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into a proper exciple. This defect notwithstanding, it is still the rudi- 
mentary proper exciple which is primary in Spherophorus, as in scarcely 
to be questioned relations of closest intimacy with Caliciacei; and the 
marked way in which the thallus of the former officiates as a partial re- 
ceptacle, must be explained from the point of view of the latter. In 
Lichina, on the contrary, the thalline exciple is what is essential; and 
there is nothing in this to separate it from known modifications of the 
Parmeliaceous type. 
Reference has already been made, in the preliminary remarks, to the 
important change in the systematic estimate of Lichina, which has fol- 
lowed the full explication of its structure; and Tulasne’s cited observa- 
tion in this direction, followed as it was by Nylander’s exposition of the 
close relations of the plants before us to his Pterygium (not easily to be 
deprived of its affinity to Pannaria) is now corroborated by the latest 
writer who has concerned himself with the question. ‘In view of all 
these facts,” says Prof. De Bary, ‘“‘ Lichina holds, in many respects, the. 
middle between fruticulose heteromerous and Collemaceous lichens.” ? 
And the significance of these certainly not superficial judgments, as 
respects both Ephebe, and its equally retrograde allies, as finally the 
whole question of an ordinal separation of ‘‘ Lichenes Byssacet,” will 
scarcely be doubted. If the highest structure of these ‘ byssaceous. 
lichens” be best comparable with that of Lichina, and if the structure 
of the latter associate it with types (Pterygium) only fully explainable 
from a Parmeliaceous point of view, the latter is then indicated as the 
true position from which to survey the whole group; and its retrograde 
members must follow those which determine it. In one series of Par- 
meliaceous genera (Cetraria, etc.,— Parmelia, — Lecanora, etc.,) there is 
indeed a marked structural diversity from Collemei in the gonimous 
system; but in another (Peltigera, etc.,—Pannaria) this diversity at 
length disappears, and all the conditions which make Collema an ultimate 
possibility, find, if we mistake not, their sufficient exemplification. 
There are two, now generally accepted species of this genus. The 
larger one, L. pygmea (Lightf.) Ag., is found on maritime rocks ‘ which 
are exposed and almost dry at high water’ (Hook.) through nearly all 
Europe, and as far north as the Southern provinces of Sweden and Nor- 
way. It is stated by Greville (Alg. Brit.) on the authority of Bory, that. 
D’urville met with this on the coast of Chili; but no other American 
station has been indicated. The other, LZ. conjfinis (Miill.) Ag., occur- 
ring on rocks ‘partially covered only at high tides’ (Hook.; ‘abi a summo 
fluru maris haud inundatur, sed tantum sub procellis ab undis marinis 
trrigatur, Wahl. Lapp.) extends throughout the same European countries, 
1“ Nach allen diesen Thatsachen halt Lichina in vieler Bezichung die Mitte 
zwischen den strauchartigen heteromeren und den Gallertflechten.’ De Bary 
Morphol. u. Physiol. der Pilze, Flechten, u. Myzomyceten, p. 268. 
