THEOBY OE THE GROWTH OF CUTTIK'GS. 407 



end, every one of the cuttings is capable of developing into a new 

 individual : such, an individualized portion of a branch is called by 

 Vochting a Lebenseinheit or "Life-unit.'''' At the point where the 

 knife divides the branch it separates a mass of similar cells into 

 two sets, viz. cells which form part of the base of the upper life- 

 unit, and which therefore form roots, and others which belong to 

 the apex of the lower unit, and which develop into buds. The con- 

 clusion which Vochting arrives at as to this simple form of growth 

 is thus given* : — "A living vegetative cell which is capable of 

 growth has not a specific and unalterable function." " The func- 

 tion assumed by a cell depends on the morphological position 

 which it occupies in the life-unit, as the most important con- 

 dition." 



The second class of cuttings are those which already possess 

 " Anlagen" of two kinds — that is, buds and rudimentary roots. 

 Here the same relations hold good. The buds near the apex of 

 the life-unit develop rather than any others, and the root-rudi- 

 ments near the base develop rather than those near the apex ; 

 and this takes place in great measure independently of the posi- 

 tion with regard to gravitation occupied by the life-unit. 



Vochting gives this lawf: — "When there are a number of 

 rudiments of equal strength and morphological rank, the energy 

 of development of the individual rudiments will depend (as the 

 chief condition) on their morphological position in the life-unit." 



From a very large number of experiments, including both 

 classes of cuttings, Vochting concludes that there is an innate 

 hereditary tendency i in plants which leads to the production 

 of roots at the basal and branches at the apical end of the life- 

 unit. Besides this innate tendency, the external forces, gravita- 

 tion and light, have an influence on the development of organs. 

 Vochting § gives two laws formulating his conclusions as to the 

 action of the external forces, the chief point being that the ex- 

 ternal forces are of secondary importance in comparison to the 

 innate growth-tendency. In summing up this part of the question, 



* ' Organbildung,' p. 241. 



f hoc. cit. p. 241. His second law about rudiments of unequal strength I 

 have omitted. 



\ Vochting's term " morphological force " seems to me a useful one to express 

 the innate tendency to the production of organs in morphologically determined 

 positions. 



§ Ibid, p 243. 



