ACCELERATING VEGETATION. 359 



Protecting from rain requires the application of some description of 

 temporary roofing impervious to water. For beds or borders in the 

 open garden, frames, or hurdles, thatched with drawn wheat-straw or 

 reeds, may be employed, and these will also protect standard plants ; 

 or projected from the tops of walls, and supported by props in front, 

 they will protect from rain both the trees and the border in which they 

 are planted. 



Accelerating Vegetation. 



The acceleration of the growth of plants may be effected by the 

 position in which they are placed relatively to the rays of the sun, by 

 withdrawing moisture, by sheltering from cold winds and rains, by the 

 choice of early varieties, by pruning, and by the application of artificial 

 heat. For crops of herbaceous vegetables in the open garden, the 

 most general modes of acceleration are to cover with hand-glasses, 

 Rendle's Protectors, or other portable frames with glass roofs, and to 

 sow or plant in borders on the south side of east-and-west walls, and as 

 near to the wall as circumstances will permit. Next to walls, the south 

 sides of hedges or espalier rails are selected ; or, in default of either of 

 these, ridges in the open garden, in the direction of east and west, are 

 thrown up, their sides forming an angle of 45, and on the south side 

 of these the crop is sown or planted. The growth of early peas and 

 early potatoes is frequently accelerated in this manner, and also the 

 ripening of strawberries, as well as the early production of spinach, 

 lettuce, and other culinary plants ; and dry warm soil, culture in pots 

 by which the plants are rendered portable, and the selection of the 

 earliest sorts, are obvious adjuncts. 



Artificial heat, for the purpose of acceleration, is applied by means 

 of fermenting substances, as in hotbeds ; the combustion of fuel, as in 

 hotwalls and hothouses of various kinds, whether heated by flues, hot 

 water, or steam. The different kinds of hothouses and pits, and their 

 general management, have already been given, and we shall here con- 

 fine ourselves to what concerns hotbeds and pits heated by fermenting 

 materials. 



Hotbeds are chiefly made of stable-dung, but tanners' bark, cocoa 

 fibre and cotton refuse, leaves of trees, and especially oak leaves, mown 

 grass, weeds, clippings of hedges, and almost every other article capable 

 of putrescent fermentation, may be used either alone or with stable- 

 dung. Tanners' bark, cocoa fibre, or oak leaves, are found the prefer- 

 able fermenting materials for hotbeds in hothouses, because they 

 undergo less change in bulk, and retain their heat longer than dung or 

 any other fermentable substance that can be readily obtained in equal 

 quantities. Leaves do not produce such a powerful heat as bark, but 

 they have this advantage, that when perfectly decayed, they form a rich 

 mould, which is useful both as soil and as manure ; while rotten tanners' 

 bark is found rather injurious than useful to vegetation, unless it be 

 well mixed with lime or with earth, or left till it is thoroughly decayed 

 into mould. When it ceases, therefore, to be used in the hothouse or 



