444 BOTANICAL GAZETTE [JUNE 
When such anchored forms, especially the strong ones like 
Nuphar, gain a good footing, the floating mat vegetation fol- 
lows apace. Several species of Utricularia aid greatly in this 
process, by means of their floating and branching tufts. Sphag- 
num and other mosses, Carices, Xyris, and Drosera appear. 
In still further building the mat, and in giving it firmness, 
| Decodon verticillatus plays a leading part. Several adaptations 
give it its preeminence, namely, the firmness of its woody roots 
and stem bases; its ability, nevertheless, to grow almost float- 
ing, only slight support being necessary; and its power of 
propagating from the tips of its shoots wherever they touch the 
water. The woody parts mentioned are clothed with thick 
layers of aerenchyma. Probably this tissue is not only a means 
of respiration, but also of importance in floating the plant. 
_ Decodon occurs almost universally in the yielding ponds. 
We have seen that in Long pond, an open lake, the vegeta- 
tion is purely hydrophilous. About the time of the formation 
Of the floating mat, the general conditions rapidly become xero- 
a ollowing Decodon, and finding footing on its stools, 
i ebaceabie that these ehruies out | 
alliances, have a certain common 
imple, lanceolate, are entire and 
eiore the shrubs, and in due time 
beg appear. As these trees, often wholly 
row, ‘the shrubs are overtopped and yield, and 
the series Kee final cycle as a Chamaecyparis swamp. : 
: v the iene diate seit of Woods ee 
