— 4 — 
tion of the Cetrariae in the Tuckerman herbarium. The plant was collected 
in Central Point, Oregon, by Mrs. Agnes Ashworth, and as we are informed 
by Mrs. Carter, grew inmixtwith Everniavulpina . While the thalline char- 
acters were obviously those of Cetraria. patient search on our part failed to 
find a specific name. A portion of the specimen sent to Prof. Fink drew a 
statement that it was new to him, “ that it seemed nearest to Cetraria Rich- 
ardsonii ,” although he was not sure. In May, 1905, through the kindness of 
Prof. John Macoun, we received a suite of the lichens collected by him during 
the summer of 1904 in the Rocky Mountains. No. 7 of the set from Glacier, 
British Columbia, found on bushes, proved to be like the Oregon plant above 
mentioned, except a better specimen. Prof. Macoun had marked the packet 
Cetraria scepincola , but admitted a doubt of the correctness. More search 
and study on our part still failed in satisfactory reference, and our final 
word in the interchange of opinion with Prof. Macoun was, that if Cetraria 
Islandica was known ever to grow on trees or shrubs, our plant might be 
that form. At a later date, gathering from Th, Fries, Lich. Scan. Pt. I. p. 
98, that small forms of the species were sometimes to be found on wood, we 
were quite prepared to find that Tuckerman knew the form, although this 
habitat was not mentioned in the Synopsis. The specimens appearing in 
Tuckerman’s collection all come from West America, and in addition to being 
marked C. Islandica have a qualifying sub-label “ aboricolaC It is not 
believed that the word is used to designate a particular variety or form of 
C. Islandica but merely as descriptive of its habitat. This opinion is borne 
out by Tuckerman’s frequent use of “ aboricola ” throughout his herbarium 
to designate corticoline forms. Unlike the Umbilicaria of our first topic, 
which presented no divergence from normal appearance, this plant varies not 
a little, as may be seen by comparison of the appended description with 
Tuckerman’s a. 
Cetraria Islandica (L.) Ach. 
*M. arborialis (conditional nomination). 
Thallus cartilagineous, foliaceous, sub-erect or now appressed ; lacinae 
plane, variously and irregularly divided, the apices commonly obtuse, from 
narrowed to sometimes four mm. in breadth, very smooth and shining or 
sub-opaque : greenish-olivaceous or olivaceous-fucescent, the margins of the 
lacinae either spinulose or not, in the later case sometimes white- sorediate. 
Apothecia not observed. 
The lacinae seem to be held to the twigs not by rhizinae, but by an 
obscure adglutinated intergrowth. No trace of the sanguineous color char- 
acteristic of the basal portion of the type plant is observed. The resemblance 
of the plant to some forms of C. ciliaris is sufficiently marked to suggest the 
thought of its being factorial in the phylogeny of that species. It is rather re- 
markable that Tuckerman gave no space to the form, and it might be taken 
that he considered it of no importance. However this may be, the plant 
varied sufficiently in habit to be extremely puzzling to the writer, and on 
present evidence diverges enough from the normal presentments of C. Island- 
ica to be regarded as a distinct form. Rockland, Maine. 
: M= modification. 
