112 



RELATIONSHIPS OF SYMMETRY 



indicated in this species. The plant does not form a flat branch-system 

 because the smaller leaves produce axillary shoots ; this is the case at 

 least in plants cultivated in plant-houses, but it is possible that in the 

 shade of woods of the natural habitat the plagiotropy and anisophylly 

 may be more marked 1 . In any case these characters are not so fixed 

 here as they are in C. inaequilateralis. 



3. Acanthaceae. I take the genus Goldfussia as an example, and 

 Fig. 66 is a diagram of the positions in Goldfussia glomerata. The 

 leaves are in this species decussate, but the leaf-pairs are subsequently 

 displaced so that they do not cross at right angles ; the divergence 

 between the larger leaves becomes greater than 90 and they appear 

 displaced to the sides, whilst the divergence of the smaller leaves becomes 

 less than 90. The axillary buds are shown in transverse section in the 

 diagram. Each of them begins with two lateral leaves of which one is 



FIG. 66. Goldfussia glomerata. Diagram. The leaves of the chief shoot are seen in surface view, those of 

 the axillary shoot in transverse section. 



commonly smaller than the other, and they are followed by a second leaf- 

 pair in which the leaf next the mother-axis is the smaller. This position 

 is of importance, as I have elsewhere pointed out, because it shows that 

 the anisophylly does not stand, as was formerly supposed, in direct 

 causal relationship to gravity. It is true that in the first pair of leaves 

 the leaf which is towards the inner side, when one regards the chief 

 shoot as being inclined or horizontal, is the larger, but in the following 

 pair of leaves, in which the disposition in relation to the mother-shoot 

 is the critical one, this is not the case, but the larger leaf is always 

 that which is on the side of the bract and away from the mother-shoot, 

 no matter whether the bud lies towards the upper side or towards 



1 The differences are often somewhat greater than I have stated and they would seem to be variable. 

 In dried specimens in the herbarium I have found the small leaves only 1-2 cm. long and large ones 

 4-6 cm. 



