AND INSKNSIRLK P?:RSPIR ATFON. ^f 



some of the secreted juices, which in that phmt are ex- 

 tremely acid and astringent. The sap ol" the Suo;ar 

 Maple, Acer saccharinum, has no taste, though accoiding 

 to Du Hamei every 2!00ib. of it will afford 101b. of 

 sugar. Probtbly, as he remarks, it is not collected 

 without an admixture of secreted fluids. 



As soon as the leaves expand, insensible perspiration 

 takes place very copiously, chiefl\ from those oigans, 

 but also in some degree from the bark of the young stem 

 or branches. The liquor perspired becomes sensible 

 to us by being collected from a branch introduced into 

 any sufficiently capacious glass vessel, and proves, for 

 the most part, a clear watery liquor like the sap, and 

 subject !o similar chemical changes. It is observed to 

 be uniform in all plants, or nearly so, as well as the sap, 

 except where odorous secretions transude along with it. 

 Still there must be a very essential difference between 

 the original sap of any plant and its perspiration, the lat- 

 ter no longer retaining the rudiments of those fine secre- 

 tions which are elaborated from the former ; but that 

 diflTerence eludes our senses as well as our chemistry. 

 Tlie perspiration of some plants is prodigiously great. 

 The large Annual Sunflower, Hdianthus annuus, Ger- 

 arde Emac. 751. f. I, according to Dr. Hales, perspires 

 about 17 times as fast as the ordinary insensible perspi- 

 ration of the human skin. But of all plants upon record 

 I think the Cornelian Cherry, Cormis mascula, is most 

 excessive in this respect. The quanthy of fluid which 

 evaporates from its leaves in the course of 24 hours, is. 

 said to be nearly equal to twice the weight of the whole 

 shrub, Du Hamel PIujs. des Arbres, v, L 145. 



