XIV] 



AMOUNTS OF WATER TRANSPIRED 



141 



Von Hohnel, who estimated that the proportion of water 

 transpired in equal times by the same dry weight of leaf 

 substance was on the average as follows : 



Whence we see that the Pines, Spruce and Silver Fir 

 transpire very much less water than any deciduous tree 

 examined. As the result of prolonged investigations it 

 was concluded that where the water-supply is sparse, the 

 Conifers transpire about one-tenth as much as do the de- 

 ciduous Dicotyledons, but where there is plenty of water 

 the proportion may rise to one-sixth or one-seventh as 

 much. 



Now it is interesting to note that there is one Conifer, 

 viz. the Larch also with narrow leaves, which for a 

 time may transpire as vigorously as do the most active of 

 the Dicotyledons referred to, e.g. the Ash (which, with the 

 Birch, Lime, Alder and Pyrus torminalis, is one of the 

 most powerfully transpiring trees in Europe), and at first 

 sight it appears as if we had here a serious contradiction, 

 for the Larch is an Alpine Conifer of the highest altitudes. 

 Such is not the case, however. The Larch simply faces 

 the conditions with a different equipment of adaptation : 

 its narrow and delicate leaves are deciduous, and are 



