82 Rhodora [Mav 
do follow the Great Lakes, serve to point the path by which these 
plants must have travelled. Consequently I have thought it not 
too extraneous to place in the list at the end of this paper, the coastal 
plain types in the Mohawk-Hudson Valley and Ontario Basin, 
whether or not they reach the Great Lakes. It gives me pleasure to 
acknowledge the kind assistance of Prof. Wiegand in preparing this 
part of the work. 
The connectives through central Ontario and the Ottawa River 
Valley, which are so conspicuous on the map of the Algonquin stage, 
are not well known to me in their floristic aspects. But the Ottawa 
Valley has at least a few coastal plain species to show, such as Juncus 
pelocarpus, Utricularia resupinata!, Elatine americana?, Carex exilis), 
Sporobolus uniflorus*, and Isoétes riparia. 
And lastly, the sand dunes of the Illinois River, of which we are for- 
tunate in possessing a catalogue of the flora’, have about eight true 
coastal plain species. A glance at any of the maps of the glacial 
lakes will show that the Illinois River functioned as the outlet for Lake 
Chicago during all the period of which we are speaking. "This outlet 
was, judging from geological evidences, a broad and deep one, lined 
on its sides by many local sand deposits. It is hardly necessary to 
state that the presence of some twelve coastal plain species there is 
in part due to the migration along the shores of the glacial lakes and 
their outlets. 
In the case of the Illinois River, however, as in the case of its trib- 
utary the Kankakee, it must be remembered that they have probably 
been open to more than one coastal plain influence—that is, since 
they have at different times been connected with the St. Lawrence 
Basin and with that of the Mississippi, they perhaps owe the origin 
of their coastal plain'elements to both valley systems. Thus such 
plants as Rynchospora corniculata and its variety interior, have prob- 
ably reached Illinois and Indiana by way of the Mississippi Valley and 
not by way of the Great Lakes. This may be inferred from the fact 
that these plants are found today well up in the Mississippi Basin and 
are not found across the Great Lakes shores. To the same path of 
migration Mikania scandens probably owes its presence on the Kanka- 
! Macoun, Proc. & Trans. Roy. Soc. Can. xii. 30 (1894). 
? Fernald, Ruopora, xix. fig. 12 (1917). 
* Fernald, Proc. Am. Acad. xxxvii. 482 (1902). 
* Macoun, Ottawa Nat. xxiii. 192 (1910). 
5 Gleason, loc. cit. 
