1911] BS ULLER—EVAPORATION AND SUCCESSION 201 
mesophytic forest dominated by the beech, Fagus grandifolia, and 
the maple, Acer saccharum. These two species form at least 85 
per cent of the tree growth, with the remaining 15 per cent com- 
posed of Tilia americana, Ostrya virginiana, and Prunus serotina, 
and occasional trees of Quercus rubra, Platanus occidentalis, and 
Liriodendron Tulipifera. The undergrowth is largely seedlings of 
the dominant tree members of the association, together with Cornus 
alternifolia, Viburnum pubescens, Asimina triloba, Sambucus race- 
mosa, and such herbaceous forms as Trillium grandiflorum, Dicentra 
JUNE JULY AUGUST |SEPTEMBER ocroser | 
2 j 
BS VATA | 
3 NY YI | 
= ie | Ne \N 
/ y AG 
T/T} M1 \ \ vs 
Bee ed FA 
—~ — | 
‘ Mee 
‘a — j 
J 
| 
Fic. 3.—Evaporation rates in the beech-maple forest association at stations 
nos. 11, 12, and 13. 
canadensis, Adiantum pedatum, Asplenium angustifolium, Poly- 
stichum acrostichoides, Viola rostrata, Impatiens biflora, Erigenia 
bulbosa, and Epifagus virginiana. As this represents the climax 
formation for a large portion of the United States, it was regarded 
as a standard to which other plant associations could be referred, 
and accordingly 3 stations were established in it on May 30, and 
maintained until the end of October, giving a continuous record 
for 155 days. On account of the difficulty in reaching these 
stations, readings were made only every second week throughout 
