4 GENERAL DIFFERENTIATION OF THE PLANT-BODY 



involved in changes of a fixed character and are subjected to the influences 

 exercised upon them by the outer world ; it has, in other words, to do 

 with that part of life-phenomena which finds expression in the external 

 configuration. 



The life-phenomena exhibited by plants are usually regarded as 

 within the province of physiology, and the distinction which is drawn 

 between physiology and morphology is, that physiology has to do with 

 the functions of the organs of plants, whilst morphology takes no heed 

 of these, but is rather a comparative and phylogenetic study. Sachs \ 

 for example, says : ' The parts of plants which we usually speak of as 

 their organs, and which vary so much in form and serve such different 

 physiological purposes, may be considered scientifically from two points of 

 view. We may look at them as adapted by their form and structure 

 for the carrying on of certain physiological processes, and in this case 

 we regard them as agents for work as organs. Such considerations 

 are a part of physiology. On the other hand we may look at them 

 apart altogether from these functions, and seek to determine where and 

 how they arise, and in what relationships, both of space and time, the 

 origin and the growth of one member 2 stand to those of another. This 

 method falls within the province of morphology.' 



A distinction of this kind is however, as Sachs expressly states, 

 artificial and imperfect, and it may only be maintained so long as it does 

 good service. As a matter of fact, it has finally led to one-sidedness, 

 and its outcome has not infrequently been empty theorizing. In nature 

 the form and function of an organ stand in the most intimate relation 

 to each other ; one is caused by the other. I take exactly the same 

 view as is expressed by Herbert Spencer 3 , whose work is far too little 

 valued by botanists. He says : ' Everywhere structures in great measure 

 determine functions ; and everywhere functions are incessantly modifying 

 structures. In nature, the two are inseparable co-operators ; and science 

 can give no true interpretation of nature, without keeping their co-operation 

 constantly in view. An account of organic evolution, in its more special 

 aspects, must be essentially an account of the inter-actions of structures 

 and functions. . . .' 



The title of the present volume is based upon the idea so aptly 



1 Sachs, Lehrb. der Botanik, ed. 4, p. 151. I cite this because it expresses clearly a conception 

 that is even now widely prevalent. It is well known that Sachs himself changed his view. See 

 for this his 'Lectures on Physiology,' and his ' Gesammelte Abhandlungen.' 



- The word member (Glied) is the common term for an external organ (Organ) of plants 

 and animals. There are no members which are not organs, leaving out of consideration of course 

 cases of arrest. I am at a loss then to understand such a sentence as this : ' The morphology 

 of plants knows no organs (Organe) but only members (Glieder) of the plant-body.' (Strasburger, 

 Lehrb. ed. 2, p. 7.) 



s Herbert Spencer, Principles of Biology, vol. ii. p. 4. 



