220 
dams nearest the coast now seem to mark the dividing line 
between the pine-barren vegetation and that of the coast strip, 
especially in the case of water-loving plants. This accords 
very well with the belief recently expressed by. the reviewer* 
that pioneer aquatic vegetation is commonly associated with 
minimum seasonal fluctuations of water, and vice versa; for 
seasonal fluctuations are of course least just above a dam or 
shoal or waterfall and greatest just below, and these dams have 
probably been in existence long enough for the vegetation to 
adjust itself pretty well to such conditions. 
The vegetation of the pine-barrens, both upland and lowland, 
is distinctly of a pioneer type, with Pinus rigida the dominant 
tree. Among the less obvious floristic characters which dis- 
tinguish it from that of the neighboring regions are abundance of 
monocotyledons, Chamaecyparis, Rhynchospora, Gyrotheca, Lo- 
phiola, Utricularia (p. 689), Melanthaceae, Orchidaceae (361) 
and Ericaceae (617), and scarcity or absence of Equisetum, Pinus 
Virginiana, Juniperus, Carex (285), Hicoria (398), Fagus (403), 
Salix, Polygonum sagittatum (426), Ranunculus (455), Platanus 
(475), Crataegus, Impatiens (545), Viola, Liquidambar (474), 
Diospyros (634), Quercus Phellos (474), Prunus serotina (492), 
Cornus florida (602), минон native Cruciferae (462), Umbel- 
liferae, Labiatae, S fl (453) and weeds. 
(Almost the same michi be said ab some of the pine-barrens of 
the southeastern states.) In the list of characteristic pine-barren 
plants on pages 77-78, 47 per cent. of the angiosperms are mono- 
cotyledons, and there are 11 species of Ericaceae and Vaccinia- 
ceae. Nine of the 13 Melanthaceae mentioned in the catalogue 
grow in the pine-barrens, and three of them are confined to that 
region and one nearly so. 
On pages 81, 100 and ror the author points out that the Middle 
district is not а mere "tension zone" between the pine-barrens 
and the Piedmont region, as was recently supposed, but has 
enough characters of its own to rank equally with the pine- 
barrens as a distinct geographical division. It includes all of 
* Ann. Rep. Fla. Geol. Surv. 3: 234, 237; Bull. Torrey Club 38: 231-232; Torreya 
II: 233-234. Тоту. 
