294 PHYSIOLOGICAL DEVELOPMENT. 



holding the assimilating organs under ordinary and extraor- 

 dinary strains; and in these assimilating organs we see 

 elaborate appliances for yielding to the stem and roots the 

 materials enabling them to fulfil their offices. As a con- 

 sequence of which greater integration accompanying the 

 greater differentiation, there is ability to maintain life over 

 an immense period under marked vicissitudes. 



Even more conspicuously exemplified in Phaenogams, is 

 that physiological integration which holds together the func- 

 tions not of the individual only but of the species as a whole. 

 The organs of reproduction, both in their relations to other 

 parts of the individual bearing them and in their relations to 

 corresponding parts of other individuals, show us a kind of 

 integration conducing to the better preservation of the race; 

 as those already specified conduce to the better preservation of 

 the individual. In the first place, this greater co-ordination 

 of functions just described, itself enables Phaenogams to be- 

 queath to the germs they cast off, stores of nutriment, pro- 

 tective envelopes, and more or less of organization : so giving 

 them greater chances of rooting themselves. In the second 

 place, certain differentiations among the parts of fructifica- 

 tion, the meaning of which Mr. Darwin has so admirably ex- 

 plained, give to the individuals of the species a kind of inte- 

 gration that makes possible a mutual aid in the production of 

 vigorous offspring. And it is interesting to observe how, in 

 that dimorphism by which in some cases this mutual aid is 

 made more efficient, the greater degree of integration is 

 dependent on the greater degree of differentiation — not simply 

 differentiation of the fructifying organs from other parts of 

 the plant bearing them, but differentiation of these fructify- 

 ing organs from the homologous organs of neighbouring indi- 

 viduals of the same race. Another form of this 

 co-ordination of functions which conduces to the maintenance 

 of the species, may be here named — partly for its intrinsic 

 interest. I refer to the strange processes of multiplication 

 occurring in the genus Bryophyllum. It is well known that 



