272 THE INDUCTIONS OF BIOLOGY. 



aberrant parasites like the Rafflesiacece, in which the centre 

 or axis which arises from a fertilized germ becomes the im- 

 mediate producer of fertilized germs. 



In propagation ^characterized by unlikeness of the succes- 

 sive generations, there is asexual genesis with occasionally- 

 recurring sexual genesis ; in other words — agamogenesis inter- 

 rupted more or less frequently by gamogenesis. If we set out 

 with a generation of perfect males and females, then, from 

 their ova arise individuals which are neither males nor 

 females, but which produce the next generation from buds. 

 By this method of multiplication many individuals originate 

 from a single fertilized germ. The product of development is 

 organized round more than one centre or axis. The 



simplest form of heterogenesis is that seen in most uniaxial 

 plants. If, as we find ourselves obliged to do, we regard 

 each separate shoot or axis of growth as a distinct indi- 

 vidual, homogenesis is seen in those which have absolutely 

 terminal flowers; but in all other uniaxial plants, the suc- 

 cessive individuals are not represented by the series A, A, A, 



A, &c., but they are represented by the series A, B, A, B, A, 



B, &c. For in the majority of plants which were classed 

 as uniaxial (§ 50), and which may be conveniently so dis- 

 tinguished from other plants, the axis which shoots up from 

 the seed, and substantially constitutes the plant, does not 

 itself flower but gives lateral origin to flowering axes. Though 

 in ordinary uniaxial plants the fructifying apparatus appears 

 to be at the end of the primary, vertical axis; yet dissection 

 shows that, morphologically considered, each fructifying axis 

 is an offspring from the primary axis. There arises from the 

 seed a sexless individual, from which spring by gemmation 

 individuals having reproductive organs ; and from these there 

 result fertilized germs or seeds that give rise to sexless indi- 

 viduals. That is to say, gamogenesis and agamogenesis alter- 

 nate: the peculiarity being that the sexual individuals arise 

 from the sexless ones by continuous development. The 

 SalpcB show us an allied form of heterogenesis in the animal 



