﻿BOTANICAL GAZETTE 



Results and advantages. — The obvious result of the xerofotic 

 position is to decrease the amount of direct radiant energy received 

 per unit area of leaf. This reduces the harmfulness of too great 

 sunlight upon the chlorophyll, as well as reducing the transpiration 

 during the critical time of day. Its frequency is undoubtedly a 

 valuable asset to the family Leguminosae, one of the most important 

 plant families and the richest in species in the tropics. 



Fig. 6—Ipomoca Pes-caprae. jrrowinfr in the shuck-, showing leaves in spread-out 

 position; Taal Volcano, P.I., March 7, 1915. 



The assumption of the xerofotic position permits a great deal 

 more light to come through the leaf layer. This is admirably 

 shown in rigs. 3 and 4 of Leucaena glauca, taken on the same day 

 from the same spot; fig. 3 when the leaflets were in the horizontal 

 ( position; and fig. 4 three hours later, after the leaflets had assumed 

 the xerofotic position. 



Experimentation. — That this class of movements might not 

 rest solely on observation, a number of experiments were performed 

 at Los Banos, Philippine Islands, during 1913 and 1914- Screens 

 were interposed between the sun and plants of Glirichlia septum. 

 Leucaena glauca, and Mimosa pudica, whose leaflets were in the 

 xerofotic position. In every case the leaflets fell back to the 

 horizontal position. Occasionally as short a time as 5 minutes 



