Recent Southern Appalachian Botanical Literature
Recent Southern Appalachian Botanical Literature
A recent paper in this journal announced the finding of Amphianthus pusillus Torr. in Rockdale County, Georgia, in shallow sandy pools on flat granite rocks. It had heretofore been known to science only from Stone Mountain, DeKalb Co. The Spring of 1937 was a favorable one for this species, with frequent rains as late as dried and broken leaves, still persisting in the parched soil, along with the rigid skeletons of Diamorpha. Later the same day the plant was found for the last time this Spring, in pools on a rock outcrop about 13 miles east of Eatonton, Putnam County. Only two plants were found, both brittle and desiccated, but recognizable by the trunk- like basal portion and the long-stalked floating leaves.
Much of the Central Upland of Georgia is underlaid by ancient granitic rocks which are frequently close enough to the surface so that considerable areas are exposed by erosion. The famous Stone Mountain, in DeKalb County, is the extreme example, but other such areas are frequent, although on a smaller scale. The surface of such exposed rocks is usually nearly level or somewhat rolling, although it may be very steep, as at Stone Mountain. The surface is also rather smooth, due to long weathering and exfoliation of the granite, and relatively little soil is formed on it. What soil is formed is coarse and sandy and usually only a few centimeters deep. It has long been recognized that these barren rocks sustained a peculiar flora, although to date Stone Mountain has attracted most of the attention in the area and other smaller outcrops have been unknown to or neglected by, botanists. Several species of plants are found only in the shallow soil surrounding these granite outcrops, and numerous others recall their maximum abundance there. In Georgia such things as Pilularia americana, Juncus georgianus, Arenaria brevifolia, Portulaca Smallii, Diarmorpha cymosa and Sedum pusillum are characteristically plants of this habitat, while others like Isoetes melanospora and Amphianthus pusillus are not found elsewhere. The literature contains a few references to the granite flora, one of the earlier being that by Dr. R. M. Harper, in 1900.
Some time ago my attention was called to the fact that some floral spikes of Spiranthes gracilis have the individual flowers arranged in spirals which ascend to the right, while others have the flowers in spirals which ascend to the left. In view of the extensive botanical literature on spiraling, a further study of this plant seemed indicated.