212 AXIOMS AS TO DAMP AIB. 



state of rapid growth, a large amount of moisture in the aii- 

 will be prejudicial rather than advantageous to a plant ; if the 

 temperature is at the same time high, excitability will remain 

 in a state of continued action, and that rest which is necessary 

 wUl be withheld, the result of which will be an eventual 

 destruction of the vital energies. But, on the other hand, if 

 the temperature is kept low while the amount of atmospherical 

 moisture is considerable, the latter is absorbed, without its 

 being possible for the plant to decompose it; the system 

 then becomes, in the younger and more absorbent parts, 

 distended with water, and decomposition takes place, followed 

 by the appearance of a crop of microscopical fungi ; in short, 

 that appearance presents itself which is technically called 

 " damping off/' 



A skilful balancing of temperature and moisture in the air, 

 and a just adaptation of them to the various seasons of growth, 

 constitute the most complicated and diflScult part of a 

 gardener's art. There is some danger in laying down general 

 rules with respect to this subject, so much depending upon 

 the peculiar habits of species, of which the modifications are 

 endless. It may, however, I think, be safely stated that the 

 following maxims deserve especial attention : — 



1. Most moisture in the air is demanded by plants when they 

 first begin to grow, and least when their periodical growth is 

 completed. 



2. The quantity of atmospheric moisture required by plants 

 is, cceteris paribus, in inverse proportion to the distance from 

 the equator of the countries which they naturally inhabit. 



3. Plants with annual stems require more than those with 

 ligneous stems. 



4. The amount of moisture in the air most suitable to plants 

 at rest is in inverse proportion to the quantity of aqueous 

 matter they at that time contain. (Hence the dryness of the 

 air required by succulent plants when at rest.) 



