136 HARSHBERGER : PHYTO-GEOGRAPHIC SKETCH 
Hibiscus Moscheutos L., occur, with occasional patches of the senst- 
tive fern, Onoclea sensibilis L. Along the edges of the stream- 
banks in the shallow water grow Clinopodium vulgare L. (Cala- 
mintha Clinopodium Benth.), /Jussiaea diffusa Forsk. (J. repens 
Sw.), Sagittaria latifolia Willd. (S. variabilis Engelm.), Czcuta 
maculata L., Ludwigia alternifolia L., Stachys palustris L. and 
Asclepias incarnata \.. In the deeper water fringing the shore 
of the creeks, strips of wild rice, Zizania aquatica L. (Zizanta 
association) and of Nymphaea advena Soland. (Nuphar association) 
are found. 
The tidal marshes of the rivers Delaware and Schuylkill are 
extensive and may be in places one half a mile wide (Fic. 1). 
Several well-marked zonal areas of marsh vegetation are notice- 
able in making an ecologic survey. Some of the marshes have 
been diked. Others at high tide are flooded with water, and yet 
the ecologist can distinguish relative depths of water by the 
character of the vegetation alone (Fics. 2, 3, 4). If one begins 
with the open channels of the creeks and ditches that intersect the 
marshes, the following zonal areas can be distinguished. In the 
deeper water along the channel, the reed-grass, Z7zania aquatica 
(Zizania association) forms the outer fringe of vegetation (FIGS. 
2, 3, 4, A, AA) and where it does not occur Nymphaea advena re- 
places it and forms a pure growth (Vu/har association) (FIGs. 2, 
3, Z). In July two colors of reed-grass are noticeable: a dark 
green mature form in deep water (Fics. 2, 3, 4, 4) and a light 
green immature growth of reed-grass inside of the dark green area 
(Fics. 3, 4, 4d). In the shallower water behind the reed-grass 
and spatterdock several associations of plants are seen. One area 
(Fic. 2, /) is characterized by the commingling of Sagittaria lati- 
folia, Impatiens biflora, Ambrosia trifida, Nymphaea advena, with 
an occasional association of Hibiscus Moscheutos (Fic. 2, H) and on 
the drier area Sambucus Canadensis (Fic. 2, KKK, KKKK), Cepha- 
lanthus occidentalis, Parthenocissus quinquefolia, Rubus nigrobaccus 
and a few willows, Salix alba (Fics. 2, 4, W ). In other areas (Fic. 
2, O) Impatiens biflora, Rudbeckia laciniata and Sagittaria latifolia 
occur, and on drier soil (Fic. 2, 17) Thalictrum polygamum and 
Heracleum lanatum. As shown in Fic. 3, D, Typha /atifolia 
forms a pure association (7)pha association) surrounded by 
