392 Wisconsin Academy of Sciences, Arts, and Letters. 
Zone 2 is of approximately the same size in both lakes, but has 
a considerably higher yield in Mendota. Zone 3, on the other hand, 
is slightly larger in Green Lake, and considerably more productive. 
Putting the facts in a different way, in Green Lake, about 9 per 
cent of the vegetation is in water less than 1 meter deep, about 40 
per cent between 1 and 3 meters, and more than 50 per cent be¬ 
tween 3 and 8 meters (table 12) ; whereas in Mendota 30 per cent 
is found in the shallowest water, 45 per cent between 1 and 3 
meters, and only 25 per cent in water deeper than 3 meters. 
About one-half of the entire vegetation (dry weight) is com¬ 
posed of Chara (table 11). In shallow water (table 3), this is 
everywhere fairly abundant except at the east end of the lake 
where the bottom is muddy (in the other swampy places there 
seems to be more sand mixed with the mud). It is most frequently 
associated with Potamogeton heterophyllus and small amounts of 
Naias; often it is mixed also with P. pectinatus, Heteranthera, and 
Vallisneria. In Zones 2 and 3 (tables 4 and 5), the distribution of 
Chara is about the' same as in Zone 1, but it is usually mixed with 
most of the other species. Where it occurs unmixed, it is present 
in very great abundance. One sample of Chara, gathered from 
0.25 square meter, weighed 2,700 grams (wet). 
The various species of Potamogeton form about 20 per cent of 
the total flora. Potamogeton occurs abundantly in shallow water 
only in a few stations of different characteristics. In Zone 2, how¬ 
ever, it thrives everywhere except for a few stations along the 
north and west shores. Restriction of Potamogeton in these places 
may be due to greater wave action. The shores here are of the type 
shown in fig. 1. In the northwest corner of the lake, Potamogeton 
is for some reason almost entirely replaced by Drepanocladus, here 
present in great quantity. In the deepest zone, species of Potamo¬ 
geton are not abundant, except P. zosterifolius. 
Ceratophyllum and Myriophyllum rank next in importance, 
each forming about 10 per cent of the vegetation. The former is 
found in abundance only in Zone 3, and is there universal. The 
distribution of Myriophyllum is similar, but its range is slightly 
shallower; it is found more commonly than Ceratophyllum in 
Zone 2 and does not extend down quite so far as the latter plant 
(table 12). A visit to the bottom 7 or 8 meters below the surface 
reveals a forest of almost pure Ceratophyllum; whereas at 5 or 6 
meters, while the general appearance of things is the same, the 
vegetation is about half Myriophyllum. 
