260 PLANT PHYSIOLOGY 



new individuals.* So far, individuals thus produced have 

 not developed to maturity, though this may be expected to 

 be attained. There is, however, an essential difference be- 

 tween individuals produced on the one hand by non-sexual 

 means, by natural parthenogenesis, and from sexual cells 

 artificially stimulated, and on the other hand by sexual 

 means the fusion of two cells. In the latter case, the one 

 cell absorbs not only simple inorganic compounds, but also 

 all the complex organic compounds contained in the other 

 sexual element ; the structure as well as the substance of the 

 two cells unites ; two sets of organs are combined into one ; 

 nucleus fuses with nucleus, cytoplasm with cytoplasm; 

 the individual characters of the two cells are combined in 

 the new individual. We see, then, that fertilization is more 

 than stimulation ; it is union. f In this union of structure, 

 organs, and characters, although these are composed of 

 chemical compounds, the definite arrangement of the parts 

 in the sexual elements is as essential as the composition of 

 the parts. The result in the new individual will vary with 

 the arrangement of the parts in each sexual element. In 

 other words, there is not only a chemical basis to fertiliza- 

 tion; there is also a mechanical. Fertilization cannot be 

 complete and perfect without both chemical and mechanical 

 effects. What the significance, and what the relative im- 

 portance, of the chemical and mechanical factors in fertili- 

 zation may be is now the subject of hypothesis and experi- 

 ment. The matter is far from settlement. 



That there are advantages in a mode of reproduction 

 which unites chemical and mechanical effects, and in develop- 

 ment which follows only after these are produced, would 

 seem to be indicated by the development of sexual repro- 

 duction by so many different types of organisms. If non- 



* Loeb. J. Artificial production of normal larva? from the unfertilized 

 eggs of the Sea Urchin (Arbacia). Amer. Journ. Physiology, vol. III., 

 1900. Experiments on artificial parthenogenesis in Annelids (Chaetop- 

 terus). Ibid. vol. IV., 1901. Nature of the process of fertilization. Ibid. 

 vol. IV., 1901. Matthews, A. P. Artificial parthenogenesis produced by 

 mechanical agitation. Amer. Journ. Physiol., vol. VI., 1901. 



t Strasburger, E. f ber Befruchtung. Bot. Zeitung, 1901. Boveri, Th. 

 Das Problem der Befruchtung. Jena, 1902. 



