224 FOOTNOTES FROM 



species have the power of indefinite extension and locali- 

 zation, but, as a whole, like the higher cryptogams, they 

 can only spread within certain limited areas. In tropi- 

 cal forests, where the heat fills the stifled and confined 

 air with moisture, where the exuberance of the vegetation 

 excludes the rays of the sun and creates the "dim religi- 

 ous light " which they love, and where, more especially, 

 there is always an immense quantity of decaying organic 

 matter ; in such favourable situations we might expect 

 to find them in the greatest quantity and luxuriance. 

 But, strange to say, fungi as a class, are comparatively 

 rare in tropical woods. While every tree has its creeper, 

 and almost every flower its parasite, the plants which, 

 above all others, are most parasitical have very few re- 

 presentatives there ; and dead trunks and prostrate 

 boughs, and decaying herbage, rot and crumble away 

 untouched by the ravages of mushroom or mould. In- 

 sects in these countries perform the office of fungi in 

 hastening the decomposition of dead matter, and incor- 

 porating and deodorizing the decaying particles ; and it 

 must be confessed that they perform this duty more 

 speedily and effectually ; while, unlike the fungi, they 

 leave no unpleasant traces, no putrifying masses behind 

 when their work is accomplished, and their own turn 

 comes to die. Like some of the epidemic diseases, as, 

 for instance, typhus, with which they are said to be 

 connected, the too high temperature of the tropics seems 

 to offer an effectual barrier to their general distribution 

 in those countries. Their head-quarters seem to be in 

 northern latitudes, where the temperature is mild and 

 genial, and where there is a constant supply of moisture. 



