1921] McW HORTER—MOSSES AND LICHENS CaaS 
The development of lichens in moss colonies makes possible the 
coming in of a lichen stage after the moss associations. 
Great obligation is due to Professor W. J. G. LAND for sug- 
gestions in regard to the technique used, and Dr. Gro. D. FULLER 
for aid in the preparation of the manuscript and for reading the 
proof. 
eke OF Cae eae 
Banos, P.I. 
EXPLANATION OF PLATE XIII 
The illustrations are all photomicrographs selected from a much larger 
sian showing similar conditions. 
1.—Cladonia pyxidata on moss, probably Dicranum; vertical section 
iat colony showing moss plant with leaves cut to pieces and apical growth 
stopped by action of lichen. 
Fic. 2.—Cladonia pyxidata on an unrecognizable moss; organization of 
moss leaves destroyed by action of lichen; lichen hyphae penetrated inter- 
rind through moss tissues. 
3.—Section of a moss-lichen mixture cut parallel to surface of colony, 
saeivine lichen (Cladonia) hyphae penetrated into cells of apical region of moss 
(Grimmia); hyphae indicated by arrow a could be traced through serial 
sections to lichen mass just above; 6, moss leaf strongly attacked by hyphae. 
Fic. 4.—Section from lower part of colony cut parallel to surface, ng 
lichen sels tending to fuse with pectinized walls of moss tissues. 
Fic. 5—Section through a Amphiloma-Grimmia mixture; Amphiloma 
has organized on moss leaf; this lichen probably destroys more moss than 
any other. 
Fic. 6.—Portion of fig. 5 more highly magnified, showing: a, how lichen 
may eotanletely destroy moss cells; 6. how hyphae dissolve pectinized layer of 
cell walls of moss. 
