Bickett—The Larger Aquatic Plants of Green Lake. 383 
facts. On the other hand, vegetation is very abundant in the 
deeper waters, and descends to a greater depth than in Mendota. 
Besides the main plant belt, consisting entirely of submerged 
plants, there are near the marshy shores regions well populated 
with emersed and floating forms, which merge gradually into the 
flora of the swamps themselves. 
Methods 
The apparatus was the same as that used on Mendota. The vari¬ 
ous stations for collecting were reached by means of a rowboat 
equipped with a detachable motor. An iron frame, half a meter, 
on a side, was let down to the bottom, and all plants falling within 
the area thus limited were gathered. Depths up to 3 meters 
were reached by ordinary diving. Collections in deeper water (up 
to 10 meters) were made by means of a diving hood, supplied with 
air by a hand pump in the boat. This device permitted almost as 
intimate an acquaintance with submerged plants in their habitat 
as can be enjoyed with land plants in theirs. It was found pos¬ 
sible to stay down from 15 to 20 minutes, and to explore a con¬ 
siderable portion of the lake floor. The water of Green Lake being 
comparatively clear and admitting a fairly bright light to these 
depths, this method of survey furnished an accurate idea of the 
kinds of plants present, the uniformity of their distribution, and 
the downward extent of the plant belt. It is interesting to note 
that the decrease in illumination is very rapid in water deeper than 
8 or 9 meters. At 7 meters there is what seems to be fairly bright 
sunlight; at 10 meters one is almost in darkness. 
A section of shore of uniform general characteristics usually has 
opposite to it a section of the plant belt of fairly uniform nature 
throughout. Stations were therefore chosen on the basis of the 
character of the beach, and of the shallow water flora. The num¬ 
ber of stations that can be made in this way of course depends 
largely upon convenience, since in many places the flora varies 
greatly within a small area (for instance, in the densely populated 
Stations 1 and 2). The plant belt was divided into 38 stations, 
with 3 additional stations representing the marshy bays. This 
was about the smallest number which would fairly represent every 
type of vegetation and at the same time include the whole circum¬ 
ference of the lake; it would not have been possible to collect thor¬ 
oughly from a larger number. The stations used are shown by 
number on the map (fig. 4). 
