Rickett—The Larger Aquatic Plants of Lake Mendota. 505 
those in deeper water, and, partly for this reason, collections from 
shallow regions were completed before any were made from 
deeper points. 
In the cases of the several shallow bays, usually separated from 
the main body of the lake by bars (see map), the problem is differ¬ 
ent. The character of the flora is entirely different, the growth 
is very dense, and collection is difficult. The best that could be 
done in the limited time available was to estimate by eye the pro¬ 
portions of various plants or types of growth, and to take repre¬ 
sentative samples from each. 
It was necessary to handle Cladophora separately. The period 
of greatest growth of this plant extends roughly over the first 
weeks of June, before the other plants of the lake have reached 
their full size. This time was therefore spent in a detailed sur¬ 
vey of the entire shore with reference to the distribution of Clado¬ 
phora, and in the obtaining of samples. Some Cladophora occurs 
on rocky bottoms in deep water, but the amount is too small to 
be taken into account. 
Data Obtained. With the exception of the two special cases 
last described, the following observations were made in the field 
in the case of each sample: the number of the station; the num¬ 
ber of the sample; the date; the depth of water; the distance 
from shore; the character of the bottom; and the area from which 
the sample was obtained. A specimen set of data for one station, 
involving several samples, is shown in table 2. 
Weighing the Samples 
Separation of Species. The samples were brought back to the 
laboratory and separated into the various species of which they 
were composed. The ease with which this could be done varies 
greatly in different cases. Some plants, such as Chara and Cera- 
tophyllum, grow in some places very intimately mingled with each 
other and with other species, and absolute separation is next to 
impossible. 
The large number of the sub-samples separated in this way—730 
—is the best argument for the approximate accuracy of the final 
results. 
Wet Weight. For obtaining the wet weight, an ordinary 
household scale, graduated so as to read in fractions of a kilo- 
