illustrate this point, and he found that varieties of 

 the vine, when grown under white, or crown glass, 

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

 meters of their leaves, in inches, altered as in the 



following table 



Glazing, or the mode in which the glass is inserted 

 in the frames, is a very important consideration ; for 

 if done imperfectly, moisture from rain, dew, or va- 

 pour condensed within the house, penetrates between 

 the rebate of the framework and the glass, or between 

 the laps of the panes themselves, and, expanding in 

 the act of freezing, unfailingly cracks them. Again, 

 if the panes fit tightly into the rebates, any sudden 

 expansion causes a similar fracture. 



We are of opinion that panes of glass seven inches 

 wide and twelve inches long are the best practical 

 size for hothouses. The glass should be clear, stout, 

 and selected as flat as possible, so that the panes 

 may lie perfectly level one upon the other, and so 

 cut that they may not fit too tightly against the ribs 



