376 
mulated before the deciduous forest appears. 
Swamp series and clay soil series show 
similar stages before the climax deciduous 
forest society is made possible. In every 
instance there must be a coniferous or 
poplar-birch forest before the maple-beech 
deciduous forest, for in that way only can 
shade conditions be obtained for the pro- 
tection of maple and beech seedlings. 
Application of the Quantitative Method to the 
Dynamical Study of Plant Societies: HENRY 
C. CowLEs. 
The vegetation in the vicinity of Chicago 
is being systematically mapped from an 
ecological standpoint, topographic maps 
being used as a basis for work. By means 
of accurate mapping and recording of field 
observations at selected points, it is hoped 
that sets of data may be obtained showing 
the rapidity of encroachment of one plant 
society upon another. By means of photo- 
graphs taken at one-year intervals consid- 
erable, change has been found in the dune 
region, and this suggests the desirability of 
a similar;study for other plant societies. 
An Anatomical Classification of Vascular Plants : 
EK. C. JEFFREY. 
The use of the skeleton in the phyloge- 
netic study of plants has been almost en- 
tirely neglected. In recent years paleo- 
botanists have done something to remedy 
this defect, but they have been without the 
importantiaid furnished by the study of 
development. The present article, illus- 
trated by a large number of photographs of 
the vascular skeleton of living and fossil 
plants, andjespecially the developing skele- 
ton of extant groups of plants, is intended 
to show that there are a number of abso- 
lutely constant and characteristic anatom- 
ical criteria. 
Stomata of some Liliacee: EK. P. CopELann. 
The stomata of Liliacece are very diverse 
in structure, but most of them are well built 
to openand shut. Many of them ( Uvularia, 
SCIENCE. 
[N. S. Vou. XIII. No. 323. 
Smilacina, Polygonatum, Dracenam, Smilax, et 
al.) are so circular in surface view that an 
increase in turgescence would not open the 
pore if the walls at the ends of the guard 
cells were not much more rigid than those 
of their backs. This rigidity is secured by 
special local thickening, or by the mode of 
insertion of the walls of adjacent cells. 
The stomata of Medeola are also circular, 
but the backs are strengthened by folds in 
the wall. The pore opens by an increase 
in the depth of the guard cells, 7. ¢., at right 
angles to the surface of the leaf. It is a 
perfect development of what has been called 
the Mucinus type of stoma. 
Methods of Plankton Measurement: JAcoB 
ReEIGHARD and Henry B. Warp. 
The paper presented a brief review of 
methods introduced by Hensen, and used 
by a number of observers for computing 
the amount of plankton obtained by hauls 
of a vertical net, and of the calculations on 
theoretical and experimental bases given by 
Hensen, Reighard and others for determin- 
ing the coefficient of the net, 7. e., the frac- 
tion of the column of water which actually 
passes through it. The authors propose to 
determine the coefficient by actually meas- 
uring the amount of water passing the 
mouth of the net. This is to be accom- 
plished by means of a three-vane meter sus- 
pended in the axis of the net opening a short 
distance inside its upper rim. By means of 
an electric pen register the revolutions of 
meter are recorded on a tape, and parallel to 
them, both the starting and stopping signals, 
and the time record from the chronometer, 
from which it is possible to calculate the 
number of revolutions in the time of the 
haul, or the time or revolutions in any de- 
sired fraction of the haul. The difficulties 
and errors in the management of the ap- 
paratus were discussed, together with the 
means for detecting them. The rating of 
the meter by two different methods was 
