JULY.. 251 



colour, above, from dull white to bright polished brown, like 

 mahogany. They grow on many trees, but seem chiefly to 

 affect the birch : they are also very frequently found on the 

 underside of upturned roots. From the elevated ridges on 

 the surface, forming parts of concentric circles parallel with 

 the edge, it would appear that they grow not by gra- 

 dual increase of the whole, but by additions to the outer 

 margin. Let us examine the structure of one of them, 

 which we shall find very curious. The upper part is of a 

 tough leathery consistence, often becoming hard and woody ; 

 the under part consists of a congeries of long capillary tubes, 

 parallel with and close to each other, fixed on the under sur- 

 face of the pileus or covering, and proceeding downwards at 

 right angles to it. These tubes, though minute, are so 

 straight, that if you cut off a piece of this part, and hold 

 it up towards the light, slowly turning it, the light will sud- 

 denly flash through them, when the orifices come opposite the 

 eye, as through a spy-glass. This mass of tubes is elastic, 

 and capable of taking up and holding a large quantity of 

 water, like a sponge. This Boletus constitutes the food of 

 some beetles ; if we examine more, we may probably find 

 some. 



C. Here are some ; they are monstrously ugly ; they 

 are nearly square, of a dark earthy brown colour, and 

 covered with rough, irregular prominences and depressions. 

 Some of them have two projecting incurved horns on the 

 thorax ; others have only slight prominences in their place. 



F. From their roughness, colour, shape, and sluggish 

 motion, I call them Toad Beetles ( Bolitophagus Cristatus) : 

 when molested, they draw in the antennae and legs, and lie 

 as if dead ; and certainly in that position it would require 

 an experienced eye to tell that they were living creatures at 

 all. 



C. Here are some large hollows in the porous part of 



