294 BOTANICAL GAZETTE [APRIL 
cafion walls is often entirely due to lichens, and in a general way 
they form the only brilliant plant formations in a landscape notable 
for its subdued, pale, monotonous tones. Most conspicuous are 
Acarospora chlorophana and Caloplaca elegans, which form striking 
landmarks when covering great crags and rock walls. The next 
most conspicuous lichens are Rinodina oreina and Lecanora rubina 
and its allies, which often entirely cover immense bowlders and 
northerly sloping rock walls. In places Gyrophora erosa and 
Gyrophora phaea may cover the rocks to the exclusion of other 
forms, but their dull brown shades are not at all conspicuous. 
Gyrophora reticulata is sometimes the sole occupant of northwest 
exposures, when its black thallus becomes quite noticeable. 
Candelariella cerinella and Acarospora bella are perhaps the only 
others which would attract the attention of the casual observer, 
nearly all the others having a dull or somber brown or dusky hue 
which blends in with the general rock color. 
The species of Dermatocarpon occur in crevices of rock walls, 
especially on northeastern and southeastern slopes, where they 
receive the maximum of protection from drying winds. The few 
small specimens of Physcia occur in the same localities, where they 
are very little or not at all exposed to direct sunlight. The re- 
maining lichens, except where previously noted, occur indifferently 
on all sides of bowlders or rock ledges, the sunniest and most arid 
of all possible situations, where one would hardly believe a plant 
could exist, being occupied by Gyrophora phaea and Acarospora 
thamnina. The largest and finest specimens of Gyrophora reticulata, 
as well as the best specimens of Lecanora rubina, are on northern 
or northwesterly exposures; this I attribute to the fact that these 
slopes are much colder, being exposed to the direct winds from the 
snow fields of the Sierras, and are also often covered for weeks with 
great snow drifts. 
With the exception of Lecanora rubina and its allies, few of the 
well exposed rock lichens could fairly be called foliose. The shor 
lobed species of Gyrophora hug the rocks as closely as possible, 
so that they are truly crustose except when in some sheltered crevice 
or more than ordinarily favorable position. The quite inconspicu- 
ous and sterile thallus of Parmelia exasperata and Parmelia glabra 
