Modern Improvements in Horticulture. 297 



be preferred, because, in sucb case, shelter and warmth ATOuld 

 or could be united ; and from this it is evident, that the drier 

 the atmosphere, the drier will be the plants which are in it, 

 and consequently better able to resist refrigeration. 



There is a modern discovery, and means practised for the 

 preservation of fruit-trees from the effects of frost. The im- 

 mersion of frost-bitten extremities of the human frame to neu- 

 tralize its fatal effects, was the circumstance which suggested 

 the idea. This was first found useful in recovering frosted 

 potatoes, &c., but is now applied to wall-fruit trees, even when 

 covered with flowers, or their hardly-formed fruit ; and while 

 the trees are encrusted with ice, they are washed with water 

 from the engine to free them from it before the sun comes upon 

 them, which would otherwise be fatal*. But the best preventive 

 of frost from injuring wall-trees is the plan of covering the 

 wall with coping, which projects five or six inches over the 

 trees, and which prevents the perpendicular descent of cold, 

 or rather the right ascension of heat, thus rendering early wash- 

 ing unnecessary. 



It has already been hinted, that plants seem to require, at 

 least to take nocturnal repose ; there is also a diurnal repose 

 observable among plants, and visible by the collapsing of the 

 flowers, on or before a temporary obscuration of the sun's 

 light ; hence the provincial name of the pimpernel, ♦* go to bed 

 at noon," or the shepherd's weather-glass: because, when the 

 stimulating agents, heat or light, are withdrawn, the positions 

 of the leaves of plants and petals of their flowers are altered, a 

 certain flaccidity, especially of the foot-stalk of the leaves, is 

 seen, and nearly in the same way as when a due supply of 

 water at the roots is wanting : so plants which are not natives 

 of the torrid zone require a temporary or winter's rest. Now, 

 in our system of forcing, we change the natural seasons of our 

 plants, and, by furnishing them with an artificial spring, sum- 



* Why do the direct rays of the sun injure frozen plants, and why, if the frost 

 be Washed off by water, is the fatal effect of frost avoided ? 



The reason seems to be this : — water dissolves and withdraws the ciystallization 

 gradualiy, and without producing in the solution a greater degree of cold, whereas 

 the sun's rays produce a rapid solution^ and consequeutly a more intense degree o^ 

 cold, which is the destructive ageat. 



