ro14] GATES—XEROPHILY 457 
(L.) Moench, obtained from First Sister Lake, a little west of Ann 
Arbor, Michigan, and at Mud Lake in the northern part of Washte- 
naw County, Michigan. 
Toward the close of autumn in 1o1o0 and 1o11, plants of the 
evergreen ericads were potted and kept outdoors under prevailing 
conditions. During the middle of winter their transpiration was 
determined by successive weighings on a beam balance sensitive 
to 0.002 gram. The pot was inclosed by an aluminum shell 
(devised by GANonG) closed at the top with rubber dam and sealed 
with wax, whereby the water loss was limited to the plants, as 
controls repeatedly demonstrated. Readings of weight to 0.01 
gram, temperature by mercury thermometer and thermograph, 
relative humidity by wet and dry bulb thermometers, and general 
conditions of the weather were recorded. 
A number of pottings of ericads and other shits were made at 
First Sister Lake, June 1, 1912, the plants allowed to develop under 
bog conditions, and experimented upon the first week of July 1912. 
By far the greater part of the work, however, was conducted 
with cuttings. These were made from the plants at First Sister 
Lake, immediately cut under water in jars and brought into the 
laboratory where they were again cut under water. The cuttings 
were then set up in two-holed rubber corks in bottles of distilled 
water and sealed with vaseline. A thermometer inserted in the 
other hole of the cork gave the temperature of the water. Work 
with controls proved that the apparatus was water-vapor tight. 
Usually about one-half an hour was allowed for adjustment before 
measurements were commenced. Weighings were made at intervals 
of one, two, or more hours, according to the purpose of the experi- 
ment. Such experiments were seldom carried over 24 hours, except 
for special reasons. The day of 24 hours of 100 “‘minutes” each was 
used in recording experiments, because of its obvious convenience. 
Some plants which were transplanted into the greenhouse in 
Sphagnum did so poorly that no experiments were made upon them. 
Shoots that developed on cut twigs kept in water in the laboratory 
or greenhouse seldom lived more than a couple of weeks, and as 
their internal structure was not normal, no experiments were per- 
formed upon them. 
