H MICROSCOPIC PLANTS. [CHAP. 



putting on a cover-glass, examine it with a high 

 power, we shall see a multitude of these little plants 

 arranged in strings and heaps. Each plant ranges 

 in size from ^j^th to yoWth part of an inch across, 

 or an average of about 7 ^V^ tn - ^ n other words, it 

 would take 3000 of these plants, placed side by side, 

 to cover the length of an inch. They increase in 

 numbers by budding. A slight protuberance arises 

 at one part of the cell-wall, and, rapidly growing, 

 assumes the same form and size as the cell from 

 which it sprung; though, perhaps, before it gets so 

 large, it has itself produced a bud, which has in turn 

 produced another. So they multiply at an enormous 

 rate, and their growth causes the fermentation of 

 fluids containing sugar, which, by the subtraction of 

 some of its elements, is changed into alcohol, the 

 intoxicating element in beer, wines, and spirits. These 

 Torulse are capable of being dried into a powder, and 

 in such a condition they form an article of commerce, 

 for their vitality is not impaired. They may be kept 

 in this state for a considerable period, but on intro- 

 ducing a very small quantity into a sugary liquid, 

 fermentation will ensue almost immediately as the 

 result of their renewed activity and growth. We 

 have ourselves kept yeast for nearly three years 

 without injury to it. 



But it is time we advanced a step in the considera- 

 tion of these minute fungi. We have here a specimen 

 of green mould, such as grows on all decaying sub- 

 stances old bread, old boots, jam, dead leaves, &c. 

 Carefully selecting a small portion, we place it under 

 a low power, and find something like our illustration. 



