HARSHBERGER: PHYTO-GEOGRAPHIC SKETCH 137 
Ambrosia trifida and Sagittaria latifolia (Fic. 3, BBB), in other 
areas this forms pure associations (Fics. 3, 4, 2) and in still other 
situations it is mixed with Cicuta maculata (Sagittaria-Cicuta 
association) (Fic. 3, /°). Cephalanthus occidentalis always occurs 
in the drier soil of the tidal marshes and in a number of places 
r ; 
peiaware aan Little Tinicum Jd, 
e IG. 1. Map showing position of tidal-marsh region surveyed, Thearea traversed 
'S represented as the dotted portion of the map. The area surveyed ecologically is 
represented by the portion designated by the oblique lines (V). The area of the 
eauies (P ) enlarged in figures 2, 3, and 4 is inclosed by the heavy lines. The easil 
fon of the Scirpus association is shown at Q. The open river marsh (not diked ) is 
Indicated, as also the location of the high ground. 
With it grow Cornus Amomum Mill. (Cornus sericea L.), Sambucus 
Canadensis L., (Fic. 2, S), Stachys palustris L. and Convolvulus 
sepium L.. (Calystegia Sepium L.) (Fic. 3,). Alluvial islands occur 
in the channels of the streams. These are at first covered by the 
Spatterdock, and as the soil becomes drier through the building 
action of these plants, the spatterdock is replaced by other plants, 
