128 THE FORCING GARDEN. 
used for these with double the amount of hot-water 
pipes, and a boiler capable of heating them, to be 
double-glazed, with clips on my plan, according to fig. 
7 or 9. The double glazing of this house is essential 
for these plants, as they are, many of them, winter 
flowerers, and it is the best for such a class of tender 
plants, being safe, certain, and economical. If the 
house containing this class of plants does, or must, face 
the south, then select some appropriate climber for the 
south roof, and I know of none better suited for this 
purpose than an Allamanda, or a Jasminum, or a Bou- 
gainvillea glabra; each of these may be trained as you 
please, covering the roof with a certain number of 
permanent leaders and then spurred in as for a vine. 
Thus the climber may be made to cover the roof thickly, 
or to form a half-shade, which is the proper thing for 
Gesneraceous plants: too much shade is not good for 
them, but only so much as will break the full power of 
the light. 
In attempting to grow this class of plants, it is 
necessary to be careful and not to give the roots any 
water when they are first excited, but to allow them to 
make some little growth and then to give water suffi- 
cient to half-wet the soil all through. The drainage 
must be perfect, that is, one that will not admit of the 
settlement of any water, but allow it to pass off directly; 
thus the danger of too much water will be obviated. 
The tribe of Gloxinias are perhaps among our best 
Gesneraceous plants. They may be raised from seed, but 
as so few of them raised in this way are of much com- 
mercial value, it is quite a speculation to do so. It is 
much better to purchase a dezen or two well-known 
sorts and to propagate them by cuttings of the leaves 
