102 SCIENCE PROGRESS. 



Turning now to those cases of metamorphosis which 

 cannot be traced to injury, we find ourselves at once con- 

 fronted with the great biological problem of the antagonistic 

 relation existing between growth and reproduction. The 

 fundamental observation illustrating this is that recorded by- 

 Linnaeus as the basis of his theory of Prolepsis, to which 

 I have already drawn attention — the observation, namely, 

 that when a tree is abundantly supplied with nourishment it 

 develops leafy shoots, whereas when transplanted to poor 

 soil, or to the narrow limits of a pot, it develops flowers. 

 This idea of the relation between deficient nourishment and 

 flowering — that is, reproduction — also occurs in Wolff's 

 writings, for he refers flowering to a vegetatio languescens et 

 evanescens. With Goethe the idea takes a somewhat 

 different form. He assumes that the foliage-leaves on the 

 lower parts of the plant are products of coarser nutritive 

 sap which, as it ascends, undergoes refining by filtration and 

 thus becomes suited for the development of the floral organs. 



On comparing the views of Linnaeus and of Goethe, we 

 observe that they differ in that the former refers meta- 

 morphosis of the leaves entirely to external, the latter 

 entirely to internal causes. We will briefly consider this 

 point. Whilst there is no doubt that external conditions 

 may induce, there is evidence to show that they do not 

 originate, metamorphosis. To return to an example already 

 cited : it is truethat the lower shootsof the potato-plant will not 

 develop into tubers unless they are covered up with earth ; 

 but this treatment does not confer upon them the capacity 

 of developing into tubers, for the shoots of other plants 

 treated in the same way do not so develop. Again, in 

 Linnaeus' observation given above, whilst it is true that a 

 certain change in the environment of a tree may hasten its 

 flowering, this change does not confer upon the tree the 

 power of flowering ; that it possesses already, and would 

 eventually manifest it even though left to grow in a rich and 

 unlimited soil. And, finally, in the case lately quoted of 

 chloranthy resulting from injury, the puncture of the insect 

 would lead to no such change were not the capacity for it 

 already inherent in the plant. 



