386 



ORGANOGRAPHY. 



guish certain forms of stalked spores which thus arise myce- 

 lium : these conidia may he regarded as a fourth kind of 

 reproductive organ. Their nature is at present hut imperfectly 

 ascertained, they appear physiologically to he analogous to the 

 gonidia of lichens. 



In other Fungi which have naked spores, or exospores as they 

 are sometimes termed, the reproductive apparatus upon which 

 they are placed, is of a much more complex structure. That 

 of the common Mushroom {Agaricus campestris), (Jig. 824), 



Fig. 824. 



Fig. 825. 



Fig. 824. Vertical section of the common Mushroom {Agaricus campestris). 

 my. Mycelium, to/. Remains of volva. s<. Stipe. «?i. Annulus. A. llyme- 



nium with its lamellae, la. p. The pileus Fi'o. »25. Transverse section 



of portion of a lamella of Agaricus. h. Ilymenium. bos. Basidia, each 

 bearing at its apex four spores, spo. a and b. The four spores separated from 

 the basidia. cys. Cystidia or sacs containing granular bodies. 



maybe taken as an example. The fructification is here first de- 

 veloped in a hollow round body, called the volva, which arises 

 from the mycelium, my ; as the fructification becomes matured 

 it breaks through the volva, and the following parts may then 

 be seen, namely, a cap-like body, called the pileus, p, placed on 

 a stalk or stipe, st, and at the base of which are the remains of 

 the volva, vol. On the under surface of the pileus a number of 

 vertical plates or lamina? arc situated, which radiate from the 

 centre towards the circumference, these are the lamella or gills, la ; 

 they constitute collectively tlie hymenium, h, upon which the 

 spores are ai-ranged. The hymenium is at first enclosed in a 

 membrane called the veil or indusium, but this is soon ruptured 

 by the development of the pileus and stipe, and is either com- 

 pletely torn away from the latter, or, as is more commonly the 

 case, it remains as a sort of ring or annulus, an, surrounding the 

 upper part of the stipe. 



The hymenium varies in its character and position in dif- 

 ferent genera. In some it is on the upper surface of the pileus, 

 as in Helvella, instead of on the lower, as in Agaricus. Some- 



