199] FLORA OF COLUMBIA AND VICINITY 57 



mosses, ferns and lichens constitute often the greater portion of 

 the vegetation. 



1. Rupestres fontinales. The fontinal cliff vegetation 

 occupies moist rocky banks, damp ledges, and dripping rocks. 

 It is the most delicate of all plant formations in the region. 

 Three strands of fontinal vegetation are discernible, a. The 

 strand of gregarious liverworts, mosses, and walking ferns, cov- 

 ering slabs of rock in the streams, and the dripping ledges of 

 the cliffs, b. The strand of fontinal ferns and cresses on wet 

 rocky banks. Where it adjoins the preceding it lies above it. c. 

 The strand of moist cliff plants, such as Senecio aureus, Eupa- 

 torium ageratoides , and the lyme grasses, Elymiis spp., which 

 occupies the upper portions of the fontinal subzone. Certain 

 riparian trees and shrubs occur, but only Physocarpus is char- 

 acteristic. 



a. Fontinales scolopendrioides. The walking fern as- 

 sociation of liverworts, mosses, and ferns, occupies the lowest 

 portion of the fontinal subzone. The walking fern {Scolopen- 

 drium rhizophyUum) is remarkable for its propagation by means 

 of little plants borne at the apices of its fronds, thus enabling 

 the plant to climb up the sheer faces of rocks. The principal 

 liverworts are Marchantia polymorpha, Conocephalus conicus, 

 Grimaldia riipestris, and Dumortiera hirsuta. A few phan- 

 erogams, such as Pilea pumila, Erigeron Philadclphicus, and 

 Solidago flexicaulis, are frequent also. 



b. Fontinales cystopteridoides. The bulbet-fern as- 

 sociation of ferns and cresses occupies the central portion of 

 the fontinal subzone. It consists of a layer of ferns, mingled 

 with rock-cresses and other moist-rock plants. Cystopteris bul- 

 bifera is especially common, its narrow fronds being often pro- 

 longed to a length of a metre or more. C. fragilis, Woodsia 



