FINK—-THE LICHENS OF MINNESOTA. 59 
nearer Dermatocarpon and related genera, there are submuriform conditions which 
seem to bridge over the gap between Arthothelium and Arthonia. 
Though the genus comprises about 50 species, only a half dozen are known in North 
America, and but a single one exists in Minnesota. 
Our plant is found only on trees. 
Type species Arthothelium spectabile Mass. loc. cit. 
Arthothelium spectabile Mass. Ric. Lich. 54. /. 101. 1852. 
Thallus mainly epiphloeodal and quite thick, whitish or grayish, sometimes in 
small patches, but more commonly covering large areas of the substratum, even 200 
mm. or more in diameter, frequently bordered or dissected more or less by dark 
lines, smooth or roughened or even subareolate; apothecia difform, angulate, oblong 
or variously irregular, often immersed in the thallus, black, plane or convex; hypo- ’ 
thecium brown or dark brown; hymenium brownish or brown; paraphyses much 
branched, hyaline or slightly brownish, the apices sometimes enlarged and more 
deeply colored; asci pyriform; spores ellipsoid, muriform, hyaline, or brownish, 8 in 
the asci, 28 to 38 » long and 10 to 16 wide. 
The plant has not been noted in the State, but is well known in northern Iowa 
and surely occurs in southern Minnesota. The species resembles Arthonia radiata 
externally and is easily overlooked. It is most common on hickory. 
Known more or less from the Atlantic to the Pacific and from Florida as far north 
at least as Newfoundland. Also found in South America, Europe, and Asia, 
Family LECANACTIDACEAE. 
The family is a small one and represented in our flora by only two genera, each 
represented by a single species, and these both rare or seldom noted. One of the two 
genera, Lecanactis, is northern in distribution and the other is southern. 
The members of the family all have a crustose thallus, frequently hypophlaodal 
and scarcely better developed than the thalli of the Graphidaceae. The algal sym- 
biont is likewise Chroolepus, and the members of the family are all transitional forms, 
closely related to the Graphidaceae as to thallus structure and perhaps more closely 
to the Lecideaceae as to apothecial characters. 
Both of the species assigned to the present family are sure to prove troublesome if 
found. The Melaspilea is likely not to be considered a lichen, as the thallus is 
frequently wanting. If taken for a lichen, it is likely to pass for a Lecidea or an 
Opegrapha. But the peculiar spores, consisting of two spheroidal cells should fix 
the plant. The Lecanactis is as likely to pass for a Bilimbia, but it may be known 
by its stronger, black, and persistent proper exciple. 
MELASPILEA Nyl. Act. Soc. Linn. Bord. 21: 416. 1856. 
The thallus is crustose, mainly hypophloodal, so giving a smooth and widely ex- 
tended crust, ashy in color, devoid of any differentiation into layers, the epiphloeodal 
portions at least quite commonly disappearing, in which case the thallus is said to be 
absent. The algal symbiont is Chroolepus-like. 
The apothecia are rounded or oblong, in the former condition appearing lecideoid 
and in the latter more like Arthonia or Opegrapha. They are, however, superficial. 
The disk is black and flat or convex. The proper exciple is also black. The spores 
are 2-celled, commonly hyaline, and oblong, obtusely ellipsoid, or slipper-shaped. 
Like Lecanactis, the present genus seems to be a transitional one with very similar 
relationships, the species having formerly been assigned to Lecidea, Opegrapha, 
Arthonia, etc. 
A single species has been found in Minnesota. 
Type species Melaspilea arthonioides (Fée) Nyl. loc. cit, 
