72 MORPHOLOGICAL DEVELOPMENT. 



bils by Phssnogams, ceases to be so surprising when we find 

 it to be habitual among the inferior Acrogens ; and when we 

 see that it is but a repetition, on a higher stage, of that self- 

 detachment which is common among proliferously-produced 

 fronds. Nor are we any longer without a solution of that 

 transformation of foliar organs into axial organs, which 

 not uncommonly takes place. How this last irregularity 

 of development is to be accounted for, we will here pause a 

 moment to consider. Let us first glance at our data. 



Tho form of every organism, we have seen, must depend 

 on the structures of its physiological units. Any group of 

 such physiological units will tend to arrange itself into the 

 complete organism, if it is uncontrolled and placed in fit 

 conditions. Hence the development of fertilized germs ; and 

 hence the development of those self-detached cells which 

 characterize some plants. Conversely, physiological units 

 which form a small group involved in a larger group, and are 

 subject to all the forces of the larger group; will become sub- 

 ordinate in their structural arrangements to the larger group 

 — will be co-ordinated into a part of the major whole, in- 

 stead of co-ordinating themselves into a minor whole. This 

 antithesis will be clearly understood on remembering how, 

 on the one hand, a smaU. detached part of a hydra soon 

 moulds itself into the shape of an entire hydra ; and how, 

 on the other hand, the cellular mass that buds out in place 

 of a lobster's lost claw, gradually assimies the form of a claw 

 — has its parts so moulded as to complete the structure of 

 the organism : a result which we cannot but ascribe to the 

 forces which the rest of the organism exerts upon it. Con- 

 seqviently, among plants, we may expect that whether any 

 portion of protoplasm moulds itself into the typical form 

 around an axis of its own, or is moulded into a part subor- 

 dinate to another axis, will depend on the relative mass of 

 its physiological units^ — the accumulation of them that has 

 taken place before the assimiption of any structural arrange- 

 ment. A few illustrations will make clear the validity of 



