Southeastern Washington and Adjacent Idaho. IOI 
The Chara-Potamogeton Associes 
In shallow ponds and small clear streams it is not an unusual 
sight to find the water rather completely filled with various sub- 
merged plants, of which sometimes Chara and sometimes Pota- 
mogeton pectinatus or P. californicus are dominant. Perhaps 
there occurs more often a mictium of the dominants of the two 
consocies respectively. 
In addition to Vaucheria, Stigeoclonium, and other algae, which 
are frequently very abundant in such situations, Najas flevilis, 
Zannichellia palustris, and Batrachium aquatile, also help make 
up the tangle of submerged plant life. 
The water crowfoot shows great plasticity in its habitat re- 
quirements, and as the ponds become shallower it is not unusual 
to find it dominating considerable areas of muddy banks. The 
aerial leaves with their well developed blades appear in striking 
contrast to the filiform submerged ones. 
The role of these submerged plants in the preparation of a 
suitable substratum for later stages in succession is frequently 
very marked. As a result of the dense aggregation of the indi- 
viduals of the constituent species of this community, bodies of 
water often exhibit a pronounced accumulation of debris consist- 
ing for the most part of the remains of former generations of 
aquatic plants and animals but mixed with fine soil particles 
brought in by the action of wind and water, the whole being 
effectively held in position by the expanding tangle of living 
plants. The accumulation of humus decreases the total amount 
of water in the substratum and the habitat gradually approaches 
a little nearer the mesophytic. As the bottom of the pond is 
slowly raised by the accumulating debris, the substratum be- 
comes relatively more compact. 
A continuation of these processes reacts unfavorably upon the 
submerged plants and they thus prepare the way for their own 
elimination. Not only is the reaction of initial stages of succes- 
sion unfavorable to the pioneer plant community but it also actually 
favors invaders. Plants with slender stems and floating leaves, 
such as Potamogeton and pond lilies, for a time take possession 
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