1904] PINK—A LICHEN SOCIETY 269 
somewhat less varied than those affecting the seed-plants surrounding 
the lichens. Yet for those more accustomed to the considerations 
of societies of these higher plants, a brief statement of the types of 
seed-plants will be more illuminating than would a mere statement 
of physiographic conditions and the corresponding structural adapta- 
tions of the lichens. So although the conditions affecting the lichens 
are somewhat different, we will no doubt be able to consider the lichen 
society more intelligently after such brief view of the higher plants. 
On the upper surface of the extensions and along the northward- 
facing riprap wall, the xerophytic conditions are plainly seen in the 
few scattered seed-plants, including Onagra biennis, Lepidium inter- 
medium, Ambrosia arlemisiaejolia, Cassia chamaecrista, Hordeum juba- 
lum, Polanisia trachys perma, Polygonum scandens, V erbascum T hapsus, 
and Cenchrus tribuloides. The same xerophytes occur on the dry 
gravel of the road bed with Equisetum arvense, Chenopodium Botrys, 
and one or two others; and in passing downward one encounters 
dry meadow, wet meadow, and grass-sedge swamp conditions, all 
in the few meters, the hydrophytic flora of the swamp showing a num- 
ber of large grasses and sedges, Cicuta maculata, Typha latifolia, 
Alisma Plantago, Scirpus lacustris, some forms of Sagittaria, and a 
number of fresh water algae in the limited areas where water stands 
a larger part of the time. 
Ill. COMPOSITION OF THE LICHEN , SOCIETY. 
That such rapid transition in seed-plant flora should be accom- 
andl similar conditions in the lichén flora would be 
the ee “hag miprap does not extend down to the swamp, and 
in their _ do not grow on the soil, or when they do they have 
the aa "i poor means for secking moisture as compared with 
seed-plants n eshy and deep-growing roots of some of the xerophytic 
by the “eee above. . Hence the lichens are not so much affected 
ingly the Sa as - soil moisture as are the seed-plants. Accord- 
entirely aa ure-loving Collemas, Leptogiums, and Pannarias are 
is shown in Bi : a extreme xerophytic adaptation as to lichen flora 
driest Portions His myrtocar poides, which grows abundantly on the 
t a. the upper surfaces of the riprap extensions, this 
ng in the more xerophytic lichen society what the 
