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continue to develop along with the production of perithecia,
though in older spots the production of conidia diminishes until
finally a diseased area shows little but ripe perithecia, very few
conidia and very little of the mycelium remaining.
The growth of the mildew on greenhouse plants started in all
the cases observed on the upper surface of the leaves, the mycelia
appearing later on under the surface. None of the younger
spots on the under surface of the leaves were independent of
the mildew on the upper surface; it was always possible in the
spots examined to trace the mycelium connecting the areas of
mildew on both upper and lower leaf surfaces. Between Novem-
ber and May the mildew grew most abundantly on the upper
surfaces of the leaves and in many cases during December,
January and February there was no growth of mildew on the
under surfaces of the leaves. In May and June there was
abundant growth on both sides of the leaves, but after this
period the mildew grew most abundantly on the under leaf
surfaces producing no ascocarps on the upper parts.
For classes in mycology Sphaerotheca should prove to be a
very desirable type, since one may plan to have it in vigorous
growing condition for study at any specified time of the year.
From the time of sowing the seed of the host plant to the time
when ripe perithecia may be produced varies from five to eight
weeks according to conditions.
COLUMBIA UNIVERSITY, New YORK.
BOOK REVIEW
SCHAFFNER S FIELD MANUAL oF TREES*
Another book to add to the many reflecting the present interest
in nature study and helping increase such interest, this little
manual is both convenient and very usable. There are keys to
the trees in the summer condition based chiefly on leaves; in
the winter condition based on twigs and buds; to the fruits
and a general key based on both leaf and flower characters. The
last key seems unnecessary. The keys are simple and easily
followed through to the genera. Under these are keys to the
* John H. Schaffner, Field Manual of Trees, 3rd Edition, 154 pp., R. G. Adams
and Co. Columbus, Ohio, 1926. $1.50.
116
species where more than one is described. There is a brief
account of each species giving the general characters, habitat,
distribution, and the character and uses of the wood. All of
the native trees of the Northeastern United States and most of
these commonly cultivated for ornament or fruit are included.
The nomenclature is that of the second edition of Britton and
Brown. A single common name is given for each species,
though a few others are to be found in the index. The use of
synonyms and of several common names would have added
to the value of the book, especially where a tree is known by
different names in different regions. There is a glossary and a
complete index. The introduction attempts in six pages to
give an outline of all the activities of the growing tree from the
absorption of water to the development of seed. The book
easily fits in the coat pocket. It is well bound in semi-flexible
dark blue cloth and printed on good quality paper. It will be
helpful to all who wish to know the trees, especially as it can
be used at all seasons of the year.
Georce T. Hastincs.
PROCEEDINGS OF THE CLUB
MINUTES OF THE MEETING OF APRIL 28, 1926
This meeting was held at the Museum Building of the New
York Botanical Garden with Vice President Barnhart in the
Chair. The following were elected to membership in the Club:
Prof. Oakes Ames, North Easton, Mass.
Mr. E. J. Schreiner, New York Botanical Garden.
Mr. F. A. Varrelman, American University Campus, Wash-
ington, D. C.
Mrs. Britton read a part of a communication from the Com-
mittee on the Preservation of Natural Conditions of the Ecologi-
cal Society of America, in which it was suggested that the
societies affiliated with it contribute $1.00 to pay for the cor-
respondence involved in circularizing matters relating to the
preservation of natural features in the United States. By
vote of the Club this sum was appropriated.
The scientific part of the program consisted of a talk by Dr.
Arthur Hollick entitled “Recent discoveries of fossil plants