340 



SCIENCE. 



[N. S. Vol. XVIII. Xo. 4r)4. 



of an open type-witli the presence of a large 

 number of shade-loving plants, such as San- 

 guinaria canadensis L., etc., which are not 

 found as constituents of the barren flora. 



Ten representative serpentine barrens were 

 studied by the writer, viz:* 



A. Glenriddle, Delaware County, Pa., on 

 the road leading to the borough town of Lima. 



B. Serpentine in the valley west of Black 

 Horse Hotel. 



G. Serpentine east of Black Horse Hotel. 



D. Serpentine at Williamson School. 



E. Serpentine lying between Newtown 

 Square and Darby Creek. 



F. Serpentine opposite Castle Eoek on east 

 side of Crum Creek along Preston Run. 



G. Serpentine near Westtown, Pa. 



H. Pink Hill near Lima, Delaware County, 

 Pa. 



I. Brinton's Quarry near Westtown, Pa. 



Ecologically the flora of the serpentine bar- 

 rens belongs to the mixed deciduous forest and 

 barren treeless formations. Several plant as- 

 sociations are recognizable, so that an ecologic 

 classification of the plants is as follows : 



Mixed Deciduous Forest Formation. 

 Juniperiis-Acer-Nyssa-Quercus Associa- 



Hon. 

 Sassafras Association. 

 Aspidium-Asplenium Association. 

 Dichsonia Association. 

 Barren Treeless Formation. 

 Gerastium Association. 

 Phlox Association. 

 Deschampsia Association. 

 Garex-Eleocharis Association. 

 Spircea Association. 

 Bosa Association. 

 Rubus Association. 

 Kalmia Association. 

 Smilax Association. 

 These formations and associations will be 

 described as they exist on the several serpen- 

 tine areas mentioned. They are controlled 



* The map used in this botanic survey aecom- 

 panies Perm. Second Geological Survey, Delaware, 

 Part. I., C. 0. 



largely by edaphic conditions. Thus the for- 

 est type exists where the geologic formation 

 is covered by a surface layer of soil of some 

 depth. The barren treeless formation exists 

 where the serpentine rock is exposed with 

 little or no surface soil. Where springs occur 

 and the soil is wet, the character of the asso- 

 ciations is determined by the amount of soil 

 water. 



A. Serpentine at Glenriddle, Pa. 



The barren above Chester Creek at Glen- 

 riddle along the road leading from that place 

 to Lima is distinguished by the dominance 

 of Quercus stellata Wang. [Q. minor (Marsh.) 

 Sarg.],* Quercus nigra L. [Q. marylandica 

 Muench], Quercus alba L., Acer ruhrum L., 

 Juniperus virginiana L., Ca^tanea sativa Mill, 

 var. Americana Gray \_Castanea dentata 

 (Marsh.) Borkh.], Sassafras officinale Nees 

 [S. sassafras (L.) Karst.], and Gornus florida 

 L. (Mixed Deciduous Formation Juniperus- 

 Acer-Nyssa-Quercus Association). The sec- 

 ondary species beneath the shade formed by 

 the above-mentioned are Rhus glabra L., Vi- 

 burnum dentatum L., Yaccinium stamineum 

 L. [Polycodium stamineum (L.) Greene], 

 Gaylussacia resinosa Torr. & Gray [(Ait.) 

 Torr. & Gray], Yaccinium pennsylvanicum 

 Lam., Yiburnum acerifolium L. and Salix 

 tristis Ait. The lianes, or climbing plants 

 that festoon the trees, are Vitis cestivalis 

 Michx., Smilax rotundifolia L., Smilax glauca 

 Walt., Rhus toxicodendron L. [R. radicans 

 L.]. The herbs found here are Hieracium 

 venosum L., Pieris aquilina L. [Pteridium 

 aquilinum (L.) Knhn], Antennaria planta- 

 ginifolia Hook. [(L.) Richards], Baptisia 

 tinctoria R. Br. [(L.) R. Br.], Rubus trifiorus 

 Richardson [R. Americanus (Pers.) Britton], 

 Potentilla canadensis L.,~ Rumex acetosella 

 L., Veronica agrestis L., Hypoxis erecta L. 

 [H. hirsuta (L.) Coville], and Lysimachia 

 stricta Ait. [L. terrestris (L.) B. S. P.], all 

 species iisually found in dry situations like 

 the sandy pine barrens of New Jersey. In 

 fact, there is a striking similarity in the floras 



* Names according to Gray, sixth edition, with 

 names in parenthesis according to Britton's ' Man- 

 ual of the Flora of the Northern States.' 



