690 



SCIENTIFIC RECREATIONS. 



lichens form the principal food of the useful reindeer, and " Iceland moss " 

 is represented as wholesome for man. Lichen is derived from the Greek 

 term for " wart." 



The FUNGI are Very important, and with them we will close our sum- 

 mary. They include the favourite mushrooms and poisonous toad-stools, with 

 many other "fungous growths," from the " mould" on the jam pot to the 

 mushroom. 



Some of these fungi are peculiar to the substances upon which they 

 exist, and are in numerous instances destructive. The microscopic fungus 



Puccinea graminis is the 

 parasite which fixes itself to 

 corn, and produces the dis- 

 ease known as mildew, and 

 the Uredo segetnm (another 

 microscopic fungus) causes 

 the " smut " ; the " bunt " is 

 caused by the Uuredo fcetida^ 

 and the u spur" or "ergot," 

 which attacks rye, is caused 

 by the Acinula clavis. These 

 fungi completely destroy the 

 grain of corn in which they 

 form, and propagate in the 

 most rapid manner ; the 

 ergot is moreover a dangerous poison to those who eat the bread made of 

 rye infected by it. The truffle is a kind of underground fungus, and is 

 esteemed a dainty. Mushrooms are also fungi, and several species are 

 sufficiently wholesome ; these are the field mushroom and the fairy-ring 

 mushroom. 



Any organic substance will shortly become covered with this " mould" 

 or mildew. The air is so full of the germs of animal and vegetable life that, 

 as it penetrates everywhere, the smallest supply must contain some germs ; 

 and these, under a powerful microscope, present most beautiful forms and 

 colours. We annex (fig. 822) some of these forms highly magnified. They 

 are deposited by the air, and the substance into which they happen to fall 

 determines the kind of life which is to inhabit it. A few of these spores only 

 come to maturity. 



We again take the liberty to quote Dr. Carpenter on this subject. 

 He says : 



" There are scarcely any microscopic objects more beautiful than some 

 of those forms of mould or mildew which are so commonly found growing 

 upon the surface of jams and preserves, especially when they are viewed with 

 a low magnifying power and by reflected light ; for they present themselves 

 as a forest of stems and branches of extremely varied and elegant forms, 



Fig. 822. a a, Mould from an old bone ; , Mould from jam. 



