1922] Peattie,—Coastal Plain Element in Flora of Great Lakes 59 
lated “islands” of the coastal plain flora are likely to be encountered. 
Such "islands" are to be found along the Great Lakes and on some 
of the lakes of New York State. They also occur around Havana, 
Illinois, and at other points on the Illinois River, and there are var- 
ious small stations on acid bogs of the Middle West. The extensions 
of the coastal plain flora on the eastern sides of the Appalachians 
occur chiefly as arms reaching up high, abandoned, sandy flood-plains 
and are not anomalous, being directly connected with the coastal 
plain. Or such “islands” may occur as localized colonies in south- 
ern New England, Nova Scotia, eastern New Brunswick and New- 
foundland—a type of distribution with which we have not to do here. 
In the flora of the Lake Michigan area, at least, there are two 
general types of inland extension from the coastal plain. "The first 
type is the very discontinuous range. In many cases of this kind 
there are no known stations between the Atlantic coast and the south- 
ern end of Lake Michigan. Such a range is that of Eleocharis melano- 
carpa, which is mapped in Figure 1. This is not only typical for the 
coastal plain but for its *jump" or reappearance on the shores of 
Lake Michigan. About one third of all the coastal plain species of 
this area show a roughly similar range with, perhaps, one additional 
station in New York State or on one of the other Great Lakes. ` 
It is plants of this anomalous range which cause the greatest per- 
plexities to the student of plant distribution and it would indeed be 
hard to formulate any plausible explanation were it not for the coastal 
plain extensions of the second type. 
Figure 2 shows the range of Euphorbia polygonifolia. This little 
plant of the sea strands also occurs in a general way around the Great 
Lakes. Such a range is not so difficult to explain as the preceding 
type and is in itself highly suggestive of an explanation. The majority 
of the coastal plain species show a similar range. There exist all 
degrees of continuity between the Eleocharis melanocarpa type of 
range and that of Euphorbia polygonifolia. This makes it seem prob- 
able that whatever explanation of the second type of range may be 
offered will be equally well applied to the first type, since the differ- 
ence is only one of degree. 
