296 BOTANICAL GAZETTE [APRIL 
undrained swamps, ¢. g., peat bogs. Schimper even goes so far 
as to regard peat bog plants as xerophytes, because the humus 
acids in the soil make it difficult for plants to obtain the requisite 
amount of water. Consequently peat bog plants have worked 
out xerophytic structures to reduce the transpiration. All of the 
swamps at Dune Park are undrained swamps, and may be called 
potential peat bogs. The chemical nature of the soil is such that 
the plants have doubtless adapted themselves to all of the essen- 
tial conditions of a xerophytic life. The partial burial of these 
plants by a dune results, as has been seen, in no rapid change of 
relations with the water in the soil. The aerial organs, however, 
are exposed to a greater degree of light and heat by reason of 
their proximity to the sand. Thus the tendency to transpiration 
is increased, but the plants may be able to keep it within bounds 
through the xerophytic structures that have already been worked 
out in a swamp environment. It is likely, too, that these yee 
tures become more and more xerophytic as a result of life on 
and in the dune. 
The theories that have been exploited in the preceding pate 
graph find, at least, a partial confirmation. The leaves of the 
three successful species have more or less pronounced = 
phytic structure. The leaves of the dogwood are quite strong) 
pubescent. The willows, however, are more decidedly xero- 
phytic. The leaves of Salix adenophylla are very haitys mn 
the cuticle is thick. Salix glaucophylla has leaves with pet 
thick cuticle, and coated on the under surface with Ps a 
layer of bloom. In the dune form of this latter species 
leaves are notably thicker and the bloom more dense. It ; the 
author’s intention to make a careful comparative study i pe 
anatomical characters of these plants, and make report ere 
second part of this paper. All three of the species a on 
above have a remarkably wide range of habitat, oceuttt ae 
embryonic dunes, arrested dunes and heaths, as tk oe — alti- 
and on lee slopes. These shrubs may grow at a “a in 
tude and show a surprising independence of the pgs but 
the soil. There seems to be scarcely any doubt, there 
