78 MORPHOLOGICAL DEVELOPMENT. 



may naturally expect it to begin moulding itself round an 

 axis of its own: a foliar organ will be replaced by an axial 

 organ. And this result will be especially liable to occur, 

 when the growth of the axis has been previously undergoing 

 that arrest which leads to the formation of a flower; that is 

 when, from defect of materials, the terminal process has 

 almost ceased to increase, and when some concurrence of 

 favourable causes brings a sudden access of sap which reaches 

 the lateral processes before it reaches the terminal process.* 



198. The general conclusion to which these various lines 

 of evidence converge, is, then, that the shoot of a flowering 

 plant is an aggregate of the third degree of composition. 

 Taking as aggregates of the first order, those small portions 

 of protoplasm which ordinarily assume the forms under 

 which they are known as cells ; and considering as aggregates 

 of the second order, those assemblages of such cells which, 

 in the lower cryptogams, compose the various kinds of thal- 

 lus; then that structure, common to the higher cryptogams 

 and to phaenogams, in which we find a series of such groups 

 of cells bound up into a continuous whole, must be regarded 

 as an aggregate of the third order. The inference drawn 

 from analysis, and verified by a synthesis which corresponds 

 in a remarkable manner with the facts, is that those com- 

 pound parts which, in Monocotyledons and Dicotyledons are 

 called axes, have really arisen by integration of such simple 

 parts as in lower plants are called fronds. Here, on a higher 



* It is objected that these transformations should be much commoner than 

 they are, were they caused solely by the variations of nutrition described. 

 The reply is that they are comparatively rare in uncultivated plants, where 

 such variations are not frequent. The occurrence of them is chiefly among 

 cultivated plants which, being artificially manured, are specially liable to 

 immense accessions of nutriment, caused now by sudden supplies of fertilizing 

 matters, and now by sudden arrival of the roots at such matters already 

 deposited in the soil. It is to these great chanffes of nutrition, especially apt 

 to take place in gardens, that these monstrosities are ascribed ; and it seems 

 to me that they are as frequent as may be expected. 



