33^ 



THALLOPHYTES. 



the under-side of the pileus ; and from this the radial hymenial lamellae grow downwards 

 (///, /), filling up the air-cavity. The hyphae run from the base of the whole fructification 

 to the margin of the pileus, forming the outer wall of the air-cavity; the tissue lying in 

 the centre elongates into the stalk {IV, st), while the distance from it of the margin of 

 the pileus constantly increases ; the hyphae which lie beneath the air-cavity that con- 

 tains the lamellae become stretched in consequence, and separate from the stem from 

 below upwards, forming a membrane {V, v), running from the upper part of the stalk 

 beneath the lamellae to the margin of the pileus, into which their hyphae are continued. 

 When at length the pileus extends horizontally from the elongation of the tissues, the 



membrane (velum) becomes detached 

 from its margin, and hangs from the 

 stem like a ruffle {annulus). (Compare 

 also Fig. 79, p. 96, Boletus Jlanjidus .) 



The hymenium, as has already been 

 mentioned, covers the surface of the 

 lamelliform, peg-shaped, or tubular 

 projections of the under-side of the 

 pileus. A transverse section of the 

 latter across the hymenium gives, in all 

 three cases, nearly the same figure, as 

 is seen in Fig. 227, drawn from Agaricus 

 campestris. A shows a piece of the disc 

 of the pileus cut transversely, h the 

 substance of the pileus, /the lamellae; 

 in 5 a piece of a lamella is more strongly 

 magnified , to show the course of the 

 hyphae. The substance of the lamella, 

 called the Trama (t), consists of rows 

 of long cells, which diverge from the 

 centre right and left to the outside, 

 where the cells of the hyphae are short 

 and round, and form the sub-hymenial 

 layer {sb in JB and C). From these short 

 cells spring the club-shaped cells (q), 

 densely crowded and at right angles to 

 the surface of the lamella, forming 

 together the hymenial layer {B, by). 

 Many of these remain sterile, and are 

 called Parapbyses, others produce the 

 spores and are the Basidia, Each basi- 

 dium produces in this species only two, 

 in other Hymenomycetes usually four 

 spores. The basidium first of all puts 

 out as many slender branches {/) as 

 there are spores to be formed ; each of these branches swells at the end, the swelling 

 increases and becomes a spore (j", s'"), which falls from the stalk on which it was 

 placed, leaving it behind {s""). 



On the formation of the tissue of this group only one further remark need be made ; 

 that in the fructification of some Agaricinae {e.g. Lactarius) some of the much-branched 

 hyphae are transformed into laticiferous vessels, from which large quantities of latex flow 

 out when they are injured. 



(4) The Gasteromycetes ^ agree with the previous group in the mode of formation 



Fig. 227. — Agaricus campestris; structure of the hymenium; A, B 

 slightly magnified ; C a part of 5 (X 35o)' The protoplasm is indicated by 

 fine dots. 



* [De Bary, Morphol. und Physiol, d. Pilze, 1866. — Brefeld, Basidiomycetes, p. 175.] 



