Thermostasy of Growth of the Date Pair 
Plate 4 
Above arrow, longitudinal section through the heart of the date palm shown in Plate 2; in front of 
arrow, horizontal section of half of palm 
Print mounted on square ruled paper, ordinates 1-17, abscissa a-k 
6 to 6.5 e to e 7, growth center from which group of leaves has sprung by basipetal elongation 
6.5 to 10, with bases e to e 7, longitudinal section of group of very young leaves. They are pushed 
upward by growth made wholly within the bud 
6.5 to 11.3, breadth d 1 to/, longitudinal section of bases of group of leaves 4 or 5 feet high, with 
pinnae still unexpanded, cut tops seen at c 5 to d 3, also in Plate 2 above A. These are making 
their most rapid growth 
6 to 13, breadth c 5 to g, longitudinal section of bases of older leaves, still making active growth. 
5 to 6.5, breadth d to/ 5, very tender, white brittle meristem, giving quick starch reaction. This 
is the “heart” of the palm that is sometimes eaten. It is at once the growth cap of the trunk and 
the source of supply of all leaves still making basipetal elongation 
2.4 to 6.8, opposite diagonal line showing base of longitudinal section of trunk. In front is the 
horizontal section of the stump, also showing active starch reaction 
