PHYSIOLOGICAL INTEGRATION IN PLANTS. 277 



dinary strains ; aud in these assimilating organs we set 

 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 functions 

 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 Icind 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, pi'o- 

 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 fructification, 

 the meaning of which Mr. Darwin has so admirably explained, 

 give to the individuals of the species a kind of integration 

 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 fructifying 

 organs from the homologous organs of neighbouring indi- 

 viduals of the same race. Another form of this 

 co-ordination of functions that conduces to the maintenance of 

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

 interest. I refer to the strange processes of multiplication 

 that occur in the genus Bryophyllum. It is well knovi'n that 

 the succulent leaves of B. calycinum, borne on foot-stalks 



