132 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
simple or rarely branched, commonly enlarged and brownish toward the apex; asci 
clavate or cylindrico-clavate; spores as in the first species, or sometimes a little 
narrower. 
Collected on Oak Island in Lake of the Woods and on Grand Portage Island. On 
earth over rocks. 
Found in mountainous regions in the United States, as the mountains of New 
England, the Rocky Mountains, and Mount Hood (Oregon), and in the mountains 
of Mexico. Also generally distributed in British America and Alaska. Known also 
in South America, Europe, and Asia. 
EXPLANATION OF PLATE 19.—Plant on rocks; a top view giving an undue depressed appearance, but 
showing the much-branched podetia covered with phyllocladia and the apothecia. Natural size. 
PILOPHORUS Th. Ir. Ster. Pil. Comm. 40. 1857. 
The thallus, like that of Cladonia and Stereocaulon, consists of primary and second- 
ary, but the primary is very poorly developed, consisting of a verrucose crust which 
is so inconspicuous and evanescent that no account is usually taken of it in descrip- 
tions of species. The podetia forming the secondary thallus are simple or very spar- 
ingly branched. The central portion of each podetium is composed of a loose network 
of hyphe, which may fill the whole center of the cylinder, or may be absent from the 
axial line, leaving the podetium hollow at the center, Immediately surrounding 
this central portion is the mechanical lissue, consisting of densely packed. hyphe 
extending longitudinally. The podetia are without cortex and are clothed more or 
less with phyllocladia containing the algze, which are of the genus Cystococcus, 
The apothecia are small or of medium size and are globose, subglobose, or elongated. 
They are terminally disposed upon the podetia and are black externally. The hy- 
menium is also black and very tough and stout. The paraphyses are black or bluish 
black tipped. The spores are hyaline, simple, ellipsoid or fusiform. 
The genus differs from Stereocaulon mainly in point of the dark and tough character 
of the apothecia and in having simple spores. ° 
A single species has been found in the State. 
Type species Pilophorus robustus Th. Fr. op. cit. 41, 
1. Pilophorus cereolus (Ach.) Tuck. Syn. N. A. Lich. 1: 235. 1882. 
Lichen cereolus Ach. Lich. Suec. 89. 1798. 
Podetia erect, rigid, cylindrical or subcylindrical, simple or rarely bearing 2 to 5 
branches, clustered or scattered over the substratum, short and stout or more slender 
and elongated, 5 to 40 mm. long, the apex often subulate in sterile specimens, solid or 
rarely hollow; phyllocladia minute, rounded or becoming flattened and squamule- 
like, sea-green to ashy or rarely olivaceous; apothecia about 1.5 mm. in diameter, 
subglobose; spores fusiform, 17 to 20 fe long and 5 to 7 » wide. 
Ours is sterile and the apothecial and spore characters are taken from Nylander. 
Collected on rocks at Grand Marais. Not previously reported from Minnesota, 
Widely distributed in the northern United States and British America. Known 
also in Asia, Australia, and Africa. 
Family COLLEMACEAE. 
This family is one of the best defined groups of lichens, being quite distinct from 
any other group, both in the structure of the thallus and in the character of the algal 
symbiont. | 
The thallus is foliose, but either has no cellular cortex or possesses a single layer of 
cells above and one below. Nor are the internal layers well differentiated, the algal 
cells being scattered throughout the thallus, except in the single-layered cortex when 
this structure is present. In all of ours the algal symbiont is a form of Nostoc, and the 
heterocysts are easily made out. The thallus is more or less gelatinous when wet in 
all of our species, a condition due to a swelling of the gelatinous sheath of the algal 
