126 HOURS WITH NATURE. 



something about the leaf* and we cannot do it 

 better than by studying that of the ashwathwa. It has 

 two parts ; the larger part is thin, broad and flat, with 

 a network of ribs and veins and terminated by a pointed 

 end : the smaller part is the stock, which is round, 

 smooth, somewhat long, and very slender causing 

 the leaf to tremble at the slightest breeze* During the 

 greater part of the year the leaf is green of varying 

 shades, The surfaces of the leaves are not continuous 

 but are iterrupted by great numbers of small openings 

 which allow air to enter into and escape from a great 

 system of interspaces which is present in all the tissues, 

 Owing to this air is constantly enterning the plant by the 

 leaves and water evaporating from them, unless when 

 the atmosphere is salurated with vapour. The air con- 

 tains carbonic acid which serves as food for the plant, 

 because the living matter of the tissues has the power 

 of decomposing it and retaining the carbon whilst the 

 oxygen is set free ; and the evaporation of the water plays 

 the part of a suction pump and helps to draw the water 

 upwards from the roots. 



We have been led to make these remarks in order 

 to show that the leaves take an important part in rais- 

 ing water in a tree. But we have yet to see how this 

 is done. It is simple enough, The living contents of 

 leaf are always thirsting for water ; so that, as soon a? 

 any cell loses water by evaporation, it sucks it up from its 

 neighbour, and this process of robbing the neighbouring 

 celJs of their aqueous contents goes on down to the very 



