440 Wisconsin Academy of Sciences, Arts , and Letters. 
of root stocks and roots, and in the size of the clumps of culms. 
Carex aquatilis is large and coarse, has few culms in a clump 
and produces most definitely the two kinds of roots (See Plate 
XXI. The rootstocks and soil roots often grow to he a foot 
long and both are provided with aeriating tissue. The soil 
roots have no branches. The method of branching is the same 
as noted for Car ex stricta. Car ex riparia is similar but is still 
coarser in growth and produces roots from the rootstock (See 
Plate XXII. The rootstock of Carex Sartwellii does not branch 
much laterally (See Plate XXII). 
Compared with these sedges Calamagrostis canadensis has a 
fine and much branched underground rootstock system which 
fives nearer the surface. The roots are all finely fibrous and 
the branching that results in aerial shoots is loose. 
The general adaptations of these plants have been repeatedly 
pointed out. The conditions require a superficial or at least a 
shallow root development. This limits the aerial growth and 
forces exposure to sun and winds. The herbaceous habit is 
adapted to the seasonal extremes of aerial conditions. The 
rhizomes provide for spread and for perpetuation. The abun¬ 
dance of root development with air chambers in roots, rhi¬ 
zomes and scales is adapted to the water and soil conditions. 
Yapp (24) (1909) has pointed out the unsatisfactory state 
of our knowledge of the adaptations of xerophytic swamp plants. 
His studies of the evaporation at different levels show a marked 
corellation of the stratification of the plants with the varying 
amounts of evaporation. The xerophytic leaf structures de¬ 
velop in the upper levels while the mesophytic are below in the 
zone of decreased evaporation. He considers that the aerial 
structures are adaptations to the extremes of evaporation that 
exist. 
The view that swamp xerophytes are results of the physio¬ 
logical dryness of the swamp habitat is somewhat in question as 
Clements (21) (19051 emphasizes. He considers that the 
xerophytic structures of such plants are not due to presence of 
humic acids in the soil but that these features “are due to the 
persistance of stable structures which were developed when 
these species were growing in xerophytic conditions.” 
