539 
etc.,and their equivalents, containing many genera identical with 
those now living, must have had a more simple ancestry, and in 
the lower Potomac and Wealden this ancestry seems to be repre- 
sented, and on plates cvi. and cvii., figures are given of some .of 
these plants from both foreign and home ‘localities, in order. that 
they may be compared. Such an eminent authority as Saporta 
was in doubt as to their precise affinities, and classed them-all un- 
der a special group, which he dalled Proangiosperms. When the 
entire flora of the lower Potomac shall have been described; we 
may hope to have many more representatives of these archaic 
types which will be of absorbing interest to the student of plant 
development. Ait. 
Grasses of North America. WJ. Beal, M.A., M.S., Ph.D., Pro- 
fessor of Botany and Forestry in Michigan Agricultural Col- 
lege. 2 volumes. Henry Holt &Co. | 
The first volume of this work appeared in 1887, and was de- 
voted to a consideration of the physiological and economic part 
of the subject. The second volume, which has just been pub- 
lished, treats of the grasses from the standpoint of the systematist. 
A classification of all the forms growing wild and introduced in 
North America and Mexico is attempted, the inclusion of those 
from the latter country much increasing the difficulty of the under- 
taking. The value of the work is greatly marred by the treat- 
ment of the plants in too large and comprehensive groups. This 
applies both to genera and species. To illustrate this in relation 
to genera, Andropogon may be selected as an example. In this 
such good and well-marked genera as Sorghum, HHeteropogon and 
Chrysopogon, natural groups that are altogether too distinct to be 
considered as mere parts of one group, are included. In Panicum 
this same plan of extreme aggregation has been followed, both 
generically and specifically. In P. dichotomum 1. the objection- 
able feature of this method is particularly noticeable. Six or 
eight good and valid species are here treated as a polymorphous 
one. While there may be considerale trouble as yet with the 
forms which have been called P. pubescens of Lamarck, certainly 
Such well-marked grasses as P. ciliatum EAL, P. ensiflorum Baldwin, 
and what is called 2. dardulatum Mx. are clear and distinct enough 
_ from casual observation to be kept apart as specifically distinct. 
a 
