206 PLITT AND PESSIN: ON DISTRIBUTION OF LICHENS 
9 to 10m. from Northwest Buellia parasema 764.64 c.c. 55% 
ground ecanora subfusca in 43 days 
Parmelia tiliacea 
Parmelia sulcaia 
IX Pertusaria multipuncta 
Ramalina canaliculata 
a 
Xanthoria parietina 
A study of the table seems to suggest that it is the evaporating 
power of the air that most affects the distribution of the lichens 
on the tree. It is true that there is some correlation between the 
intensity of the light and the distribution of the lichens, but this 
correlation is not as definite as that existing between the plant 
distribution found and the evaporating power of the air. It 
seems quite evident even from the limited data, thus far gathered 
that evaporation plays the chief réle in limiting the distribution 
of the lichens. Accepting this as a fact one can arrange the lich- 
ens found on this tree into four groups: Group I would include 
those lichens which inhabit only regions of relatively low evapora- 
tion. Thus, Lecidea vernalis, Leptogium tremelloides, Lobaria 
pulmonaria and Pertusaria amara would fall in this group. Into 
Group II would fall such lichens which inhabit regions of 
moderate evaporation. This group would include Conotrema 
urceolara, Arthonia radiata, Lecanora albella, Parmelia caperata, 
Parmelia physodes, and Lecanora varia. Into Group III would 
fall those lichens which are able to withstand dry conditions, 
and are found only in regions of high evaporation. Lichens 
included in this group are Pertusaria mulupuncta, Lecanora 
subfusca, Parmelia conspurcaia, Parmelia tiliacea, Ramalina 
canaliculata, Usnea florida, Usnea hirta and Xanthoria parietina. 
Group IV includes those lichens which seem to show no preference 
and are found in regions of high evaporation as well as in 
regions of low evaporation such as Buellia parasema. 
List oF LICHENS FOUND ON QUERCUS RUBRA AND THFIR DIs- 
TRIBUTION 
Arthonia radiata (Pers.) Th. Fr. 
The lowest level at which this chin was found was about 
four meters above ground in the northeast zone. No trace of 
it was found above eight meters from the ground. 
