330 
BOTANY: E. W. BERRY 
of the latter substance the logarithm of b was plotted with the density 
in order to bring out more clearly the relation of the various 5 values to 
the density although an inspection of the tabulated values show that 5 
is constant. It might be added that helium, while the data are less 
extensive, gives identically the same result as does argon. 
In tables 1 and 2 will be found the comparisons of the pressures calcu- 
lated for the volumes and temperatures as given by Amagat for nitrogen 
and CrommeHn for argon. The nitrogen pressures calculated show 
about as good an agreement throughout with the observed pressures as 
could be expected. 
THE CLASSIFICATION OF VASCULAR PLANTS 
By Edward W. Berry 
GEOLOGICAL LABORATORY. JOHNS HOPKINS UNIVERSITY 
Communicated by W. Trelease, February 14, 1917 
A scientific knowledge of plants or other natural objects consists to 
a very considerable extent in a knowledge of their mutual (phylogenetic) 
relations, hence the necessity of a Taxonomy that will consistently 
express filiation, which is only another way of stating that it should 
be phylogenetic. Science does not consist merely of names, but it 
cannot very well progress without a terminology, and not until 
this terminology becomes an expression of evolution can it become 
consistent and itself scientific. 
Botanists have rather effectually grappled with this problem in the 
case of the lower plants, but the classification of the so-called vascular 
plants remains largely as an inheritance from the study of the end 
products of their evolution, namely a study of the existing vascular 
plants, with but slight consideration of the recent progress of paleo- 
botanical investigation. 
The not so very long obsolete practice of considering the Angiosperms 
and the Gymnosperms as subclasses of the class Exogens was a no more 
pernicious mask of their true relations than the extant usage which 
considers vascular plants as separable into two great phyla — the Pteri- 
dophyta or Sporophyta and the Spermophyta. With the subdivisions 
of these two groups the present situation is equally inexpressive of our 
present state of knowledge. To the paleobotanist the Angiosperms and 
the Gymnosperms are obviously not groups of the same order, the 
latter including several groups of comparable rank with the Angio- 
sperms as a whole, and extending over a period of time expressed by 
the ratio of 21 for gymnosperms to 6 for angiosperms. 
