Ui SEASON OF GROWTH DEMANDS WATER. 



morning, yet at the time of its formation the plants are often exposed to 

 a very intense cold. 



A singular effect, somewhat similar in nature, though caused in a 

 very different manner, is sometimes observed ; as clear still water offers 

 no obstruction to the passage of radiant heat, it occasionally happens 

 that water plants are injured by the great heat of the sun's rays ; like 

 land plants they receive abundance of radiant heat from the sun, but, 

 imlike land plants, they do not experience the compensating effect of 

 evaporation ; they only feel the less perfect cooUng influence of the sur- 

 rounding water. It therefore occasionally happens that plants growing 

 in water, and surrounded by it, are burnt and scorched by the heat of 

 the sun's rays, the radiant heat of which produces no effect on the water 

 through which it passes, any more than it does in passing through the 

 air ; its effects only become evident when its rays fall upon a solid 

 substance, such as the surface of the ground or the leaves of a plant. 



It is wlien plants are in a state of growth that an abundant 

 supply of moisture is required in the earth. As soon as young 

 leaves sprout forth, perspiration commences and a powerful 

 absorption must take place by the roots ; the younger the leaves 

 are, the more rapid their perspiratory action; their whole 

 epidermis must, at that time, be highly sensible to the stimu- 

 lating power of Hght : but as they grow older their skin hardens, 

 the stomates become the only apertures through which vapour 

 can fly off, and by degrees even these are either choked up, or 

 have a diminished irritability. As a general rule, it is safe to 

 conclude that the ground should be abundantly supplied with 

 moisture when plants first begiajto grow, and that the quantity 

 should be diminished as the organization of a plant becomes 

 completed. There are, however, ' some especial cases which 

 appear to be exceptional, 'm consequence of the unnatural state 

 in which we require plants to be preserved for our own peculiar 

 purposes. 



It has been remarked by one of the translators of this work that " care 

 should be taken that plants in pots have not too great a quantity of 

 moisture when they first begin to vegetate." Plants should not have too 

 much moisture at any time. The meaning of the caution seems to be 

 that, as plants in bud are less able to assinulate moisture than if in 

 fuU leaf, so the supply of moisture to the former should be in proportion 

 small. But this caution is needless if the cultivator recognises the 

 general axiom that " Plants should nevek hate moee moisiitbe 



