100 MANAGEMENT OP GREEN-HOUSE PLANTS. 



a plant in almost any situation, it will invariably show a ten- 

 dency to turn to the light; the sunflower is a sti iking exam- 

 ple of this singular fact. .As the leaves supply the plant 

 with air, and the fibres of the roots with nourishment, to 

 strip off the leaves or destroy the fibres is to deprive it of 

 part of its means of support. 



Having shown that air and water are essential to vege- 

 tation, and light to its colour, experience shows us that 

 heat, in a greater or less degree, is not less necessary to 

 the growth of plants ; it is therefore requisite, that in 

 taking plants into our rooms, we should attend to these par- 

 ticulars. ^ 



The internal structure of plants consists of minute and 

 imperceptible pores, which serve the same important pur 

 pose in the vegetable, as veins in the animal, system ; they 

 are the medium of the circulation of the sap in the former, 

 as the veins are of the blood in the latter ; but it is by no 

 means settled as yet by physiologists how the food of plants 

 is taken up into the system, and converted into their con- 

 stituent parts. 



From the foregoing considerations and facts, it is evident, 

 that, as air, heat, and moisture are each essential to vegeta- 

 tion, water should only be given in proportion as heat and 

 air are attainable. In the summer season, green-house 

 plants may be exposed to the open air, from the early part 

 of May until the end of September, by being placed on the 

 ledges of windows, or on a stand erected for the purpose, 

 or, in the absence of a nursery bed of flowering plants, they 

 may be introduced into the regular flower-beds, to supply 

 the place of such plants as may wither and die in the course 

 of the summer, by being turned out of the pots and planted, 

 or plunged in the earth with the pots. 



In the heat of the summer season, plants generally re- 

 quire water every evening, and in the absence of dews, the 

 earth about their roots may sometimes need a little in the 

 morning; but experience shows, that the roots of plants 



