Geology and Natural History. 75 
discovered and weighty evidence in s views 
He adheres to his well-known belief, now well established, that pla- 
cent belong to carpels and not to the cauline axis 8 
or to outgrowths of a leaf, whether from its edges or surface. 
Under fruits and seeds, little new matter has been added, except 
a useful synopsis of simple fruits. 
Thus far the work has dealt with Morphology and adapta- 
tions: the last part of the volume is devoted to Taxonomy. 
tion and classification, by the individual is meant the herb, shrub, 
.” “Species in biological natu- 
ral history is a chain or series of organisms of which the links or 
ments of species are: 1, community of origin; and, 2, similarity 
foundation of species.” Variation within the species is next dis- 
i us 
each other within such limits interbreed freely, while those with 
wider differences do not. Hence are recognized Varieties, or dif- 
tions, in which the differences are more st denote 
degrees of likeness or difference ; but what is the explanation of 
the likeness between species themselves ? ith the accepted 
facts respecting variation, crossing and the like, before him, the 
author adopts the theory of descent and limitation by natural 
selection, to furnish an' answer to the question Just asked. 
On page 330, the author says, “ We have supposed -.+. that 
each plant has an internal tendency or predisposition to vary In 
some directions rather than in others; from which, under natural 
selection, the actual differentiations and adaptations have pro- 
one Under this assumption and taken as a working hypothe- 
