HARSHBERGER : PHYTO-GEOGRAPHIC SKETCH 141 
aurea Muhl., Cardamine bulbosa (Schreb.) B. S. P., Drosera rotun- 
difolia L., D. intermedia Hayne, Sarracenia purpurea L., Myosotts 
palustris Withering, Mimulus ringens ., Cicuta maculata ae 
Fleracleum lanatum Michx., Lobelia syphilitica L., L. cardinalis 
L., Bidens laevis (L.) B. S. P., B. bipinnata L., B. Jrondosa L., 
Rudbeckia laciniata L., Eupatorium purpureum ., Heliopsis heli- 
anthoides (L.) B. S. P., Stachys palustris L., Alnus rugosa (DuRoi) 
K. Koch, Benzoin Benzoin (L.) Coult., Sambucus Canadensis L., 
Mex verticillata ( Li} Puc ‘Gray: 
The plants mentioned in the list fall naturally into several eco- 
logic associations. Thus, we have the Symplocarpus association, 
consisting of Spathyema foetida, Osmunda regalis, O. Claytoniana, 
0. cinnamomea, Cardamine bulbosaand Onoclea sensibilis. The Iris, 
Typha and Acorus associations are clearly demarcated. Herac- 
‘eum lanatum forms in swampy places a pure growth, as do also 
Veratrum viride and Lupatorium purpureum (Heracleum, Veratrum, 
Eupatorium associations). eliopsis helianthoides, Rudbeckta lact- 
mata, Commelina Virginica, Polygonum sagittatum, Mentha spicata 
and Vernonia Noveboracensis are usually together in aliuvial bottom 
lands at the mouths of streams where the soil is wet (Heliopsis- 
Rudbeckia association). In similar situations grow Solidago rugosa 
Mill, Hydrocotyle umbellata L., Carduus lanceolatus Hoffm, and 
Lobelia Syphilitica L. 
IXED-DECIDUOUS-FOREST FORMATION. — Originally the forest 
Covered most of the surface of southeast Pennsylvania. In some 
places, notably on the Wissahickon creek within the confines of 
Fairmount Park and in areas on Crum creek, the primeval forest 
still remains. Mr. J. Howard Lewis, Sr., and his progenitors have 
Preserved inviolate a large tract of timber along Crum creek, 
While the surrounding country settled by patent in 1681 and 1682 
has been cleared of its timber for many years. A study of such 
Preserves shows the character of the original forest. The domi- 
Nant and secondary forest trees grow on precipitous rocks, on 
declivitous hillsides, on the plateau surfaces left as a remnant of a 
°rmer peneplain, on the creek bottoms of the region, where the 
trees reach their largest size, and on the Delaware river plain 
down to where the forest formation merges with the river marsh 
Plant formation. All of the areas occupied by the cultivated-plant 
