34 
have been established that it is probably the intensity 
rather than the quality of light which is required for 
flower production. Another factor which is important in 
this respect is the concentration of organic materzal in the 
stem and leaves of the plant, while an increase of water 
and inorganic salts tends to the development of foliage 
rather than flowers. It is for this reason that a reduction 
in the supply of water is so helpful in producing abundant 
flower buds. It is sometimes thought that a wealth of 
blossom on our fruit trees predicts a fine summer; from 
what has been said above, it is obvious, however, that it is 
the fine summer or dry autumn of the previous year which 
is responsible for the prolific bloom. Flower buds on our 
fruit trees are, of course, already developed in the late 
autumn. Dealing with herbaceous plants, it has been 
found possible to arrest the development of flowers even 
if the flowering shoot has commenced to make its appear- 
ance. Thus in specimens of the common House Leek a 
rosette of vegetative leaves may be caused to appear on 
the fiower shoot if the plant 1s copiously watered and 
uluminated with light passing through a red or blue 
screen. Conversely, the runners of some plants may be 
made to bend upwards and develop flowers if water is 
withheld and the plant placed in a very bright light. 
The horticultural practice of pruning and root pruning 
is also intended to further floral development. Each tree 
or shrub must be treated differently according as to 
whether flowers normally make their appearance on long 
shoots or on spurs, 2.2. on new or old wood. The removal 
of non-flowering shoots is therefore what is aimed at. In 
summer pruning the stoppage of the growth of purely 
vegetative shoots will actually stimulate the older 
branches to form flowers, as they will have an increased 
amount of food material at their disposal. The increased 
production of flowers effected by roct pruning is often 
remarkable. It will be sometimes observed that apple 
and other fruit trees produce long and vigorous new 
shoots, particularly in an upward direction, which are 
caused by the development of deep roots able to obtain 
an abundant supply of water even in fairly dry soil. The 
removal of these deep roots stimulates the growth of 
fibrous roots in shallow soil, where there is a less abundant 
supply of water in the summer and early autumn; the 
result of root pruning is therefore the production of 
