78 Rhodora [APRIL 
which gradually modify and enrich the soil, thus paving the way for 
higher plants. Those here discussed seem to be all species which 
take very little nourishment from the soil, and some of them (the 
Sarracenias, Droseras, Pinguiculas and Utricularias) depend on the 
animal kingdom for a part of their sustenance. 
On examining the ranges of these plants it will be noticed that a 
few of them do not extend very far inland in the glaciated region, but 
whether this has any special significance or not it is difficult to say. 
Quite a number which were formerly thought to be confined to the 
vicinity of the coast have since turned up near the Great Lakes, in 
the upper Mississippi valley, or at other interior points. The great 
gaps in the known ranges of some are surprising, but may be due 
only to imperfect exploration. 
The origin of species having ranges like those above described is 
an interesting question. During the Pleistocene period the glacial 
region and coastal plain were both uninhabitable (one being covered 
with ice and the other with water) and before that their soils were 
very different from what they are now, so it is almost certain that 
most of the species at present chiefly confined to those regions have 
originated since then. The few which now occupy isolated stations 
in the Piedmont region and southern mountains may of course have 
been there before the Pleistocene, but it seems more likely that they 
have migrated there in comparatively recent times from the regions 
where they are now much more abundant. 
The glaciated region, like the coastal plain, doubtless has its own 
endemic species, but to attempt to enumerate them would be beyond 
the scope of this paper, and would require more knowledge of that 
region than the writer possesses. 
All the above remarks are intended to be merely suggestive, rather 
than exhaustive and the list here given can doubtless be considerably 
extended by further study. With the increased attention that bot- 
anists are now paying to geography we may reasonably expect a 
great deal of new light on the subject in the near future. In tracing 
ranges for phytogeographical purposes care must always be taken 
to discriminate against introduced plants, whether introduced from 
foreign countries or from other parts of the same state. In few local 
floras is such a distinction made. The Nymphaeaceae and some 
other aquatics are particularly liable to appear in new localities 
through the indirect agency of man, establishing themselves readily 
in artificial ponds and ditches outside of their natural range. 
