LAKE BLUFF, RAVINE, AND RIVER VALLEY 265 



the walls are found plastered with liverworts, Conocephalus 

 being the prevalent one Marchantia (Fig. 397) less common. 

 Mosses are abundant. The purple- 

 stemmed cliff brake (Pellaea atropurpurea) , 

 recognized readily by the location and 

 its slender purple stem, is noticeable. 

 Selaginella grows in beautiful masses 

 (Fig. 398); wild hydrangea is present as 

 an interesting shrub in the ravine bottom 

 (Fig. 399) ; touch-me-not, early saxifrage, 

 river horsetail, and other plants demand- 

 ing much shade and moisture, are preva- 

 lent in the bottoms of the ravines. Bank 

 swallows and occasionally rough-winged 

 swallows nest on shelves of the rocks. 

 The mourning dove, the wood peewee and ruby-throated hum- 

 mingbird build on the overhanging shrubs. Snails crawl about 



FIG. 396. Bladder fern, 

 Cystopteris bulbifera, upper 

 right, under side of frond; 

 upper center, one sorus. 



397 



FIGS. 397-398: Fig. 397. A liverwort, Marchantia polymorpha, bearing 

 archegonial branches. Upper right, portion of thallus with gemmae cups. After 

 Atkinson; Fig. 398. Selaginella rupestris. After Andrews. 



