The Morphology of Angiosperms. 203 
phylogenetic value is discussed later in Chap. XV. which is in fact 
the conclusion of the book so far as Professors Coulter and 
Chamberlain are concerned. It will be more convenient here to 
treat all that relates to this subject together, whether found in the 
introductory and concluding chapters or incidentally in other parts 
of the book. 
In the two chapters on the Anatomy of Vascular Plants added 
by Professor E. C. Jeffrey to complete the work, the author comes 
to a very definite conclusion which is best given in his own words. 
“ In the present state of our knowledge we are apparently justified 
in considering the Monocotyledons to be a modern, strictly mono* 
phyletic, and specialized group, derived from the Dicotyledons or 
their parent stock, possibly by adaptation in the first instance to an 
amphibious mode of life.” 
This opinion involves four separate conclusions: (i.) that Mono¬ 
cotyledons and Dicotyledons are derived from a single ancestral 
stock: (ii.) that this stock is geologically modern : (iii.) that the 
distinctive characters of Monocotyledons are specialized, not pri¬ 
mitive, or in other words that the common ancestor was either a 
Dicotyledon or a more primitive form which closely resembled one: 
(iv.) that the early Monocotyledons may have been evolved by 
adaptation to an aquatic habit. 
No such definite expression of opinion on this subject is found 
in the body of the work. The common origin of Monocotyledons 
and Dicotyledons is treated as an open question by the joint authors, 
and the evidence on both sides is given with admirable fairness. 
In the opinion of the present writer the balance of the evidence 
cited is very much in favour of such an origin, but the summing up 
on p. 283, and again on p. 287, is decidedly against it. The authors, 
however, agree so far with Professor Jeffrey as to allow that 
if such common origin be assumed, the derivation of Monocoty¬ 
ledons from Dicotyledons is more probable than the reverse (p. 286 
and again, p. 288). They express no opinion on the method of 
derivation. 
The section which deals with the reproductive organs and the 
gametophyte (Chaps. II.—VIII.) is in some respects the most 
remarkable in the book. It includes the whole story of “ double 
fertilization,” a subject in which the literature—though dating from 
1898 only—is so scattered that a resume of results together with a 
full bibliography was greatly needed. But apart from this, most 
botanists will be surprised at the amount of work dealing with the 
