160 BOTANICAL GAZETTE [auGuUST 
- rots of the Solanaceae and on the tobacco wilts with their confusion of diseases 
described from different parts of the world and attributed to various organisms. 
It is the great merit of the author to have contributed so largely to the field 
of plant bacteriology. It is an almost equal merit to have clearly pointed out 
the lines for future progress—H. HASSELBRING. 
MINOR NOTICES 
A popular guide to mosses.—Mrs. DUNHAM? has undertaken to present 
the mosses of the northeastern states in a non-technical way, so that the 
amateur may recognize at least their genera without using even a hand lens. 
The result is a very attractive little book, whose simple language and marginal 
illustrations should accomplish the purpose announced. If it succeeds, it will 
open up to the general student a group of plants present in every flora, and 
usually regarded as too difficult for even a speaking acquaintance.—J. M. C. 
Plant diseases.—A second edition of MAssEE’s’ very useful manual has 
just appeared, 5 years after the publication of the first edition. It differs 
from the former edition only in containing a supplement of 16 pages, giving 
statements concerning 20 diseases which are not included in the body of the 
text, or concerning which additional information is given.—J. M. C. 
NOTES FOR, STUDENTS 
Evolution of species in Ceylon.—WILLIs° has followed his recent paper 
on the endemic flora of Ceylon’ by developing still further his argument against 
natural selection as an explanation of the geographical distribution of species. 
is argument is based mainly upon statistics derived from TrimEn’s Flora 
of Ceylon, in which the species are divided into 6 classes, ranging from ‘“‘ very 
common”’ to “very rare.’ He observes that in Ceylon the endemic species 
are the rarest, according to the foregoing classification, while species which 
are widespread outside of Ceylon are commonest there also. This not only 
appears from a consideration of the flora as a whole, but in every family the 
endemic species are the rarest. It also appears that within every family the 
groups of species into the rarity classes are remarkably alike. Wu£tis regards 
these phenomena as the result of some natural cause working with practically 
even pressure throughout the whole plant kingdom, a cause entirely unlike 
natural selection, which is essentially differentiating in its results. This 
# Dunua, ExizapetH Marte, How to know the mosses; a popular guide to the 
mosses . the no gta United States. 8vo. pp. xxv+287. Boston: Houghton 
Mifflin Co. 1916. $r. 
shee. Gicees. Dincates . orgieas plants and trees. 8vo. pp. xii+-602. 
Sigs. 173. = York: Macmillan 
§ Wis, J. C., The ovation - us in Ceylon, with reference to the dying 
out of aie Aum: Botany 30:1-23. 1916. 
7 Bor. Gaz. 61:82. 1916. 
