1884-85.] Edinburgh Naturalists' Field Club. 213 



In Agarics find Polypori growth does not start till some time after 

 their emission. A time of rest seems necessary before germination 

 begins to operate, and if placed in suitable conditions, vegetation 

 is then not slow to show itself. We see at first, coming from one 

 or two projections opposite to the spore, a filament or radicle, which 

 soon divides and multiplies into branches more or less numerous, 

 and almost invariably white. These cross each other, intermingle, 

 and form what is called mycelium, or white of Mushroom. On the 

 mycelium there soon appears, when the conditions are favourable, 

 the Mushroom proper, which, from its birth, has generally a globu- 

 lar or ovoid form, but as it increases it gradually assumes the form 

 which characterises the species to which it belongs. The embryo 

 Mushroom is surrounded with a membranous or hairy covering, 

 which afterwards disappears. One or two membranes more or less 

 persistent, called the volva and ring, protect the young plant till 

 its complete development. The ring is somewhat similar to the 

 calyx and petals of the higher plants, and is probably a place of 

 shelter for the spores, which are perhaps fecundated before they are 

 detached from the cap. Bulliard says the young Mushroom bursts 

 through the volva and detaches itself from the ring sometimes with 

 a noise as loud as that of a pistol. Cold destroys neither mycelium 

 nor spores, and a dry heat of upwards of 100^ does not kill the 

 germinating faculty of the spores of most species. Mycelium and 

 spores remain often latent for years until circumstances intervene to 

 favour their development. Kept in a dry spot, the spawn retains 

 its vegetative property for a long period. Gardeners state that 

 they have kept it for several years, and then put it in beds, and 

 quantities of Mushrooms have been produced. When once the 

 Mushroom, however, has begun to develop, either intense cold or 

 heat kills it. Very few species of fleshy consistence can resist the 

 frosts of winter or the ardent heat of a dry summer. Mushrooms 

 require a degree of temperature and moisture of certain definite 

 limits in order to develop, and germination takes place only at 

 fixed times of the year. Spores placed in unfavourable conditions 

 do not germinate while these continue. In my garden the tufted 

 Agaric has sprung up every autumn successively for the last five 

 years, but this year germination has failed, owing perhaps to the 

 dryness of the season. 



Mushrooms are composed of interlaced fibres forming a net-like 

 tissue, whose round or elongated cells communicate with external 

 agents by means of minute pores. By these absorption and ex- 

 halation are performed. They have no proper vessels, like ph;\?no- 

 gams, for the circulation of sap. In these cells, of which the whole 

 plant is composed, the nutritive fluids are contained, whose circu- 

 lation, almost insensible, is performed by a sort of capillary attrac- 

 tion. The fluids penetrate by endosmose and are expelled by 



