330 THE WORLD OF LIFE CHAP. 



a hundred feet or more above the surface, by means of forces 

 whose nature and exact mode of operation is still a mystery ; 

 while by means of the very same tissues and vessels those 

 recondite chemical processes are being carried on which 

 result in the infinitely varied products already very briefly 

 referred to. 



The living plant not only builds up its own marvellous 

 structure out of a few elements supplied to it either in a 

 gaseous or liquid state, but it also manufactures all the 

 appliances cells, vessels, fibres, etc. needful for its com- 

 plex laboratory-work in producing the innumerable by- 

 products possessing so many diverse properties useful to 

 man, but which were mostly unneeded by the remainder of 

 the animal world. 



Usually botanists as well as zoologists are satisfied to 

 describe the minute structure of the organs of plants or 

 animals, and to trace out as far as possible the changes that 

 occur during growth, without any reference to the unknown 

 and unintelligible forces at work. As Weismann has stated, 

 the fundamental question " the causes and mechanism by 

 which it comes about that they (the gemmules or physio- 

 logical units) are always in the right place and develop into 

 cells at the right time" is rarely or never touched upon. 1 

 Modern theories of heredity take for granted the essential 

 phenomena of life nutrition, assimilation, and growth. 



I find, however, that Professor Anton Kerner, in his 

 great work on The Natural History of Plants, fully recog- 

 nises this great fundamental problem, and even recurs to the 

 much derided " vital force " as the only help to a solution of 

 it. He says : 



" The phenomena observed in living protoplasm, as it grows and 

 takes definite form, cannot in their entirety be explained by the 

 assumption of a specific constitution of protoplasm for every distinct 

 kind of plant, though this hypothesis may prove useful when we 

 enquire into the origin of new species." 



Again he says : 



" In former times a special force was adduced, the force of life. 

 More recently, when many phenomena of plant-life had been success- 



1 The Germ-Plasm, p. 4. 



