assimilation, the loss of water from a large leaf surface 

 might be more rapid than the absorption of water by the 

 roots. Whenever this happens it causes the wilting or 

 drooping of leaves, arid should that occur too frequently 

 the plant will not survive. As it is, wilting- of leaves in 

 the open occurs in hot summer days and affects mainly 

 plants with large delicate leaves, large at all events in 

 proportion to their roots, such as Doronicums, Calceolarias, 

 and young Cauliflowers. In the case of pot plants, which 

 are not only losing water through their leaves but also 

 through the sides of the porous pots, it is a common 

 phenomenon to find plants wilting during the heat of the 

 day, and to prevent this it is necessary to shade the houses 

 during the summer months, at least on very bright days. 

 Wilting is particularly noticeable in recently transplanted 

 plants, in which there is always sure to have been some 

 injury to the roots so that absorption cannot keep pace with 

 transpiration. Transplanting is therefore best undertaken 

 in wet or dull weather, or at the end of the day, when 

 during the succeeding night the stomata of the leaves will 

 be closed, and consequently at the start, at all events, there 

 will be no undue loss of water. Cuttings which have not 

 yet produced an adequate supply of roots require in 

 many cases to be kept in a moisture-laden atmosphere in 

 a frame. It is interesting to note that when plants in the 

 open flag at noon on a hot summer's day, they recover 

 again at night even without further water supply. When 

 the leaves droop the stomata usually tend to close, and 

 at night they are certainly closed so that the roots have 

 then the chance of replenishing the drooping leaves with 

 water. Watering the plants while the sun is still on them 

 should be avoided. Drops of water on the leaves are apt 

 to act as lenses and focussing the rays of light upon the 

 leaf often cause burning of the tissues and consequent 

 spotting of the leaves. Watering the soil has also some 

 dangers unless properly done. Merely damping the sur- 

 face of the soil, apart from the tendency to cause it to 

 cake, stimulates the growth of surface roots, which will 

 constantly require watering in dry weather. It is better 

 to give plants a good soaking from time to time. The 

 water penetrating to some depth causes the development 

 of deep roots, which will keep the plant supplied with 

 water even in dry weather. 



It is often thought that leaves, or at any rate the leaves 



