S6 MORPIIOLOGICAL DEVELOPMENT. 



flowers are brougtt into a cluster ; as tKey are in the co-ws- 

 lip. On contemplating a cloTer-flower, in which thia 

 clusteriag has been carried so far as to produce a com- 

 pact head ; and on considering what must happen if, by a 

 further arrest of axial development, the foot-stalks of the 

 fl Drets disappear ; it will be seen that there must result a 

 crowd of flowers, seated close together on the end of the axis. 

 And if, at the same time^ the internodes of the upper stem- 

 leaves also remain undeveloped, these stem-leaves will be 

 grouped into a common calyx or involucre : we shall have a 

 composite flower, such as the thistle. Hence, to modifications 

 in the developments of foliar organs, have to be added modi- 

 fications in the developments of axial organs. Comparison? 

 disclose the gradations through which axes, like their append- 

 ages, pass into all varieties of size, proportion, and structure. 

 A.nd we learn that the occurrence of these two kinds of 

 metamorphosis, in all conceivable degrees and combinations, 

 furnishes us with a proximate interpretation of morpho- 

 logical composition in Phsenogams. 



I say a proximate interpretation, because there remain 

 to be solved certain deeper problems ; one of which at once 

 presents itself to be dealt with under the present head. 

 Leaves, petals, stamens, &c., being shown to be homologous 

 foliar organs ; and the part to which they are attached, 

 proving to be an indefinitely-extended axis of growth, or 

 axial organ ; we are met by the questions, — ^What is a foliar 

 organ ? and What is an axial organ ? The morphological com- 

 position of a Phasnogam is undetermined, so long as we can- 

 not say to what lower structures leaves and shoots are homo- 

 logous ; and how this integration of them originates. To 

 these questions let us now address ourselves. 



§ 190-1. Already, in § 78, reference has been made to the 

 occasional development of foliar organs into axial organs : 

 the special case there described, being that of a fox-glove, 

 in which some of the sepals were replaced by flower-buds, 



