Rickett—The Larger Aquatic Plants of Lake Mendota. 509 
Total Weights . The total areas of the different zones were ob¬ 
tained from Mnttkowski’s work (4, p. 470). For the third zone, 
it was assumed that the outer limit of the vegetation corresponds 
on the average to the 5-meter contour line; that is, that the area 
of plants without this line equals the plantless area within it. 
The total weights of the different species in each zone and in the 
plant zone as a whole were determined from the weight per square 
meter and the total area. These figures are listed in table 7. The 
final figure arrived at for the total weight of plants in the lake is 
close to that already arrived at in table 3, the difference being of 
course due to the fact that samples have different amounts of 
weights in the various calculations according to zones which they 
represent—the latter being unequal in area. 
Comparative Tables. Table 8, derived from the preceding table, 
shows the amount of each species, in each zone, and in all zones 
together, in terms of the total weights. The relative amount of 
each species found in each zone is given in table 9, also calculated 
from table 7. 
The Shaelow Bays 
The data obtained so far have reference only to the large bulk 
of the lake flora which is found in the uninterrupted zone that 
follows the shore. It remains still to consider the case of Clado- 
phora and that of the vegetation of the shallow bays. 
Bays of different sizes are found in stations 4, 27, 29, and 30. 
In all but that in station 29, the bays are separated from the main 
body of the lake by bars. In the first two cases the bars are com¬ 
posed mainly of sand and gravel, in the last of rocks. In all cases 
the ordinary plant zone extends continuously outside the bars. 
Within the bars, the growth is of an entirely different character. 
In University Bay (station 4), almost all of the species of plants 
found in the lake are present in a dense, tangled growth. Col¬ 
lections were made in the central portion of the bay from the 
shore to the bar, at intervals of about 50 meters. In this way, 
representative samples of each type of vegetation present were 
obtained in a proportion approximating their distribution. From 
these samples was calculated the average weight per square meter 
of each species for the bay. The area of the bay was measured 
on the map by means of a planimeter. The total weight of each 
species could then be determined from these figures. 
