452 BOTANICAL GAZETTE [JUNE 
lumina of its cells. In this respect bog herbs are all different from 
the bog ericads also. Among the bog shrubs the ericad type stands 
out distinctly from all the other shrubs, there being far less differ- 
ence between the structure of any two ericads than between an 
ericad and any other bog plant. 
Just how the water is conducted from the roots to the tran- 
spiring organs is not a closed question. For a discussion of it the 
reader is referred to the literature, 
particularly CopeLANp (5), Drxon 
(16), OvERTON (37), RENNER (41), 
SCHERMBEEK (43), and BABCOCK (1). 
The results of this investigation show 
that the fundamental control of rate 
of conduction is exercised by tran- 
spiration. An increase of transpira- 
tion always means an increase of 
conduction, and a decrease in tran- 
ste ee sienatiik of spiration means a decrease in con- 
the stem of Chamaedaphne caly- duction, though not always in the 
culata: the dark outer ring is cor. Same proportion. Absorption and 
tex, just within it is the medium conduction are more closely related 
nary Se to each other than to transpiration, 
center the pith. and they are more closely related 
to the turgidity of the cells than 
is transpiration. By reducing the turgidity of the cells transpira- 
tion exercises a control over the other two. 
UTILIZATION SYSTEM 
Although the external appearance of the leaves of various peat 
bog plants is very different, the general internal structure is more 
nearly similar, and that of the various ericads is still more alike. 
Several well marked xerophytic adaptations are present, notably 
the strongly cuticularized epidermis, absence of stomates on the 
upper surface, a well developed palisade layer one to three cells 
thick, frequently sunken stomates, and coatings of wax, bloom, 
hairs, or scales. Mechanical tissue is present and accounts for the 
suppression of the ordinary symptoms of wilting. Usually the 
