DEVELOPMENT OF PLANTS 



261 



down into this cavity in regular lines, forming the radiating 

 plates or gills noted in Fig. 170. This development divides the 

 ball of hyphae into an upper part or pileus and a basal region, 

 the stalk or stipe. As this growth proceeds the mass of hyphae 

 extending from the margin of the pileus to the stipe becomes 



P 



FIG. 170. Habit of a poisonous mushroom, Amanita: A, the mature 

 mushroom s, stipe; p, pileus; g, gills; a, annulus; v, volva, a part of which 

 appears in patches on the top of the pileus. C, young form of the Amanita, 

 the volva beginning to break. D, later development, the volva completely 

 ruptured, disclosing the pileus, stipe and velum, vl. H. O. Hanson. 



drawn out and ultimately forms a rather thin membrane known 

 as the velum (Fig. 169, 2, vl). This entire growth is often 

 enveloped by a sheath-like mass of hyphae, the volva (Fig. 170, 

 C, D). At this stage of development, the young mushroom is 



