GROUP I. THALLOPHYTA : FUNGI. 303 



towards the lower surface forming the lamellae. Each lamella 

 (Fig. 183 B) consists of a mass of hyphae, constitxiting the trama ; 

 as the hyphae approach the surface of the lamella, the cells become 

 shorter. The last cells, before reaching the hymenial laj'er, are 

 very short, and constitute a definite layer, known as the sub- 

 hy menial layer (Fig. 183 B, C, sh}. The terminal cells of the 

 hyphae constitute the hymenial layer (Fig. 183 B hy). This con- 

 sists of somewhat elongated club-shaped cells, some of which bear 

 spores, and are termed basidia, whilst the others are sterile, and 

 are termed paraphyses (Fig 183 C q}. Each basidium developes at 

 its apex 2-4 delicate outgrowths, the sterigmata, and at the apex 

 of each sterigma a single small spore (C s' s") is formed. These 

 spores are termed basidiospores, with reference to their mode of 

 origin. 



The form of the compound sporophore, as 

 also the relation of its different parts, varies 

 widely in the orders and families of the sub- 

 class. In some families (e.g., Auricularieae, 

 Tremellineae, Clavariese Hydneae, most 

 Polyporeee, and some Agaricinae), the hymen- 

 ium is exposed from its first development, 

 and the sporophore is consequently said to 

 be gymnocarpous. In Polyporus volvatus, 

 species of Boletus, and in some Agaricinae 

 (e.g. sub-genera Armillaria, Psalliota, of the 

 genus Agaricus, etc.) the hymenium is covered FIQ ]gl _ Multicellular 

 for some time by a membrane, termed a basidium of Tremeiia : 

 velum partiale. as described above (see Fig. 8 sterigma ; p basidio- 



spores. (x 350.) 



182); the sporophore is then termed hemi- 



angiocarpous. Finally, the whole sporophore may be surrounded 

 by a membrane, which is dehiscent or indehiscent, and is then 

 said to be angiocarpous. This is due to the fact that the sporo- 

 phore is developed from the internal portion of the primitive mass 

 of hyphal tissue, the external portion constituting the enveloping 

 membrane. This arrangement obtains in various genera of Agari- 

 cinae, such as Agaricus (sub-genera Amanita, Fig. 182, Lepiota) 

 and Coprmus, and generally in the order Gasteromycetes. This 

 membrane is termed, in the case of the Agaricinae, a velum uni- 

 versale ; in that of the Grasteromycetes, a peridium. When it is 

 dehiscent, and the sporophore is stipitate, a portion of it remains 

 surrounding the base of the stipe as a volva. 



