648 



FUNGI 



(Agaricus campestris) may be taken as a type, the receptacle has the 

 form of a cap-shaped pileus (fig. 484), raised on a stalk or stipe, 

 the whole composed of a pseudo-parenchyme consisting of a dense 

 agglomeration of parallel hyphse, the cortical portion of which is 

 slightly differentiated into an epiderm. In the family to which the 

 mushroom belongs, the hymenium is borne at the edge of narrow 

 gill-like projections or lamellc? radiating from the apex of the stipe 

 on the under side of the pileus. Among the basids are seen other 



cells of similar shape and 

 usually larger size, also the 

 extremities of special hyphse, 

 called cystids, the function of 

 which is obscure. The basi- 

 diospores vary greatly in 

 colour in different genera. 

 They are always unicellular, 

 and the membrane consists 

 of two coats, the endospore 

 and exospore, the former of 

 which consists of fungus- 

 cellulose, while the latter is 

 more or less cuticularisecl. 

 On germinating the endo- 

 spore bursts through the 

 exospore, and grows into a 

 germinating filament, from 

 which is developed the my- 

 cele, and on this ultimately 

 the receptacles. 



Lichens, The micro- 

 scopic study of this group 

 has acquired a new interest 

 for the botanist, from the" 

 remarkable discovery an- 

 nounced in its complete 

 form by Schwendener in 

 1869 ] (and now accepted 

 by the highest authorities), 

 that instead of constituting 

 a special type of Thallo- 

 phytes, parallel toAlgce (with 

 which they correspond in 

 their vegetative characters) and Fungi (to which they are more 

 allied in fructification), they are really to be regarded as compo- 

 site structures, having an algal base, on which fungi have sown 

 themselves and live parasitically. As, however, they do not 

 furnish objects of interest to the ordinary microscopist (the 

 peculiar density of their structure rendering a minute examina- 

 tion of it more than ordinarily difficult), nothing more than a 



1 See his memorable work Ueber die Algentypen der Fleclitengonidien (Basel, 

 1869). 



FIG. 484. Agaricus campestris, natural size. 

 (From Goebel's ' Classification and Morpho- 

 logy of Plants.') 



