae of 

 the Fungus. Otherwise, the basidia of Auriculariaceae, Tremellacese, and Pilacracese, 

 all belong to the type of the Uredinese, and are derivable from the Ustilago-iorm. 

 On the other hand, the basidia of Hymenomycetes and Gasteromycetes, and 

 probably also of Dacromycetes, belong to the Tilletia type {cf. p. 675). The conidia 

 do not arise laterally, but from four processes at the tip of an unsegmented basidium 

 (see figs. 389^ and 390^). The very general restriction of the number of processes 

 arising on the basidium to four is without doubt a feature of some importance, and 



Fig. 389. 



1 Portion of a lamella of an 

 Agarieus with a basidial 

 layer (from which conidia 

 are being budded off) 

 on eitlier side. - Shows 

 three basidia, more high- 

 ly magnified, from the 

 basidial layer of the same 

 fungus; conidia are being 

 abstricted from the four 

 processes (sterigmata). 

 1x200; 2x500. 



