265 



The third group contains A triplex vesicarium, Rhagodia Gaudichandiana, 

 and Kochia sedifolia, and these I have further subdivided into (a) Atriplex and 

 Rhagodia, (h) Kochia. All the species in this group are characterised by their 

 transpiration curves running parallel to the time axis for a considerable period 

 during the day ; that is, their transpiration rates appear to be independent of the 

 physical conditions. In the case of Atriplex and Rhagodia the transpiration rate 

 began to fall about 4 o'clock, whilst in Kochia the constant loss rate continued 

 until 8 o'clock. 



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Curve for rate of transpiration of Geijcra parviflora. 

 T, Temperature ; E, Evaporating Power ; L, Light Intensity. 



It is evident that these curves cannot be interpreted on the basis of the 

 external physical factors alone, and therefore a study was made of the anatomy 

 of the plants from a physiological point of view. On so doing it was found 

 that the transpiration loss could be correlated with the structure of the transpiring 

 shoot, and that the plants could be divided into three classes according to their 

 histological modifications, and, further, that these three classes coincided exactly 

 with those groups which were created from a physical analysis of the curves. 

 Before discussing the transpiration of the shoots in the light of their physiological 

 anatomy a brief description will be given of their structure. 



