174 Encyclopaedia of Gardening 



GREENHOUSE continued. 



Aspect. Span-roof houses should run north and south. Lean-to 

 houses should face south, or as near it as possible. 



Heating. This is a subject that must have careful consideration. 

 In large houses it is only a question of which particular fire-boiler 

 should be used, but with smaller structures the claims of oil and gas 

 may be considered. The smaller a fire-boiler is the more difficult 

 is the task of stoking it and dampering it in such a way as to keep it 

 alight for 9 or 10 consecutive hours. On this account oil heaters 

 may be chosen for very small houses. The types in which a lamp 

 and boiler can be fixed outside the house, and connected with a set 

 of pipes within, are safest. A slight smell of petroleum is not in- 

 jurious to plants, but thick fumes are deadly, and every one knows 

 how ready a flame is to " run up " spontaneously. Whenever an 

 oil stove is set inside a house, a wide wick, rubbed clean daily, should 

 be used, together with the best quality of oil. The light should be 

 kept low when first lit, and watched till the danger-point of running 

 up is past. For small-medium houses an upright boiler set in the 

 wall of the house, and connected with a flow and return 4~in. pipe 

 along two sides and one end, may be used. The pipes may be jointed 

 with india-rubber rings and end in an expansion cistern. They 

 should rise slightly from the boiler. For large ranges of houses a 

 flat boiler should be used. The setting and fitting of the pipes 

 should be a matter of contract in buying the heating apparatus. 

 Anthracite coal, or coke, may be used as fuel, with a little breeze 

 and refuse house cinders, for upright ones. Stoking can be learned 

 by practice and observation. The fire should have a bright bottom, 

 and the bars should be clear, last thing at night. The fire may be 

 topped with some small damp fuel. In a fiat-boiler furnace the 

 glowing embers should be drawn to the front, and the fresh fuel 

 thrown well back. The ashes should be cleared daily and the flues 

 once a month. 



Staging. The most durable flat stage, and the best for the plants, 

 is one consisting of large slates resting on a strong wooden frame- 

 work and surfaced with white shell or shingle. This can be kept 

 moist in hot weather. 



Shading. Shade is essential to some plants when grown under 

 glass, notably Ferns, Cucumbers, and many Orchids; and it may 

 be said to be beneficial for all in hot weather, while it lessens labour 

 by reducing the necessity for watering. Movable shading in the 

 form of tiffany or scrim blinds mounted on rollers which can be 

 drawn up under a cover at the top of the house in dull or wet weather 

 is the ideal. The larger seedsmen and nurserymen supply tiffany 

 and scrim; the latter makes admirable blinds. A cheap form of 

 shading is to paint the glass with one of the special preparations 

 sold by seedsmen. This must, of course, remain on in dull as well 

 as in bright weather. It should be removed in autumn. 



Green Manure. See Manure. 



Grevillea (Grevill-ea, after Mr. C. F. Greville. Ord. Proteaceae). 

 Grevillea robusta is a graceful plant, grown for the sake of its 

 slender branches and elegantly cut foliage. It is very useful for 



