ARTICLES 75 



tion values are considered in relation to water, the loss of 

 water per ioo sq. cm. of surface being taken as ioo : 



Table VI 

 Relative transpiration per hour per ioo sq. cm. of surface 



These results corroborate the former and show that the loss 

 of water from succulent plants is considerably in excess of 

 that from certain mesophytes. It should be mentioned that 

 in one respect the results shown in the last table are not strictly 

 comparable, for whereas a shoot of Salicornia was employed, 

 in the case of Sedum and Vicia the leaves were detached. It 

 is not unlikely that these leaves transpired at a rate greater 

 than would have been the case if they had not been removed 

 from their respective shoots. But this does not militate 

 against the sense of the results, for it makes the difference 

 between the two non-halophytes — Sedum and Vicia — and 

 Salicornia still greater. 



ABSORPTION OF WATER BY THE AERIAL PARTS 



In view of the saline nature of the soil of salt marshes, this 

 high transpiration is surprising, and the observer is naturally 

 led to consider whether the rainfall is sufficient to provide 

 the roots with the requisite amount of water. 1 In fact, in some 

 years the rainfall during the growing season may be so small 2 

 that sources of supply other than by the absorption of fresh 

 water from the soil must be sought. 



For the reason that in Salicornia, provided the plants are 



1 It may be remarked, that for the purposes of investigations such as these, the 

 ordinary rainfall records are of but little value ; for ecological work on marshes 

 which are inundated by the tides, hourly records are desirable, for it is obvious that 

 rain which falls immediately before or during the period of high tide is valueless 

 in providing the soil with fresh water. At Erquy such hourly observations were 

 impossible. For the present purpose it may be assumed that the whole of the 

 rain which fell during the vegetative season was available for the plants. 



1 The following are records of the rain which fell on the Bouche d'Erquy during 

 the vegetative season (April 1 to September 12) in the specified years : 1906, 

 3*69 in. ; 1907, 5*06 in. ; 1908, 4*38 in. ; and 1909, IC48 in. 



