THALLOGENS FINISHED. 31 



the under side of the mushroom cap (Fig. 22) ; the Tubes, or 

 pipes, in Boletus ; the Processes, or teeth, in Hydnum. The 

 spores are sometimes in a closed cavity called a Conee.ptaole ; 

 the Hymenium is then called a Clinode {olinodium), or 

 couch. The flower-cluster is sometimes enclosed in a volva 

 (pouch), as in Agaricus campestris (Fig. 22) ; this bursts as 

 the cap grows. The slime-moulds and the puff'-balls (Lyco- 

 perdon. Boletus, etc.) have an outer cover around the re- 

 ceptacle. This cover is called Peridium ; it is sometimes 

 double, its outer coat separating into regular parts from 

 the top to the base of the stipe, as in the Earth-star (Geas- 

 ter), making a star-shaped, flower-like figure with a puff-ball 

 in its centre. The flowers are monoecious. The antheridium 

 grows near the oogonium; it never develops antherozoids, 

 but blends its protoplasm with the contents of the oogonium 

 without previous change. Gemmation (budding) occurs, as 

 in the Yeast Plant (Fig. 18, XX). Virgin reproduction takes 

 place by means of Conidia, which are simple cells producing 

 zoospores (these are elegantly seen in Fig. 19) ; and by 

 Stylospores (stalked spores) included in a conceptacle called 

 Pyonide^ Simple cells called Spermatia (enclosed in a con- 

 ceptacle called Spermogonium) are secondary male flowers. 

 The ripe spores of Fungi are so minute they resemble smoke 

 in escaping. Slender threads (called Paraphyses) often ac- 

 company the spore-cases here, as well as in Lichens and' 

 Mosses. 



56. The Lichens are closely related to Fnngi, but they 

 have a thallus. This has four layers : 1. Cortical (barky) 

 layer, called Epithallus ; 2. Gonidial layer, consisting of 

 bright green cells containing chlorophyl, and called Gonidia; 

 these gonidia are protophytes (like Protococcus, etc,), on 

 which all lichens are parasitic, whether tlie lichen be fixed 

 or aerial. 3. Medullary layer, composed of interlacing fila- 

 ments (hyphse). 4. Hypothallus, covered with root-like 

 hairs (Fig. 25). The conceptacles holding the female flowers 

 are called Apotheda (Figs. 23, 25"). The males are in con- 

 ceptacles called Spermogonia. They produce Spermatia, 

 equivalent to Antherozoids, but motionless. Some lichens 

 are air-plants; and many are edible. They prefer cold 

 climates, though many inhabit the tropics. They are 



