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110
page 125 of the Supplement) Hofmeister's clear statement made
in 1868, to the effect that mutation, rather than continuous
variation, supplies the material for selection in species making.
"New forms," said Hofmeister, "do not come into existence by
the summation in successive generations of small differences from
the customary form, all tending in the same direction; they
appear suddenly, and are widely different from the parent."
If America were as Teutonic in the matter of the publication
of scientific books, as it is in the organization of education,
and of scientific research, we would not have to rest content with
supplements, but would early enjoy an American translation of
the second German editions of works important enough to run
into a second edition. C. Stuart Gager.
Schaffner'* Field Manual of Trees*
As a field manual to slip in one's pocket, the present volume
will unquestionably fill a long felt want, as it condenses the
information contained in more complete works. The book is
scarcely more than one quarter inch thick, and only 6% X 4^^
inches long and wide. Brief descriptions are given for the genera
and species, but not for the familiek Keys are provided
throughout and the latter feature has been very thoroughly
covered. "Key to the genera of trees in the summer condition,"
"Key to the genera of trees in winter condition," "General key
to the families and genera," and "Key to the fruits" will give
some idea of the scope and usefulness of this side of the book."
In the appendix is a "General classification of the wood of trees
included in the manual" and a glossary of terms. The classifica-
tion of woods is based on their structure, porusness, and other
structural characters.
Of course the main body of the work is taken up with the
description of the individual species. All the usual features are
covered, tersely and concisely, and for practical field work, these
descriptions will be found quite adequate. There are notes on
* Schaffner, J. H. Field Manual of Trees, including southern Canada and the
northern United States to the southern boundary of Virginia, Kentucky, and
Missouri, westward to the limits of the prairie. Pp. 1-154. R- G. Adams Co.,
Columbus, Ohio. Price, limp cloth, $1.25; limp leather, Ii. 75. 1914.
Ill
the uses of the different species, and the geographical distribution
is given for each kind.
The nomenclature used is that of the second edition of Britton
and Brown's "Illustrated Flora," but the sequence of families is
that adopted in the work of Clements, Rosendahl and Butters in
their "Minnesota Trees and Shrubs," published in 1912. This
is the "Besseyan System" which differs from the Engler and
PrantI sequence in following the gymnosperms by the orders
Ranales, Geraniales, Malvales, Resales, Celastrales and so on.
One criticism that can be justly levelled at a purely popular
hand-book such as this are the names Cassiatae, Fabatae and the
like, which are categories readily understandable by the trained
botanist, but will be unfamiliar to the greater part of the readers
to whom the book is addressed.
As a workable pocket manual of trees, the book is sure to
have a wide range of usefulness. , , _
JN. 1 .
Warner, C. H., Formaldehyde as an Oxidation Product of
Chlorophyll Extracts, Proc. Roy. Soc. B. 87: 378-385, 1914,
reports a series of interesting experiments demonstrating the
production of an aldehyde when light acts on a film of chlorophyll
(prepared by allowing an alcoholic or ethereal chlorophyll
extract to evaporate on glass plates). The production of alde-
hyde goes on parallel with a bleaching of the chlorophyll, is
dependent on the presence of oxygen, but independent of the
presence of carbon dioxide. Along with the aldehyde a volatile
substance, capable of liberating iodin from a potassium iodide
solution, is produced.
In the same number of the Proceedings, Wager, H., The Action
of Light on Chlorophyll, Proc. Roy. Soc. B. 87: 386-407, describes
a more varied series of experiments covering essentially the same
ground. Warner is inclined to consider hydrogen peroxide the
active oxidizing agent, produced in the presence of oxygen and
light, which attacks the chlorophyll ; Wager argues that probably
some other peroxide is concerned.
This work again shows that the original experiments with
chlorophyll films as performed by Usher and Priestley did not