MARYLAND WEATHER SERVICE 263 



One of the most cosmopolitan of the ferns is Asplenium platy- 

 neuron, which occurs at frequent intervals in the woods, or more 

 noticeably along the roads, and similarly open localities, with no 

 evident regard to the soil upon which it may be growing. Thus if 

 the roadside is of good soil depth, as at the base of a moist hill, the 

 plants there will be of good development and be associated with 

 grasses and sedges. If the habitat is the dry exposure of massive 

 shale, as along the road over Sideling Hill, the associated plants will 

 probably be Poly podium, Asplenium trichomanes, Aster divaricatus, 

 Aquilegia canadensis, Quercus vehdina (in the adjacent woodland) 

 and Phlox subulata (on the edges of the exposed shale). By con- 

 trast, the selective habit of the two species, Asplenium pinnatifidum 

 recorded only at Weverton, and Asplenium ruta-muraria, at Wever- 

 ton, Cavetown, and Blairs Valley, northwest of Clear Spring, show 

 a low degree of adjustment of the life factors that control growth, 

 to the conditions in which the plants may find themselves. A notice- 

 able feature in this narrow range in adjustment is that the habitat 

 in which the plant is able to become established is one of extreme 

 unfavorableness, as judged by other plants which are so largely 

 absent in these latter cases from the immediate environment of the 

 plant mentioned. 



The upper portion of Sideling Hill is sandstone, and is there- 

 fore covered with the dry forest such as already has been listed 

 from several localities. Some of the areas upon the Hill have been 

 culled over so as to leave a poor representation of the original for- 

 est cover, but the species represented are not materially different 

 from those of this type on Tonoloway Ridge. A few herbaceous 

 plants not previously recorded were noted as: Senecio obovatus, 

 Eupatorium sessilifolium, Agvimonia pumila, Potentilla canadensis. 



There is a considerable valley to the west of Sideling Hill, but 

 it is narrower and more uneven than that about Hagerstown, which 

 has a floor in the form of a wide and comparatively level trough. 

 The former consists rather of a complex of small valleys associated 

 in one great one, the component units separated by hills and ridges, 

 so as to make the valley floor a rolling or undulating surface between 

 Sideling Hill and Martin's Mountain. 



