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fore, for our experiments, we should attend to 

 their organization : annuals bear exposure better 

 than perennials ; and those abounding in sap, 

 having a spongy porous wood and much pith, 

 succeed with difficulty. It seems advantageous 

 that the plants to be tried should be deprived of 

 moisture as much as possible. Mr. Street found, 

 that, when planted above drains, several reputed 

 green-house species have flourished most luxuri- 

 antly. Plants do not suffer from frost in dry 

 situations, nearly so much as they do in moist, 

 or when an excess of rain is followed by a severe 

 frost. The reason is evident, in moist situa- 

 tions, part only of the moisture is evaporated 

 during the day, the rest remaining to be converted 

 into ice by the cold of the ensuing night. This 

 icy covering increases the cold, till the vital prin- 

 ciple, and resistance given by the formation of 

 the bark to the entrance of cold, are overcome ; 

 the sap is frozen, and the vessels burst by the 

 expansive force of freezing. 



Plants, in a warm climate, perspire more than 

 in a cold one ; so that in the one they require 

 much, and in the other little moisture. The in- 

 habitants of a hot-house must be abundantly 

 supplied with water to replace the constant eva- 

 poration that is going on ; but, on being trans- 

 planted to a colder climate, they should have a 

 drier soil ; and, when from a colder to a warmer, 

 a moister one, than in their native station. 



It has hitherto been regarded almost an axiom, 

 that no plant produced by cuttings ever becomes 



