(195) 
p.271. Th. Fr. Gen. p. 92. Schismatommatis sp., Mass. Ric. p. 57. 
Lecanactidis sect., Stizenb. Beitr. 1.c.p.156. Mull. Principes de 
Classif. p. 67. 
Apothecia rotundata oblongaque, excipulo proprio margine ple- 
Tumque occulto 1. obsoleto, accessorio thallode coronato. Spore 
ex oblongo fusiformes, quadri-pluriloculares, incolores. Spermatia 
oblonga |. bacillaria; sterigmatibus simplicibus. Thallus crustaceus, 
uniformis. 
That a mere name, based on a lichen far from representative of the 
group before us, as developed at its proper centre (Schismatomma, Flot. 
& Koerb. 1. c. 1848) extended next to cover almost the whole of Lecanactis 
(Schismatomma, Mass. 1. c. 1852) as more lately substituted for Lecanactis 
(Schismatomma, Mudd, 1. c. 1861) and characterized only in 1855 (Schis- 
matomma, Koerb. 1. c. & Parerg.) when it is referred to Lecideacei, should 
invalidate the definite Platygrapha, Nyl., of the same year, is certainly 
a difficult conclusion for those who have learned from the writer last 
named to estimate the real extent and significance of the group. The 
elucidation of Platygrapha is in fact due to Nylander; who, alone of 
lichenographers, has pursued, and defined it, in its tropical home. Rep- 
resented, at the extreme north, by but a single lichen, only two others of 
the twenty-five species extend beyond the tropics, in the eastern hemi- 
sphere; one reaching from the Canaries and Portugal to Shropshire in 
England, and the other occurring in Algiers. And our own P. ocellata is 
in like manner, properly, a tropical species. 
P. periclea (Ach.) Nyl. (Schismatomma dolosum, Flot. & Koerb.). 
On Hemlock bark, New Bedford, Mass. (Mr. Willey; the fortunate finder 
of a long-desired plant).——P. Californica (Tuck.) Nyl. in Syn. Lich. 
NV. Caled. p. 58, not. (Dirina, Tuck. Lich. Calif. p. 17). On the bark of 
Oaks and Pines, California (Mr. Bolander). With the whole habit, and, 
it may be added, structure, of a Lecanoreine lichen, and resembling not 
a little a common Californian condition of Lecanora glaucoma, this might 
well seem referable, and by the evidence at once of the hypothecium, the 
spores, and the spermatia, to Dirina; but I can have no hesitation in 
accepting the emendation of Dr. Nylander, and referring it to the present 
genus. The series of affinities which enables us to connect the lichen 
—in spite of its alien habit, not qualified by any details of structure 
looking definitely in the present direction—with Graphidacei, takes 
its start however, it is evident enough, from the tropical centre of the 
group; from such types as P. dilatata, and P. leucopsara, Nyl. (Lindig 
Herb. N. Gran. n. 2887) and by no means from the outlying and depau- 
perate P. periclea. Spores of P. Californica 0,016-0,018™™ long, and 
0,003-0,004™™- wide. ——P. ocellata, Nyl. (Lecanactis punctillum, Tuck. 
inlitt.). On Beech trunks, and on Berchemia, in the low country of South 
