451 
waters. Production is deficient in vegetation-rich backwaters 
(Quiver Lake) and in excess in open reservoir lakes (Thomp- 
son’s Lake). 
1896. <A year of recurrent floods of moderate height and 
greatly diminished production in channel waters. The repeated 
summer invasions of the vegetation-rich backwaters by flood 
destroyed and removed much of the season’s growth, and we 
find this the year of greatest plankton production in these areas 
(Quiver, Dogfish, and Flag lakes). The more open waters, poor 
in vegetation (Thompson’s and Phelps lakes), have vernal 
pulses of considerable magnitude, but as summer and autumn 
production is not up to the average there is as a whole a defi- 
ciency in these areas. 
1897. A year of prolonged winter-spring flood, followed 
by continued and abnormally low water in the last 5 months 
of the year. The early flood apparently reduces production 
everywhere, while the prolonged low levels lead to abnormally 
high production in the channel and in vegetation-poor back- 
waters (Phelps and Thompson’s lakes). In Quiver Lake the 
relative dominance of vegetation and tributary waters of recent 
origin is so increased that production falls to alow level. Even 
tributary streams (Spoon River) so decline in run-off in the 
low-water period that an abundant plankton develops in their 
waters. 
1898. A year of normally located spring floods, followed 
by repeated minor flushes in summer and autumn. There 
is a meteoric but normally located vernal pulse, with a low 
level of production throughout the remainder of the year in 
the channel and in backwaters intimately connected with it 
(Quiver and Thompson’s lakes), and an abnormally high and 
well-sustained level of production in backwaters isolated from 
flood contact and free from vegetation (Phelps Lake). 
The different localities may be briefly characterized as fol- 
lows. 
Illinois River. Channel waters contain a plankton which 
in constituent organisms, character of the course of production, 
