452 Cucumber^ Melon, and other Forcing-Pits^ 



capable of living in dry situations, which really is in general 

 the case. 



Leaves have the power of absorbing moisture as well as of 

 emitting it, which power of absorption they principally enjoy 

 during the niffht. 



During the day leaves also absorb carbonic acid gas, which 

 they decompose, retaining its carbon, and emitting the greatest 

 part of the oxygen that enters into its composition. In the 

 night this operation is in a certain measure reversed, a small 

 quantity of oxygen being absorbed from the atmosphere, and 

 a yet smaller proportion of carbonic acid emitted. 



The hints and warnings which these facts suggest to the 

 mind of every reflecting practitioner are numerous. They 

 explain and enforce the necessity of a regular, and by no 

 means as to quantity indiscriminate, supply of water to plants; 

 the importance of shading after their transplanting, and of a free 

 circulation of air. Sec. ; and the necessity of keeping the leaves 

 as clean, and as free from injury, as possible. The leaves of 

 plants must often be removed, and in some instances this is done 

 with essential benefit, but the horticulturist shx)uld constantly 

 keep in mind that with every one that he removes he deprives 

 the plant of a primary organ of its existence. Light, it has 

 been just slatedj is the cause of the green colour of plants, but 

 it should be observed that its full power is only beneficial when 

 directed upon their upper surface. This is evidenced by the 

 position they always maintain. If the branches of a tree, 

 trained against a wall or other support, are so moved, when 

 their leaves are completely expanded, that the under side of 

 the foliage is most exposed to the light, they are always found 

 to regain their natural position in a day or two. If the expe- 

 riment is often repeated on the same individual^ the leaves to 

 the last continue to revert, but become gradually weaker in 

 the effort, partially decay, and their epidermis peels off. Suc- 

 culent leaves are particularly sensible of light, but those of 

 pinnated leguminous plants are still more so» 



{To be continued.} 



Art. II. A descriptive Sketch of the Cucumber, Melon, and 

 other Forcing-Pits, generally in Use i?i Welbcck Garderp^ 

 Nottinghamshire. By Mr. Henry Thompson, Under- 

 Gardener in the Forcing Department. 



Sir, 

 Agreeably to the direction of Mr. Thompson, I send you 

 a plan and sections of the forcing-pits in use here for general 

 purposes. You will perceive that there is a saving of materials 



