448 BOTANICAL GAZETTE [JUNE 
part of it is vaporized and passes out of the plant through the 
stomates. 
Xerophytic responses may be classified into means retarding 
transpiration in the leaves or transpiring organs, absorption in the 
roots, checking transportation in the conducting tissue, or pro- 
vision for an accumulation of water. In the peat bog ericads used 
during the course of this investigation, xerophytic response is very 
evident in the leaves, but is not accompanied by water storage 
tissue, which makes the xerophytic structure more necessary on 
account of the poorly developed root sytem. The evergreen habit, 
with its relatively large exposure of leaf surface, calls for greater 
activity of the root system throughout the winter, for transpiration 
still continues even when the thermometer is below zero. That 
means to reduce the loss of water are all the more necessary under 
winter conditions is obvious. 
Seasonal history of peat bog plants 
EVERGREEN ERICADS 
During the winter the leaves of all of the evergreen ericads: 
Chamaedaphne calyculata, Andromeda glaucophylla, and Vaccinium 
macrocarpon, are upright, a position in which they receive a mini- 
mum of direct sunlight. The leaves are dark red or brown in color. 
With the coming of spring the old leaves curve outward or down- 
ward, resulting in an increase of the direct sunlight which they 
receive. At the same time the leaves become dark green in color. 
The season’s growth of young leaves takes place soon after flower- 
ing. At first the young leaves are upright, but in a short time they 
bend outward. As soon as the young leaves are fully developed, 
the old leaves gradually drop off. In the case of Vaccinium macro- 
carpon, however, some of the leaves may be retained for two or three. 
years. With the coming of the next winter, the leaves of these 
plants gradually bend up into an upright position and their color 
changes from bright green through dark green to shades of red and 
brown. The color changes begin at the margins of the leaves and 
work toward the midribs. In a mild winter the basal portion of 
midribs of Chamaedaphne may remain green the entire winter. 
Vaccinium and Andromeda are usually protected by a covering of 
