64 The Scottish Naturalist. 



STEUOTUEE OF THE COMMON MUSHEOOM. 

 By WORTHINGTON G. SMITH, F.L.S.* 



THE entire substance of the common Mushroom is made 

 up of excessively small bladder-like cells ; these cells 

 are so small in size and light of weight, that no less than 

 1,500,000,000,000 (one and a half billions of cells) go to every 

 ounce of the Mushroom's weight. Mushrooms are generally 

 grown by dealers from spawn or mycelium ; this spawn is nothing 

 but living matted cells in a resting condition, needing warmth, 

 moisture, and darkness only for vivification. Mushrooms may, 

 liowever, be grown from the purple-black dust which falls from 

 their lower surface. This black dust again simply consists of 

 nothing but cells, but in this case the cells are called spores. 

 These latter are of a somewhat different nature from the simple 

 cells of the flesh of the Mushroom, and their outer coat in this 

 species is changed in colour from transparent to purple-black, 

 possibly from contact with the air. 



The cells in the stem of the Mushroom are sausage-shaped, 

 and grow vertically ; on reaching the cap these cells spread 

 over in an umbrella fashion, and descend into the internal 

 substance of each individual gill. This internal mass of cells 

 within the gill is termed the "trama "by botanists, (a. a. Fig. I.) 



To understand how the Mushroom produces its seeds or 

 spores, a slice should be cut off the side of the cap of a ]\Iush- 

 room from the top downwards. Where the sectional part is 

 now exposed, the gills which are cut through will look like so 

 many small fine teeth of a comb. With a sharp lancet a very 

 small thin transparent fragment must now be sliced off from 

 the top downwards, and placed upon a glass for examination 

 under the microscope. 



When magnified 250 diameters this fragment will be seen, as 

 in Fig. I., to consist wholly of simple cells. The sausage-shaped 

 cells of the stem which have spread over the cap and descended 

 into each individual gill are seen between the letters a, a. These 

 "trama " cells are of some importance, because certain members 

 of the Mushroom-tribe have no larger cells of this nature. As 



* Read at the meeting of the Cryptogamic Society of Scotland, September 

 1S76. We are indebted to the Editor of the Gardcneis' Chronicle for 

 electrotypes of the figures. 



