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nellum. Nor would it be surprising, in view especially of Coniocybe, 
should species of Calicium be yet found to occur, the spores of which 
should be describable as colourless; but it is far from necessary to sup- 
pose a case in order to explain, as probably only decolorate, the colourless 
spores of Bryopogon ; facts sufficiently illustrative of this being by no 
means uncommon. And these facts, and others already touched, and to 
be touched upon hereafter, point not doubtfully, if we mistake not, to 
something like a rule, —that colour or the want of it being assumed to be, 
however important, an uncertain element in spore-history, and the ulti- 
mate or highest attainable condition of a type of spore being assumed to 
include, potentially, all the steps of the preceding process of evolution, 
such ultimate state may be expected to afford, in its total history, an 
index to the spore-modifications possible within the whole circuit of the 
natural group or genus to which the species furnishing the ultimate con- 
dition belongs. Buellia petrea and our B. oidalea are cases in point. 
Both offer the highest (muriform-multilocular) state of the brown type of 
spore, and, in the freely exhibited process of gradual evolution of this 
condition, both foreshadow or repeat every spore-modification conceivable 
within the limits of Buellia; and indicate as well the real, decolorate 
nature of some spores which, from a less comprehensive point of view, 
might well seem to be typically colourless. <Alectoria Loxensis (Fée) Nyl. 
(Lindig Herb. N. Gran. n. 2571. Oropogon, Th. Fr.) should seem then to 
be to A. ochroleuca much as Buellia petrea to B. coracina, in which last 
the spores (Moug. et Nestl. n. 462) are commonly simple; and the appa- 
rently colourless spores of Alectoria sulcata (Lév.) Nyl. (Syn. 1, p. 281, 
t. 8, f.20) should be as open perhaps to another explanation as the equally 
colourless but in fact decolorate ones of Buellia atro-alba, v. chlorospora, 
Nyl. (Catillaria, Koerb.). The general question thus opened, which is 
important in its bearing on the validity of many largely accepted genera 
of Massalongo and other more recent lichenographers, will be further 
considered in the progress of this work. Suffice it for the present to add 
that taking into account at once the spores of Alectoria nigricans, Nyl., 
as defined and figured by him (Lich. Scand. p. 71; Syn. t. 8, f.17) and 
the exceedingly close (if not questionable) relation in which the lichen 
stands, in every other respect, to A. ochroleuca, it will be as difficult to 
refuse to make it congenerical with the last, as, in that case, to exclude 
A. jubata, &c., from similar relationship. 
Of the eight species reckoned by Nylander (Syn.) four are common to 
the colder regions of the northern hemisphere, and one is peculiar as yet 
to North Western America. Of the other three, two are natives of the 
mountains of India; and the other of those of South America.——A. diver- 
gens (Wahl.) Nyl., is certainly far better comparable with A. jubata, a, 
bicolor, and A. ochroleuca, a, than with Cetraria aculeata ; notwithstand- 
ing a degree of external resemblance to the latter. The apothecia of this 
arctic lichen are very little known, and have been fully described only by 
