GROUP i. THALLOPHYTA: FUNGI. 



301 



forms a number of reproductive cells, sporidia, of various form ; the 

 sporidia are usually developed on a small promycelium, which may be 

 either multicellular (Fig. 181 A), or unicellular (Fig. 181 B). In most 

 forms these sporidia then coalesce in pairs ; but in any case they germin- 

 ate, either producing at once the mycelium which will bear the resting- 

 spores (e.fj. Protomyces), or a second promycelium bearing secondary 

 sporidia. from which the mycelium bearing resting-spores is developed 

 (e.g. Tilletia Caries). 



In some species (e.g. Entyloma Ranunculi, Tuburc.inia Trientalis) the my- 

 celium, before it produces the resting-spores, developes conidia ; these are 

 small, thin-walled, somewhat spindle-shaped cells, developed by abstric- 

 tion from the ends of unbranched simple conidiophores. 



The sporidia, when cultivated in nutrient solutions, may be made to 

 multiply actively by gemmation, producing a number of yeast-like cells. 



The most important and the inost common species are Ustilago Carbo, 

 which especially attacks Oats, but other Cereals and Grasses as well : U. 

 Maidis, which produces large tumours in the Maize, filled with resting- 

 spores : Urocystis occulta, which fructifies in the leaves and haulms of 

 the Eye : Tilletia Caries, the Smut of Wheat ; this is dangerous because 

 the grains filled with resting-spores remain closed, and are therefore 

 harvested with the sound ones. Many other species and genera infest 

 wild plants. 



Sub-Class VI. BASIDIOMYCETES. This sub-class includes 



a large number of plants, both, saprophytes and parasites, the 



fructifications of 



which are well 



known as Mush- 

 rooms, Toad -stools, 



and Puff-Balls; they 



are the most highly 



organised of the 



Fungi. 



The body is a 



branched septate 



mycelium, growing 

 in the substratum, 

 and bearing the re- 

 productive organs 

 which come to the 

 surface. That of 

 the common edible 

 Mushroom is gener- 

 ally termed " mush- 

 room-spa wn." 



FIG. 182. A Section of young compound sporopbore of 

 Agarieus (Amanita) vaginatui: v the velum universale; 

 st the stipe; h the pileus ; I the lamella: B the same 

 Romewhat older; the velum v is ruptured. C Agarieus 

 nwlleiis: m the mycelium (Rhizomorpha) ; in the smaller 

 specimen to the right the hymenophore is still covered 

 by the velum partiale o ; in the larger specimen the velum 

 is almost completely ruptured, and remains attached to the 

 stipe as the ring, a. (i nat. size.) 



