10 THE DATE PALM. 



surface or the other. The last two characters are common in 

 many other plants, the leaves of which stand more or less 

 vertical and which present about as many of the backs as the 

 faces of the leaves towards the sun. 



The leaflets of the date palm are folded once lengthwise, 

 the two edges being turned upwards (see illustration No. 12, 

 figure II, (a), opposite). At the base of the leaflet where it joins 

 the main axis the fold is fixed, and is nearly complete, i.e., the 

 two edges of the leaflet almost meet each other. When the 

 palm has a plentiful water-supply and other conditions are 

 favourable, each leaflet beyond its basal part is unfolded to 

 expose as large a surface area as possible to the sun, thus 

 allowing the chlorophyll to do its maximum work and to give 

 the stomata on both the face and back of the leaflet the freest 

 action (see illustration No. 12, figure II, opposite), but when 

 there is a scarcity of water the leaflet folds itself more or less 

 tightly along its whole length, and the two halves of the face 

 of the leaflet come together, thus protecting that surface of the 

 leaflet from the dry winds and reducing the amount of moisture 

 transpired from the plant (see illustration No. 12, figure I, 

 opposite). At the same time the leaflets tend to swing round 

 and crowd more together, thus sheltering each other from the 

 dry winds. These closing movements are caused by the contrac- 

 tion of a small pad of a yellowish tissue called a " pulvinus " 

 situated at the base of each leaflet. 



With a fair water-supply and other normal conditions there 

 seems to be no marked diurnal change in the degree of folding 

 of the leaflets. 



5. The stem is surmounted by a terminal bud which continues 

 to produce fresh young leaves throughout the life 



Buds. ' 



of the palm. If these young leaves are taken 

 carefully apart from the stem, a very poorly developed bud, 

 which usually looks like a mere pustule, is generally to be found 

 in the axil of each leaf, i.e., directly at the base of the main 

 axis of the leaf, in the upper angle formed by that axis and the 

 stem. By far the most of these tiny axillary buds never develop 



