FIXED STRUCTURES FOR GROWING PLANTS. 151 



culture of the compartments. In open, airy situations where hedges 

 for shelter are desirable, trellises of this sort might frequently be 

 adopted as substitutes both in kitchen -p. - 22 



and flower gardens. Single lines of 

 trellis-work, or even of frames to 

 be filled in with wire network, might 

 also be adopted as sources of shelter in 

 spring ; and in summer they might 



be covered with kidney-beans, peas, '.7!r.'.'.'".'.7Z 



gourds, tomatoes, nasturtiums, &c. 



The wire netting to fit into such "T."."^!;i!".."." 



framework can be made by common 



country workmen and their families, 



as is the case in various parts of 



Norfolk, both with hempen and wire 



netting, for hare and rabbit fences, 



and for folding sheep. (See < Gard. Plan Bowing the intersection of 



Mag.,' vol. xv. page 222.) trdlised walks ' 



Fixed Structures for Growing Plants, with Glass Hoofs. 



Plant-houses are required in gardens for forcing the productions of 

 the open air into maturity earlier than would otherwise be the case ; 

 for retarding these productions, as in ripening grapes late and pre- 

 serving them through the winter hanging on the tree ; and for the 

 growth of plants of warm climates. Hence it follows that all the requi- 

 sites for growing plants in the open air in their natural climate must 

 be imitated in plant-houses. As the grand difference between one 

 climate and another lies in difference of their temperature, one prin- 

 cipal desideratum in hothouses is to supply heat, without which little 

 can be done either in forcing hardy plants, or in preserving those of 

 warm climates. Next to heat, moisture is the most important agent in 

 growth, and that element is readily supplied both to the soil and the 

 atmosphere ; but though heat and water are sufficient to induce 

 growth, it cannot be continued or perfected without the influence of 

 light, and fortunately this is now, in a great degree, at the command 

 of art. Nearly the whole light of the climate is now admitted into our 

 artificial plant-houses, without dilution or diminution, through our 

 clear glass roofs. For growing certain fungi, and for forcing some 

 roots, very little light is necessary ; and where ripened crops of 

 fruit are to be retained on the trees and retarded, light, at least direct 

 solar light, may be in a great measure dispensed with. The retention 

 or production of heat therefore, and the admission of light, are the 

 great objects to be kept in view, in deciding on the situation, form, and 

 construction of hothouses. 



In the selection of a situation with reference to the surrounding 

 country, the north side of a sheltered basin, on the south side of a hill 

 and open to the south, with a dry warm soil, is to be preferred. The 

 object ol this choice is to have as little heat as possible carried off, 



