1921] Peattie, — An Interesting Habitat 69 



AN INTERESTING HABITAT. 

 Donald C. Peattie. 



It is not uncommon to see in hilly or more frequently in moun- 

 tainous countries a special type of plant habitat which though of 

 considerable botanical interest and sufficiently common and beautiful 

 to attract general notice, has nevertheless been very little treated in 

 scientific works. 



This peculiar condition consists in a face or precipice of rock with 

 frequently a sloping shelf below, and a continual seepage of water 

 across the upper rock down on to the lower one. This is an essen- 

 tially hydrophytic habitat, yet it is an aerial one too. Rock-loving 

 and crevice-loving plants are at home here, and their foliage and often 

 the long strands of their roots hang down the walls of the cliff. We 

 are apt however to think of plants upon cliffs as xerophytes, and in- 

 deed they usually are. Lichens, certain saxifragacious plants, and 

 such ferns as Cheilanthes and Polypodium come to mind. However, 

 in the situations such as we have been describing, it is rather the 

 hydrophytic or semi-hydrophytic plants which we find. For this 

 particular combination of physical conditions of plant growth, one 

 might propose the name Grotto, owing to the resemblance to the 

 popularly so-called physiographic feature. 



Grottoes are local though not rare, and may be found wherever 

 there has been erosion into glens, and where there are abundant 

 springs. The writer is familiar with them in the southern Appalach- 

 ian system, and they are said to be common in the limestone moun- 

 tains of Vermont and in the Laurentian Highlands. In the Middle 

 West they are frequent in those pretty canyons cut into the lime- 

 stones and sandstones of Indiana, Kentucky, Ohio and other states. 



Grottoes may be seen in all stages of what we may term their 

 conquest by plants. First of all we have merely the naked rock, 

 or as they term it in the South, the "slick rock." By "slick" is 

 meant a rock which is smooth, steep, and dripping with water. In 

 the next stage the water has brought algae with it and these plants 

 may be seen as pale green stripes upon the face of the cliff. Later 

 mosses and liverworts lodge in the crevices, and soon they will take 

 possession of the shelving ledge below. The Bryophytes will at 

 length so mat the surface with their roots and break the force of the 



