274 BOTANICAL GAZETTE [octosex 
V. VARYING ECOLOGIC CONDITIONS AND RESULTING DISTRIBUTION 
OF MEMBERS OF THE SOCIETY. 
Plainly the conditions on the upper surface of the riprap extensions 
become less xerophytic n passing downward toward the swamp 
below, and also because the riprap is not so high toward the lower 
ends. The gradual increase in amount of moisture influences per 
ceptibly the distribution of the lichens upon the riprap extensions. 
Biatora myriocar poides is more prevalent toward the upper portion 
of each extension, not because it is poorly adapted to the more moist 
conditions farther down, but because in the latter position the plant 
must compete with others as well or better adapted to the position. 
The Amphiloma-like hing, in its distribution upon the riprap, shows 
a most delicate adjustment to conditions of moisture. At the lower 
ends of the extensions it is more common, rises to the exposed ik 
face and forms a conspicuous portion of the flora; while in passing 
upward, it becomes less and less conspicuous, and toward the upper 
ends is scarcely noticeable on the exposed upper surfaces of the 
blocks, but is frequently seen in crevices and increasingly so the : 
deeper one may be able to look downward through the loose riprap- 
Bacidia inundata occurs on the northward-facing wall and competes 
with the last for position upon the upper surface toward the lower 
ends of the extensions, but from its inconspicuous character and Ie 
frequent occurrence does not form so conspicuous a portion of 
society. The Cladonias also are most delicately responsive t0 MO 
ture conditions in their distribution in the society (fig. 3)- — 
the lower ends of the extensions, they rise to the expo : il t» 
the riprap, and in passing upward are more and more case 
seek the more moist and shaded positions in the cracks betwee® 
blocks of riprap and along the sides of each riprap extensil © 
toward the base of the wall. It has already been noted neg 
moisture reaches the upper surface toward the upper “ — 
the extensions are higher, and it may be added here that ee lower 
surfaces are more exposed to the drying winds than those at the 
ends of the extensions and nearer the level of the general s of the 
ing surface, this condition also influencing the distribution 
Cladonias. 
