ECOLOGY OF WOODLAND PLANTS. 337 
first map (fig. 1, p. 338) indicates the distribution of the dominant 
trees, the dotted areas showing the distribution of shade trees, 
chiefly Sycamore (Acer Pseudo-platanus), Elm (Ulmus montana), 
and Beech (Fagus sylvatica). The lines show the distribution 
of Oak. A few other species are indicated by signs. 
In making a primary examination to determine the shade- 
areas, photographic printing-paper was used. 
A piece of printing-paper was exposed to bright light for 
ten seconds and this was used as a standard... This shade (as 
seen through the glass to be used) was copied as carefully as 
possible in oil-colour and then cut up into small pieces. Printing- 
frames were made of 3 x 1 inch glass slips backed with opaque 
paper in such a way as to form envelopes or pockets with glass 
fronts. A piece of the standard colour was pushed down to 
the lower end of the pocket, the upper half receiving a strip of 
printing-paper. The frames when filled were taken into the 
wood and a preliminary test made in the open; then a set was 
exposed simultaneously in the area to be examined, and a record 
taken of the time required to print to the depth of the standard. 
A somewhat similar but more elaborate method was devised by 
Wiesner (107), but his paper did not come to my notice until 
after these observations were made. 
Considerable differences were found under the same species of 
tree in different parts of the wood, owing to the condition of the 
tree, the mode of its growth, closeness of planting, and the like. 
Again, the “ Mosaic” of illuminated and shaded areas under the 
tree introduced another disturbing element and made it difficult 
to indicate in numbers the precise amount of shade produced for 
a given species; but so obvious was the difference between 
groups of trees composed of Acer, Ulmus, and Fagus on the one 
hand, and those consisting.of Quercus and Betula on the other, 
and so frequently did these species occur in masses together, 
that to indicate the former as a “ shade "-area and the latter as 
a “ light "-area gave a useful working basis. 
Cieslar (12) has shown, by using Wiesner's method, how great 
is the effect of shade on the production of humus and in in- 
fluencing the number of species occurring under a given tree. 
He was, however, working under the very uniform conditions 
of planted Beech forests of determined ** Durchforstungsgrad,” 
and numbers under these conditions could more easily be given. 
The next step was to map the undergrowth, and after several 
