CH. YI.] THE FLOWER. '207 



power of the leaves. For this reason the best glass 

 should always be employed in the sashes of the 

 hothouse, conservatory, and other stnictures of the 

 forcmg department. But the benefit sought for is 

 frustrated if that glass be not constantly well 

 cleansed. Tlie best glass, if dirty, allows fewer 

 rays of light to pass through than inferior glass if 

 kept bright. 



A thorough cleansing should be given both to 

 the outside and inside twice annually, during the 

 first weeks of March and of October, and a third 

 cleansing, on the outside only, at the end of June. 

 In proportion to the deficiency of hght, does the 

 plant under glass become, in the gardener "s phrase- 

 ology, drawn. That is, its surface of leaves be- 

 comes unnaturally extended, in the vain effort to 

 have a suf&cient elaboration of the sap effected by 

 means of a large suiface exposed to a diminished 

 light, for which a less surface would have been 

 sufficient if the light were more intense. The 

 plant with this enlarged sui'face of leaves becomes 

 unfniitful, the sap being expended in their produc- 

 tion, which should have been appropriated to the 

 formation of fruit. 



Mr. Williams made some experiments intended 

 to illustrate this point, and he found that varieties 

 of the vme, when grown under white, or crown 

 glass, under green glass and in the open air, had 



