422 BOTANICAL GAZETTE [MAY 
alkaline; only for a few days in August was acid present, and then 
the amount was almost negligible. 
Subterranean organs and their interrelationships 
A study of the subterranean organs of the reed swamp plants 
showed that in many cases the depth is roughly proportionate to 
the depth of the water table. Yapp (19) arrived at a similar con- 
clusion concerning the plants at Wicken Fen. And since the depth 
of the water table may influence the depth of the subterranean 
Surface 
EES del. 
Fic. 4.—a, Sparganium eurycarpum; b, Sagittaria latifolia; c, Polygonum Muhlen- 
bergii; July. 
organs, the latter in turn may enter as a potent factor into the 
success or failure of various species. Thus, for example, the 
rhizomes of Polygonum Muhlenbergii, where this species occurs in 
the Sio-polygonetum, are usually at or near the surface of the 
stream bed. As Kine (8, p. 240) and others have pointed out, 
saturated soil like that of the stream bed does not admit oxygen 
freely. And so, in the Sio-polygonetum, the rhizomes of Polygonum 
and their roots appear advantageously placed. But in the Scirpo- 
typhetum (fig. 4), where the surface soil is occupied by an extremely 
dense mat composed of the rhizomes of Typha, Sparganium, and 
