248 



The rate of growth of each leaf increases from the beginning 

 until it is about half the mature size and then falls. The highest 

 daily rates observed in Boehmeria and Alchornea, 44 mm. and 

 2"9 mm. respectively, are the most rapid found in any of the 14 

 forms that I measured, excepting in the tree-ferns. These figures 

 contrast markedly with the rates of 107 mm. per day for the 

 banana and 41 mm. for Amherstia. From eye observations of 

 growth in a number of other species I should say that the above 

 rates are but slightly if at all exceeded in any of the forms not 

 measured, with the possible exception of Brunellia comocladifolia, 

 Humb. & Bonpl. 



Clethra tinifolia, Sw. is a characteristic forest tree with leaves 

 10 to 15 cm. long by 4 to 7 cm. wide. It is almost completely 

 deciduous and remains for about six weeks in this condition, 

 new leaves beginning to appear about the middle of March. The 

 following measurements were made on newly unfolding leaves on 

 a tree which was almost bare of old foliage. 



Other trees in the Cinchona region which shed their foliage 

 completely in the late winter and renew it during March and 

 April are Viburnum glabratum, H. B. K., V. villosum, Sw. and 

 Rhamnus sphaerosperma, Sw. Although I have made no exact 

 measurements on these forms yet almost daily observation of 

 certain trees during the time of leaf-growth makes certain that 

 their rate is not at all more rapid than that of Clethra. 



Tovomita havetioides, Griseb. is a small tree with leaves 8 to 11 

 cm. long by 4 to 6 cm. wide. The twigs are stout and the 

 leaves leathery, about 3 mm. thick and possessing a latex, 

 features which give the tree an aspect of being slow in growth. 

 The measurements include the short petiole. 1 



Date. A. Size. Rate. B. Size. Rate. 



Mar. 20 

 Apr. 2 

 Apr. 18 

 May II 



44 



60 



80 



109 



1-23 

 1-25 



I'26 



41 

 52 



66 



88 



•84 

 •87 

 '95 



Elongation here proceeds with a greater uniformity during the 

 development of the leaf than is the case in any thin leaved forms 

 measured, but the rate is not strikingly slower than in Clethra. 



The slowest rates of growth observed were for the leaves of 

 Pilea nigresccns, Urb., one of the commonest terrestrial herbaceous 



