TYPES OF DTMORPTTir RPECTATJZATION. ' 41 



Goebol consideis Wiesner's (Icliuitioii of anis()j)hylly too narrow, 

 and would inchulo casos whore the leaves on th(^ under side of the 

 shoot are smaller than tliose on the up])er side, as the following 

 statements will show: 



By anipophylly we mean that leaves of a different size and of different qnality 

 appear on the different sides of pla<iiotropous shoots; (he leaves which stand upon 

 the upper side are usually smaller than those upon the under side, but the converse 

 is also sometimes the case. * * * All the examples have this in common, that the 

 anisophylly occurs exclusively upon plagiotropous shoots and that it is a character oj 

 adaptation which has an evident relation to the direction of the shoot and especially 

 to its position with regard to light., * * * Herbert Spencer in 1805 first directed 

 attention to the anisophylly of lateral shoots in plants with decussate leaves, as well 

 as to the connection of the anisophylly of higher plants with external factors, espe- 

 cially with light. * * * The term has come to us from Wiesner, although his 

 definition, which is as follows, is too narrow: "I mean by anisophylly that the leaves 

 lying upon the upper side of prone shoots have smaller dimensions than those upon 

 the under side, whilst the lateral ones are intermediate." We know, however, that 

 the leaves on the under side may be smaller, as is the case in the foliose Jungerman- 

 nieae and in Lympodium complanatum. ' 



An excellent example of anisophylly is found in the common 

 paper mulberry (Broussonetia), as shown in figure 18. Indeed, 

 Broussonetia may be said to combine two phenomena, for in addi- 

 tion to the distinctly smaller size of the leaves that arise from the 

 upper side of the branch there is a wide range of diversity in the 

 forms of the leaves, which constitutes heterophylly. 



Anisophylly is to be considered as a physiological phenomenon, 

 rather than morphological. The inequalities in the size of the leaves 

 are supposed by Wiesner and Goebel to arise by direct accommoda- 

 tion to the position in which they happen to be formed. An accident 

 to a tree that changes the position or exposure of a growing shoot 

 affects the condition of anisophylly by rendering the leaves more or 

 less unequal than they otherwise would have been. Yet the in- 

 terpretations that have been placed upon anisophylly do not seem to 

 be altogether consistent. In some cases it is considered that the 

 larger size of some of the leaves is connected with better exposure 

 to liidit, but in Broussonetia it would seem that the light must be 

 supposed to restrict growth, for the smaller leaves are produced from 

 the upper side of the branch. Some writers look upon the small 

 leaves as specially adapted to fit in among the large ones and thus 

 utihze all the surface of exposure. In this view Broussonetia would 

 seem to have overshot the mark. Figure 18 indicates that much 



1 Goebel, K. Organography of Plants, Especially of the Archegoniatte and Spermaphyta, pt. 1, 1900, 

 pp. 99-100. 



Additional cases of anisophylly in tropical plants from the Malay region have been reported by Hein- 

 richer in a paper that concludes with a list of several other papers on the subject. (See ITeinricher, E. 

 Beitraege zur Kenntnis der Anisophyllie, Annales du Jardin Botanique de Buitenzorg, sup. 3, pt. 2, 

 1910, pp. 049-0(14, and pi. 25. 

 221 



