410 Wisconsin Academy of Sciences, Arts, and Letters. 
Car ex vesicaria, and Car ex riparia, with Equisetum limosum, 
Equisetum palustris, Hypnum species, and Cladium maricus 
as secondary species, and as less frequent Menyanthes trifoliata 
and Heleocharis palustris. They also note that “on drier places 
this association is quickly replaced by a Molinietum” or a more 
purely grass association. 
Feilburg (8) (1890) has studied the influence of the depth 
of the ground water on the vegetation of marshy sand plains in 
Jutland. He claims that, the chemical and physical composi¬ 
tion of the soil being uniform', “when the ground water in sum¬ 
mer stands at a depth of three inches Juncus and meadow moor 
vegetation prevail; at six inches mosses and Cyperaceiae still oc¬ 
cur but grasses begin to appear; at nine inches these taller be¬ 
come dominant; at twelve inches normal grass growth occurs in 
ordinary summers; at from eighteen to twenty-four inches 
cereals thrive in cold moist summers, at from thirty to forty 
inches the soil is unsuited for cereals and xecophytes predomi¬ 
nate.” According to Feilburg the depth of the water table is 
here the sole factor determining the natural vegetation that ap¬ 
pears and the crops that can be grown. 
As to the physical characteristics, soil composition and dis¬ 
tribution, Whitson and Jones (23) (1907) distinguish two 
types of marsh lands in Wisconsin. The one most abundant in 
Horthern Wisconsin is in the sandstone and granite regions, as 
a rule, and is the typical bog formation with sphagnum,^ tama¬ 
rack, and spruce. The soil is strongly acid and is deficient in 
available potash and phosphoric acid. The second type is the 
marsh meadow or meadow moor best developed on the lime stone 
area of the eastern and south eastern part of the state. Here 
the peat shows little or no acidity, is deficient in potash but less 
so in phosphoric acid. To this latter type belong the wild hay 
marshes of this portion of the state 
The region about the city of Madison is especially favorable 
for the study of marsh formations and I have undertaken to 
analyze the flora of a typical formation of this class by statisti¬ 
cal methods with the aim of obtaining the numerical relations, 
and the relative importance of the various species as they are 
grouped in such an association. 
