396 POPULAR SCIENCE MONTHLY. 



leaves, and another that remains below ground. It is this latter that 

 concerns us now, and it is worth study. This lower part consists of a 

 number of twigs called rhizomes, from which proceed a vast number 

 of fine, threadlike rootlets, and these are the mouths of the plant, 

 through which it draws nourishment from the earth about it. 



Before any living thing can use nourishment from without, it 

 must be dissolved, and this solution requires much preparation at 

 times. Men, and other animals with a wide range of food stuffs, effect 

 this by the secretions of the digestive organs; but most plants have no 

 digestive apparatus, strictly speaking, and were they supplied with 

 an abundance of the foods they most need, they would starve unless 

 the food were in a suitable state for absorption. 



The way in which Nature effects this solution is the key to many 

 of her secrets, and it has been understood only within the past few 

 years. If we have a piece of meat freshly taken from an animal we 

 find it firm, coherent, and almost odorless. If it be put into a warm, 

 moist chamber for a few days a great change comes over it, and it 

 becomes soft, offensive in odor, and liable to fall to pieces. We 

 say that it is rotten or putrid. If a bit of it be put under a microscope, 

 it is seen to be teeming with bacteria, and these are responsible for 

 the decay. Now, if a specimen of earth be examined, we find that 

 it contains bacteria, that attack all kinds of organic matter, tearing 

 it to pieces to get their food, and making many different things out of 

 what is left. There is one sort of ferment that grows in apple juice 

 and splits the sugar into alcohol and carbonic acid, forming " hard 

 cider," and if the fermentation stops at this point the well-known 

 drink results. However, there is another ferment called " mother 

 of vinegar " that may get in, and, if so, a different kind of fermenta- 

 tion is started that forms acetic acid instead of alcohol ; or the bacteria 

 of decomposition may come in and the whole go back to its elements. 



There is a wonderful provision of Nature shown in these stages. 

 The bacteria — the organisms that produce decay — can not live in a 

 strong sugar solution, but the ferments, like common yeast, can live 

 in it, and they split the sugar into alcohol, carbonic oxide, and other 

 things. In these another set can live, and when the first have died 

 of starvation or from the alcohol they form, the second set step in and 

 turn the weak alcohol into acetic acid. Acetic acid is a preserv- 

 ing agent, as our sour pickles show, but if it is not too strong there 

 are some organisms that can live in it, and the whole process ends 

 in decay. Now, it should be noticed that each of these organisms 

 paves the way for the next by converting an unsuitable food stuff 

 into a suitable one. 



This familiar example indicates the lines on which Nature works. 

 It is the same everywhere, and shows the advantage of specialization, 



