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Geographical Distribution of Indigenous Plants. 61 
Alisma plantago, var. americana | Carex maritima (N). 
) Carex canescens (N). 
' Vallisneria spiralis. Carex buxbaumii (N). 
Juncus effusus (N). Carex fulva. 
Juncus auriculatus (N). Carex extensa. 
Eriocaulon septangulare (N). Carex riparia (N). 
Eleocharis palustris (N). Carex paludosa. 
Eleocharis acicularis (N). ; Leersia oryzoides (N). 
Scirpus pungens (N). Alopecurus aristulatus (N). 
Scirpus supinus, var. hallii. Spartina juncea. 
Scirpus maritimus (N). Spartina stricta. 
Scirpus sylvaticus (N). Glyceria fluitans (N). 
Rhyncospora alba (N). Glyceria maritima (N). 
Carex gynocrates (N). Glyceria distans(N). 
Carex norvegica (N). Phragmites communis (N). 
Carex salina (N). 
The plants of this list, as noted at its head, alllive either entirely in 
the water, or else in swamps, marshes or wet places. We know that for 
some reason or other, all forms of life inhabiting the water, are more 
cosmopolitan. than terrestrial forms. Fishes, aquatic reptiles, fresh- 
water shells, water mammals, and wading or swimming birds, are all 
more generally distributed over the world than terrestrial species of 
the same classes. So, too, it is with plants. These have many facili- 
ties for migration, which other forms of life have not. Not least 
among them is the chance of their being carried in the mud, adher- 
ing to the legs, feet, and bills of aquatic and wading birds,* which 
often range over extensive tracts of country. The water communica- 
tion existing between the northwest coast of America, and the valley 
of the Mississippi, forms a natural highway for the migration of aquatic 
plants. The Yukon, the Mackenzie and its tributaries, the Red river 
of the North, the Mississippi and its tributaries, the Great Lakes 
and the St. Lawrence, form an almost uninterrupted water-way from 
Asia to the United States, and it can not be considered remarkable 
that 63 out of these 89 water plants have a northern extension, at least 
as far north as 90 deg. latitude. Of the remaining 23, some special re- 
marks must be made. 
Nuphar lutewm, the first on the list not found north of latitude 50 
degrees, has been found but once in America. “ The only specimen 
seen like European “form,” says Gray, “was from Manayunk, seven 
miles below Philadelphia.”+ Now,as the variety pumdlum, also a- 
native of Europe, has a northern extension, it is probable that the 
single specimen may have been introduced in some way, especially as it 
was found soclosetoa largecity. Carex norvegica has also been found 
* See Darwin, Origin Species, 6th ed., p. 328. 
+ Gray’s Manual, p. 57. 
