FRANK C. GATES 
experimentation and the calculation of the results to a standard basis 
followed the normal methods used for such work. 
The object of this experimentation was the determination of the 
relationship between evaporation and plant succession in a local area. 
Douglas Lake region presents an admirable opportunity for such ex- 
perimentation. A detailed discussion of the vegetation of the area 
will be found in Gates (4). A brief resume of the pertinent facts is as 
follows: Aside from a few small associations, local along streams and 
around lakes, the vegetation of the region falls readily into three di- 
visions, each characterizing a soil type. Bog associations, particularly 
the Chamaedaphne, Larix, Picea and Thuja associations, occupy the 
low wet soil. The sandy uplands were dominated by the pine asso- 
ciation — now, following lumbering and fire, largely replaced by the 
aspen association. Clayey soil on the uplands is occupied by the 
hardwood or beech-maple association, except where it has been de- 
stroyed by lumbering or fire. 
Experiments were carried on separately with the vegetation of 
each soil type. The Thuja association, chosen for the bog experi- 
mentation, is typically composed of a large number of trees of Thuja 
occidentalism growing close together. The ground vegetation in a dense 
patch of Thuja is virtually nil. In open places, as along roads and 
trails, ericads and ericad-like plants are conspicuous. A few of the 
most abundant species are Ledum groenlandicum, Streptopus amplexi- 
folius, Moneses uniflora, Pirola asarifolia incarnata, Mitella nuda, 
Ruhus trifiorus, Cornus canadensis, Carex spp., Habenaria obtusata, 
Chamaedaphte calyculata and Vaccinium oxycoccus. 
The pine type — once represented by Pinus strobus and Pinus 
resinosa, now by scattering seedlings, small trees, and a few old trees 
of the same species mixed in with the aspen association — was investi- 
gated during 1915. At least 96 percent of the trees in the aspen 
association belong to the following four species: Populus tremuloides, 
Populus grandidentata, Betula alba papyrifera, and Prunus pennsyl- 
vanica. Among the higher shrubs are Salix rostrata, Rhus glabra, 
and Viburnum acerifolium; among the lower shrubs, Diervilla lonicera 
(which is frequently exceedingly abundant), Vaccinium pennsylvan- 
icum, Gaultheria procumbens, Rubus idaeus aculeatissimus, and Rubus 
allegheniensis are quite common. The fern, Pteris aquilina, is fre- 
quently more abundant than any of the shrubs. With the shrubs are 
seedlings and small trees of Quercus rubra, Acer rubrum, Acer sac- 
