CLASSIFICATION 77 



appearance due to the presence of any excess of water in the sub- 

 stance of the cap is that termed " pellucidly striate." A truly 

 striate cap means that shallow ridges and furrows alternate ; but 

 in a pellucidly striate cap, whicli can only exist when the cap is 

 saturated with water, there only occur alternating parallel darker 

 and lighter streaks on the cap, the surface being quite even. This 

 appearance is due to the fact that those portions of the cap be- 

 tween the gills is thinner in flesh than those portions of the cap 

 from which the gills originate ; hence the thinner portions of the 

 cap, between the gills, hold less moisture than those portions from 

 which the gills spring, and are consequently paler in colour. In 

 other words, the darker lines correspond to the position of the 

 gills springing from the cap. Hygrophanous or water-absorbing 

 species of fungi occur in many other genera of fungi in addition 

 to Omphalia, and the above explanation applies to all such. In 

 many species of Omphalia the gills are remarkably distant, that is, 

 wide apart, and in such cases they are generally comparatively 

 thick at the point where they spring from the cap, but become thin 

 and sharp or acute at the edge. With very few exceptions there 

 are very few bright-coloured species in the genus under considera- 

 tion. None are recognized as being of any value from a culinar}/ 

 point of view. Neither taste nor smell are marked features of the 

 genus. 



Many of the species grow on twigs, wood, etc., although some 

 are met with amongst sphagnum, etc., in swampy places, and 

 others grow on the ground. Some of the species are amongst the 

 smallest fungi known. 



Pleujoiiis 

 All the species grow on wood. In the most typical forms the 

 gills are decurrent, often very deeply so, and in some instances 

 the gills anastomose or join on to each other when they reach the 

 stem, and are there inclined to form irregular pores. In some 

 species the gills end abruptly behind, and do not run down the 

 stem in a decurrent manner. Yet there is a certain combination 

 of characters which collectively suggest the genus Pleuroius. The 

 stem is sometimes quite lateral, or springing from the edge of the 

 cap ; in other species the stem is excentric, or originating from a 

 point near to the edge of the cap, but not from the centre, hence 

 the cap itself is more or less unsymmetrical. In some of the simpler 

 forms the stem is absent, and the cap is attached by its. edge to 

 the substance it is growing upon. Again, in the most highly de- 

 veloped forms there is a more or less evident ring on the stem. 



The species vary greatly in size, some being amongst the largest 

 of our agarics ; while otlier minute forms growing on moss, etc., 

 are only two or three lines across. Pleuroius oslrcalus, so called 

 on account of the more or less oyster-shell shaped cap, is included 

 amongst the best and safest of our edible fungi. 



