278 
Review. 
minutely subdivided, there seems no very strong reason for 
retaining such a genus as Planoxylon, which has no characters by 
which it may be distinguished from Protocedroxylon, a name 
accepted by Professor Seward without comment, though Dr. 
Stopes considers that it is objectionable on the ground of 
unfounded implications of affinity. 
A consideration of the evidence so carefully brought together 
and arranged by Professor Seward shows that we are not yet in a 
position to give conclusive answers to the many interesting 
problems connected with the phylogeny of the Coniferales. While 
stating that the group is probably monophyletic, Professor Seward 
refrains from giving any decisive opinion as to the stock from 
which it sprang. He thinks that the weight of evidence is in 
favour of the Araucarineas being older than the Abietineae, but 
that at present we can say little more definite than that the latter 
had a later maximum development than the former. The evidence 
from foliage shoots and cones is somewhat uncertain, but the fossil 
wood points to the Araucarineae as being older, though Cordaitean 
and Arancarian woods have not yet been satisfactorily separated. 
Professor Seward is very cautious about most supposed pre-Jurassic 
Araucarians, though he thinks that many forms ( e.g . of Walchia , 
Voltzia and Ullmannia) show undoubted Araucarian affinities. 
He concludes that the Araucaria type is older than that of Agathis 
(Araucarites Delafondi from the Permian is one of the earliest 
definite examples of an araucarian cone-scale), and points out that 
this once cosmopolitan family continued to flourish in the northern 
hemisphere till well into the Tertiary period. 
It is unfortunate that the Podocarpineae, which may be allied 
to the Araucarians, are very unsatisfactorily represented in the 
geological sequence, and records of undoubted Taxineae are also 
very rare. The Cupressineae and Abietineae were abundant in 
later Mesozoic times, though correlation with living genera is 
difficult, and there are many fossil forms which cannot even be 
placed with certainty in any particular family. It is to be hoped, 
as Professor Seward suggests, that the cuticular study of these 
impressions will be of some help in classification, for little has 
been done in this direction so far. 
In conclusion, one may say that this volume marks a definite 
stage in our knowledge of the past history of the conifers, and it 
indicates clearly the gaps which must be filled in by future 
investigation. It is a matter for regret that the fossil Angiosperms 
are not yet ripe for similar treatment, and that this important 
work is now concluded, but all botanists will look forward eagerly 
to Professor Seward’s promised general survey of past floras, 
which could not be included in a descriptive text book. 
W. N. E. 
