698 THE BOOK OF GARDENING. 



various plants as they flower : this is known as the " green- 

 house " or " show-house," and before proceeding further it will 

 be as well to give a description of this and the other structures 

 to be used. 



The Greenhouse. — This differs from a conservatory in that 

 all, or nearly all, the plants employed for furnishing it are 

 portable, whilst in a conservatory they are permanent, consisting 

 mostly of large subjects grown in beds ; but a combination of the 

 two may be managed, and is very effective. 



The structure should be as light and airy as possible. For 

 this purpose it is best to employ plenty of iron-work, having no- 

 large heavy wooden rafters or sash-bars to obstruct the light. 

 Of course, this mode of construction is expensive at first, but 

 will be found far cheaper and durable than wood in the end, in 

 addition to having the advantage of admitting more light. When 

 wood is used, teak will be found most serviceable, being both 

 very strong and durable. 



The span-roof form of house is preferable to the lean-to, for 

 it has the advantage of admitting light on every side, while in 

 the case of a lean-to light is on one side, and the plants will all 

 grow in that direction, necessitating frequent turning to maintain 

 their shape. The house should only be of moderate height — 

 about 12ft., and having a lantern about 2ft. wide, rising 2^ft. 

 higher at the top, making the actual height in the centre i4^ft. 

 The width may vary according to convenience, but 16ft. will 

 be suitable. There should be shelves 3ft. wide at the sides, 

 two 2jjft. paths on each side, and a central bed 5ft. wide. The 

 height of the sides may be 6ft., half being glass, resting on a 

 wall 3 ft. from the ground. 



The side shelves or stages should come to within 6in. of the 

 top of the wall. They are best made of slate with a few holes 

 bored in about i8in. apart, and having a raised rim all 

 round the edge. These should be filled with well washed small 

 gravel stones. Wooden shelves are not to be recommended : 

 they soon decay if not well looked after, and in so doing make 

 harbouring places for all manner of insect and fungus pests, 

 which are most injurious to plants. Shelves or stages made of 

 wooden battens, with spaces in between, should never be used, 

 as they allow water to run away at once, and by permitting dry 

 air to come from below, and to circulate freely amongst the pots,, 

 cause too rapid evaporation. Thus in hot weather constant 

 watering will be necessary, or the plants must be stood in 

 saucers, which is not advisable, as in that case the water does 

 not run away at all, and the pot is liable to become water-logged, 

 causing the soil to become sour. In the case of slate covered 

 with loose gravel stones, the stones allow water to run freely from 

 the pot, but yet retain it ; thus continual evaporation takes place, 



