298 MARGARET S.JARVIS 



correlated with a lesser ability to maintain leaf water content under these 

 conditions. Measurements of transpiration rate were concurrently made, 

 in an attempt to distinguish maintenance of leaf turgor by increased water 

 uptake from that by decreased water loss. 



350 



TIME IN DAYS (JUNE 1960) 



Fig. 4. Thelycrania sauguinea. The effect of soil moisture tension on the rate of increase 

 of total leaf length. (1-18 June i960.) The container number (i, 2 or 3) and the number 

 of the plant in the container (i, 2 or 3) are at the ends of the curves. Soil moisture 

 tensions for container i are sho wit beside corresponding points of curve 1 3 ; similarly 

 for container 2, by 23; and for container 3, by 33. W: see Fig. 2. 



Methods (a) Leaf water content. This was expressed in terms of leaf water 

 deficit (LWD), defined as the percentage reduction in leaf water content 

 below that at full turgor; a concept introduced by Stocker (1929) and 

 since widely used. The leaves were cut from the plant and weighed im- 



