THE RELATION OF SIZE AND FORM IN PLANTS 595 



These varied examples show how uniformly increase in Size is 

 accompanied by elaboration of Form. As they stand, the uniformity 

 of these results points to some definite relation between Size and 

 Form. The degree of constancy shown in the ratios is not a matter 

 of chance, whatever may be its physiological significance. On the 

 other hand the results have not been found referable to any external 

 agency : they are certainly not dependent on the influence of appen- 

 dages, for in three of the instances quoted there are none. The 

 degree of constancy in the ratios in the last column is not exact : 

 nevertheless it suggests some inner influence that controls elaboration 

 of form in accordance with increase of size in each of the several cases. 



Problem of Supply to Distal Buds of Vascular Plants. 



In plants of advanced but primary organisation, obconical growth leads 

 towards enlargement of the distal bud. This is often associated with a 

 marked restriction, diminution, or even absence of branching, as in many 

 Ferns and Palms (Fig. 446). In these, as development proceeds, the 

 axis may expand to great bulk. Thus, in Amphicosmia, a well-grown 



Fig. 450. 



Apex of stem of a large plant of Amphicosmia Walkerae, shown natural size : 

 with the arrangement of the leaves in trimerous whorls upon the flattened apical 

 plateau. 



Fern, but not of the largest size, the flattened apex, which may bear 

 four cycles of leaf-primordia upon it, was found to be fully four centi- 

 metres in diameter (Fig. 450). Its bulk is enormous as compared with 

 the buds of forest trees, such as the Beech (Fig. 451), where the growing 



