/ 



184 



On the Theory of Yegetation. 



mist 



up and watered the face of the earth;" as the 



case is still in some eastern countries. 



I 



will close this letter, Sir, by relating an experiment 



I have lately made to ascertain the evaporation or perspir 



damp 



unconnected with 



tion of plants, growing in a 

 earth. 



On the 9th of May I weighed two potatoes, on which the 



young shoots just began to appear. I placed them both in 



on a dry piece of timber 



dark corner of the cellar 



I 



ghed them both 



the 28th of the 



munth. and on 



the 11th of June. The result of the whole follows 



The largest weighed. 



t3 



oz. 



May 



9th, 1 



May 28 

 June 11 





 1 



18 



13 



12 



grs. 



19 





 11 



The smallest weighed. 



loss of weight in 19 days 



in 14 days 



loss of 



do. 



pwt. grs. 



5 19 

 13 



May 



May 2S 

 June 11 



9 th 



OZ. 



1 





 







19 



19 



grs, 



8 

 19 



4 



The 



loss of weight in 19 day 



do. in 14 dayj 



loss of 



13 

 15 



shoots in the meen time had grown to the leno-th of 



two and three inches 



0% weighed 1 penny weisht 7 



Those of the largest, when broken 



g 



18 grains; so the actual diminut 



33 

 28 



day 



6 penny weight 8 grains of the 



4 



those of the smallest 

 of the potatoes in 



and 



5 



of the 



The perspiration of plants is ascribed to the _„^.„„ 

 the air in the tracheje, in conseouence of being heeted 



expan 



Q of 

 The 



absorption 



t 



