(97) 
(C. C. Frost). Lime-rocks in Missouri (E. Hall). Sufficiently remote 
from typical conditions of ZL. Tremelloides ; but its characters are much 
the same with those of plants perhaps not easily to be kept apart from L. 
Tremelloides, v. microphyllum. Collogonidia mostly solitary and scat- 
tered without order in L. ductylinum; but they also occur in short strings 
of three to six. 12. L. crenatellum, a eakbas Suppl. 2, 1. ¢. p. 200. 
Trunks, Vermont (C. C. Frost). Spores *2?nmm., always in fours in the 
thekes; the longitudinal series of spore- -telly four. 13. ZL. pulchellam 
(Ach.) Nyl. Syn. p. 123. Collema corticola, Tayl. Leptogium, Tuck. in 
Lea Catal. Ohio. Trunks, and rocks. New England, and southward to 
Virginia, common. Ohio, (Lea). Mountains of Carolina and Georgia 
(HB. W. Ravenel). Alabama (T. M. Peters). Texas (C. Wright). Ill 
described, and surprisingly compared with Collema pustulatm and C. 
nigrescens, with the latter of which it is placed, in his sect. Lathagrium, 
by Acharius. JL. cimiciodorum, Mass. (Anz. Lich. Venet.n.14. Herb. 
Krempelh. Rabenh. Lirh. Hur. n. 762) scarcely differs in any respect 
from the American lichen; whichis certainly close also to the next species. 
Spores of L. pulchellam > ammm.; the longitudinal series of spore-cells 
oftener six.——14. ZL. Tremeiloides (L. fil.) Fr. Rocks and Trunks. 
With the species last preceding we enter the at length extraordinarily 
modified group which has its centre in the tropics. The present is how- 
ever by no means confined to the warmer regions of the earth; extend- 
ing, in less perfect forms, very far northward, and reduced at length, 
here, to conditions scarcely at all recognizable. At the extreme south 
(Alabama, J. F. Beaumont; Mississippi, Veitch) smooth, wider-lobed forms 
oceur, best comparable with v. azureum (Sw.) though rather inferior in 
size and colour; and even, as we come north, at length (South Carolina, 
H. W. Ravenel) sparingly isidiophorous. In Lousiana (Hale) the passage 
of v. azureum into v. foveolatum (Leptogium, Nyl.) appears also to be 
represented. At the north (New England and middle states, as in 
Europe) a smaller and less regularly-lobed, often complicate form, beset 
more or less, or at length quite covered with isidioid branchlets —v. 
cyanescens, Ach., prevails; and this occurs also at the south (Louisiana, 
Hale). Much more difficult are the reduced forms—v. microphyllum (L- 
juniperinum, Tuck. Suppl. 2,1. ¢. p. 200) occurring on rocks and upon the 
earth, in New England and New York; in Tennessee (H. W. Ravenel) 
and in Texas (C. Wright) the very near relation of which even to L. 
minutissimum becomes finally (Illinois, E. Hall) almost conceivable, and 
to L. dactylinum, Tuck., certainly probable. In the larger, tropical forms 
of this species (v. azurewm) the spores are often also larger than in the 
northern lichen, and reach in the v. foveolatum (Venezuela, Fendler) even 
anmm. as the longitudinal series of spore-cells are increased to eight 
and ten; but these figures, like the thalline characters of the plant, illus- 
trate only an extreme of evolution, and differences not to be depended 
13 
