350 Transactions British Mycological Society, 



its growth is at first epinastic, its margin being incurved and 

 pressed against the stipe (fig. 46). Thus the hymenium begins 

 to be formed within a special chamber. As the hymenial sur- 

 face increases and keeps pace with the growth of the dorsal 

 tissue of the pileus, the latter expands and exposes the gills 

 (figs. 4r, 2d', and 2d). The gills are formed by the continual 

 downward growth of some of the hyphae ; these bend outwards 

 and bear the elements of the hymenium. The gills are thus ex- 

 posed before the pileus is completely developed and before the 

 spores are mature. Spores can be obtained from sporophores, 

 which are about half an inch across, and liberation of the spores 

 continues until the sporophore is fully grown — a period of a 

 month or two. The mature spores are disseminated by the wind. 

 When the sporophore is nearing maturity, some of the terminal 

 portions of the hyphae of the dorsal surface separate, and thus the 

 upper surface of the sporophore becomes granular in appearance. 



The free margin of each gill is fringed by a number of cystidia, 

 some being club-shaped, while others are pointed and some bear 

 tiny branches (fig. 3). Among the basidia are occasionally seen 

 cystidia (figs, ya and yh), which resemble some of those fringing 

 the free margin of the gills; they are colourless and project out 

 beyond the basidia. 



With variations of temperature and moisture there is a varia- 

 tion in the amount of growth of the pileus, but under moderately 

 favourable conditions a sporophore takes about three months to 

 develop. An insufficient supply of air delays growth. 



The sporophore projects out horizontally from the substratum 

 (fig. 4^). If the position of a log is altered after young sporo- 

 phores with the beginnings of gills have appeared, the stipes of 

 these attempt to readjust themselves in order to place the pileus 

 in a horizontal position. 



The pilei are sometimes zoned and this depends on changes 

 in the humidity of the atmosphere, variations in the amount of 

 moisture causing alternate acceleration or retardation of growth. 



The yellowish-brown pigment is diffused through the cell sap 

 of the hyphae and is much deeper in colour just below the 

 cuticle of the pileus. In very young sporophores stipes and 

 pilei are very pale buff, but soon the colour of the pilei deepens 

 and subsequently becomes cinnamon. Intensity of colouring 

 appears dependent on light, for when sporophores are grown in 

 diffuse light (temperature and humidity being constant) they are 

 a uniform pale buff colour but in bright light cinnamon or tan. 



According to Atkinson*, the young sporophores of Panus styp- 

 ticus are phosphorescent, but no fruit bodies which were ex- 

 amined exhibited this phenomenon. 



* G. F. Atkinson, Mushrooms, p. 136. 



