FLOWER-GARDENING. 95 



situation, it will invariably show a tendency to turn to the 

 light. The sunflower is a striking example of this singular 

 fact. As the leaves supply the plant with air, and the fibres 

 of the roots with nourishment, if we strip off the leaves, or 

 destroy the fibres, we deprive it of part of its means of sup- 

 port. 



HEAT ESSENTIAL TO THE GROWTH OP PLANTS. 



Having shown that air and water are essential to vegetation, 

 and light to its color, 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 particulars. The internal 

 structure of plants consists of minute and imperceptible pores, 

 which serve the same important purpose in the vegetable, as 

 veins in the animal, system, which are the medium of the cir- 

 culation 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 physi- 

 ologists, how the food of plants is taken up, and converted into 

 their constituent 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 win- 

 dows, 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. 



WATERING PLANTS. 



In the heat of the summer season plants generally require 

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



