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208 Rhodora [NovEMBER 
the water of practically the whole Basin, especially in dry seasons, 
but remains at the bottom of the river." 
The center of the marsh in question is about 4.8 miles above the 
dam, 1.5 miles above Western Avenue Bridge, and 1.75 miles below 
North Beacon Bridge. West Boston Bridge is nearly half a mile 
above the dam. "The surface of the marsh is from 3 to 5 feet above 
the level of the water, and is easily traversed. Innumerable ditches 
run east and west, some still open, others more or less closed, while 
still others are visible only by a slight depression on the surface. A 
ditch, interrupted here and there, skirts the western border of the 
marsh, while at the southern extremity an additional ditch extends 
northward for about one third of the length of the marsh. 
It seems clear from the above that no accession of salt water can 
now affect the marsh in question, owing to the permanent elevation 
of the surface above the river whose waters are pronounced practically 
fresh. "The retention of the salt still in the soil seems the determining 
factor governing the length of time that the true salt marsh plants can 
subsist. 
Before the closing of the river the flora of the marsh was typical 
of that of any similar area. Reference to my journals and herbarium 
shows that Juncus Gerardi Loisel. was the principal growth in 1884. 
Triglochin maritima L., Puccinellia maritima (Huds.) Parl. and Poten- 
tilla pacifica Howell were abundant. From this locality I also find in 
my herbarium Scirpus campestris Britton, var. paludosus (A. Nelson) 
Fernald, Atriplex patula L., var. hastata (L.) Gray, Ranunculus 
Cymbalaria Pursh, Gerardia maritima Raf., Solidago sempervirens L. 
and others, collected between 1884 and 1895. "These were taken on 
desultory visits and they represent only a few salt marsh plants, but 
as the specimens exist, they are worth recording. 
My recent visits to the marsh began in 1912 and have continued to 
the present time, though the principal work was done in 1912 and 
1913, covering the six months from May 1 to October 30. Thirty- 
one visits have been made, exclusive of some walks over the marsh 
when snow and ice covered it. 
I was first struck by the immense number of plants, both native 
and introduced, that had invaded the area from the neighboring up- 
lands and made a strange contrast with the plants growing there 
naturally. It seemed like the invasion of an army into a territory 
apparently little suited as a home for them, but they had evidently 
