BOTANICAL SUEVEY— SUGAR GROVE REGION 267 



just enough to support it, but does not permit any but the slowest 

 growth. But whenever a break in the forest lets in the light, it is ready- 

 to spring up luxuriantly and cover the open places. 



It will be observed that this herbage is very similar to that of the 

 hemlock forest (see p. 269) which covers the hillside above the flat, and 

 it is clear that the two associations are closely akin. The one passes 

 into the other abruptly as the level land gives way to the hillside, the 

 place of Bciula lutea being taken by the hemlock, while the yew, the 

 ferns and the lycopod become more abundant. 



The one factor which more than any other appears to be responsible 

 for the development of this association is the absence of light. This is 

 pre-eminently an association of sciophytes. On both sides it is hemmed 

 in by lofty cliffs, which greatly reduce the light reaching the bottom. 

 The shade is so dense that of the many weeds which one finds starting 

 up in the spring all but a few stunted individuals have died off for 

 lack of light by mid-summer. A shade-enduring community is, how- 

 ever, of necessity slow growing, and when once the shade is removed, 

 this association has little chance of reproducing itself against the com- 

 petition of the aggressive, sun-loving plants which form the common 

 bottom-land association throughout the Central States. 



THE RIVER BANK ASSOCIATION 



"While the vegetation on the banks of the larger streams is a 

 heterogeneous mixture of all sorts of elements, especially annual weeds, 

 the banks of Queer Creek are covered in places with an association of 

 geophilous perennial herbs which is close to the natural condition. 

 This may be observed, perhaps to greatest advantage, on the banks 

 of the basin below The Falls at the head of ''The Gulf." 



It develops on banks which are too fre«iuently overflowed to permit 

 the growth of trees or bushes. Consequently it is well illuminated. 

 The soil is loose, almost pure sand, which is held in place by the under- 

 ground parts of the vegetation. 



The dominant plant is Panicttm latipoliI'M. with Carex prasina 

 and Senecio <iiir( its in considerable jibinidance. while Plilo.r inaculaia. 

 Rudheckia laciniata and Lobelia sijphiliiica ;ire usually presenl ;md, 

 by reason of their flowers, conspicuous. Wliei-c Ihe assoeialion is some- 

 what shaded, Lohelia cardi)wJis ap]>ears in nlmndrnc;', becor,iin<>' Ihe 

 fascies in August. 



