256 METAMORPHOSIS 



mode of life of an organism. We have only one act of releasing and one reaction 

 in a rifle, whilst in an organism we have numberless liberations of energy and 

 all sorts of reactions. We have a further more important difference to note, 

 viz. that one of the chief activities of an organic machine lies in its special 

 structure, its development and its reproduction, while we have still to find a machine 

 which can grow and reproduce. Finally, we know that the machine works to 

 achieve a certain end, being constructed for that very purpose, but we cannot 

 do more than form the vaguest guesses as to the purpose for which the organism 

 works. 



To sum up ; the causes of life are as yet entirely unsolved, we are ignorant 

 both as to the materials and the forces which give to living things their charac- 

 teristics ; just as little are we able to prove that other materials and other forces 

 operate in the organisms than in the non-living world. Our position with 

 regard to biological research may be permitted to rest with this expression of 

 our ignorance, since the enunciation of hypotheses on questions so general as 

 these would only too easily do injury to Natural Science. He who believes that 

 the organic world is nothing more than a collection of complicated chemical and 

 physical processes can only do so by shutting his eyes to such phenomena as 

 cannot be fitted into his theory ; he who, on the contrary, once admits that 

 the vital characteristics of the organism begin where physics and chemistry end, 

 is content to abandon altogether the toilsome path of exact investigation, and 

 aim merely at collecting the most readily accessible results of speculation at 

 his study table. As to the possibility of reaching an explanation of vital 

 phenomena the following works dealing with the subject may be consulted : 

 ALBRECHT (1901), BUTSCHLI (1901), CLAUSSEN (1901), DRIESCH (1901, [1905]), 

 HERTWIG (1897-8 [and 1905]), NAGELI (1860), REINKE (1901), WOLFF (1902). 

 [There can be no doubt, however, that physico-chemical experimental investi- 

 gation and not philosophical speculation has been the chief means of advancing 

 the science of plant physiology.] 



From the examples considered above we can readily appreciate the kind 

 of questions we have to study in the lectures yet to follow. In the present 

 lecture we need only attempt to justify the allotment of a complete section 

 of physiology to the discussion of the ' form ' of the plant and to show that this 

 question of ' form ' may be contrasted in a certain sense with ' material ' and 

 with ' energy'. If we study the introduction to SACHS'S famous memoir, ' Ueber 

 Stoff und Form ' ( 1880), it would appear as though this statement were to a certain 

 extent subject to criticism. SACHS says, ' Plant morphology often suffers the 

 misfortune of being considered from the point of view of form without any 

 reference to its material characteristics '. * A survey of the material character- 

 istics of organs ' is, however, absolutely necessary ' since it is in these only that 

 the causes of their form are to be sought for\ ' Just as the form of a drop of water 

 or of a crystal is the result of the action of certain forces which bring the 

 material in question under the influence of its surroundings, so also the organic 

 form can only be the outward result of forces which transport those materials which 

 make themselves apparent in the plant substance.' 



Valuable as are the opinions which SACHS has expressed in this treatise on 

 the subject of ' causal morphology ', we are nevertheless unable to agree entirely 

 with the sentiments expressed in the sentences quoted. We cannot find that 

 SACHS, or indeed any other author, has succeeded in referring the form of an 

 organ to its material characteristics, and, keeping before our eyes the phenomena 

 of non-living nature, we must confess that it is not probable that anything of 

 this kind is ever likely to be established. Numerous chemical compounds have 

 characteristic crystalline forms, and often these forms serve for the diagnosis 

 of different bodies. Still the same form may be possessed by different materials 

 and it would be in the highest degree dangerous to refer the leaf form, for 

 example, to one special but as yet unknown material, and still more dangerous 



