EFFECTS OF CLIMATE. 13 



or ^^ chills and fever" among local residents. It is a 

 popular error to suppose, therefore, that the earth 

 destroys microbes, and it seems to have arisen out of 

 the fact that dry soil renders them for a time compara- 

 tively innocuous. 



The ground is the great resting and breeding place 

 of micro-organisms of all kinds, whether they be harm- 

 less or capable of producing disease. It is easy to 

 foresee, therefore, how they can pass into the atmo- 

 sphere or on to the surface of bodies, and thus be spread 

 everywhere. It becomes apparent, also, how animals 

 and plants may be alike affected by them, and how 

 rapidly they multiply under favorable conditions, which 

 may be briefly summarized as warmth, moisture, and 

 usually a deficiency of light. 



If we cover up a pit of potatoes without the precau- 

 tion of keeping down the temperature and moisture, 

 fermentation sets in, and soon fungoid growths are 

 everywhere perceptible, while the substance of the po- 

 tato becomes diseased and rots. If the atmosphere of 

 the greenhouse be kept too warm and moist, fungoid 

 growths begin to show themselves directly, and in due 

 time the plants become sick ; or, again, the same cir- 

 cumstances arise if two or three weeks pass without the 

 assistance of the sun's rays to purify the atmosphere. 

 Although this is well understood by persons who have 

 charge of flowers, I can imagine an objection which 

 those to whom the suggestions may be new would be 

 likely to raise. For most people have read of, if they 

 have not seen, the rank vegetation of the tropics, where, 

 amid an abundance of heat and moisture, often with an 

 absence of sunlight, the most luxuriant and healthful 

 vegetation that the world knows, may be discovered. 

 Or, again, we may go into the deep woods in our own 

 country, and there, in shaded nooks and corners, find 

 specimens that are not to be found elsewhere, and 

 which, notwithstanding their healthy appearance, will 

 wither and die as soon as they are transferred to the 

 garden bed. 



