a? 
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 welteng or 
drooping of ieaves, and 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 1s 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 ef 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 vecover 
again at night even without further water supply. When 
the leaves croop 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 avoidéd. 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 
