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solutumve, e collogonidiis1. varie dein aggregatis 1. seepissime monil- 
iformi-concatenatis et in pulpa mucilaginosa nidulantibus, constans. 
As respects the fructification there is no question that the great bulk 
of the groups before us is Parmeliaceous; and their anomalies of thalline 
structure have also, it should seem, not to be questioned Parmeliaceous 
points of departure. Careful comparison of the whole structure of such 
a series of lichens as Pannaria rubiginosa, P. fulvescens, and P. lurida, 
Collema byrseum, and Leptogium myochroum (L. saturninum, Dicks., & 
Auctt. pl.) and its allies, or of such a series as Pannaria tryptophylla, 
and P. flabellosa, and the species brought together in Lecothecium, Ptery- 
gium, and Collolechia of authors, indicates, if I mistake not, far from 
doubtfully, that these are series, not of plants of mixed classes, or of 
lichens of mixed orders, but of types variously modified of what is most 
readily conceivable as the same tribe. Pannaria lurida, Nyl. (Collema, 
Mont.) is assumed, on very high authority, to be, on the whole, congener- 
ical with P. rubiginosa; and Collema byrseum (C. byrsinum, Ach., 
Physma, Mass.) belongs, with as little doubt, to the higher groups of Col- 
lemei: but the congruity of structure in the first-and last-mentioned of 
these lichens is significant; and precludes, here, any distant separation 
of them. 
It is the more or less gelatinous nature of the larger proportion of the 
Collemei, when wet, that has always attracted the attention of observers, 
from Micheli (Gen. p. 87) and Dillenius (Hist. Musc. p. 187-147) to 
the present day (Koerb. Syst. p. 394) and this, in itself however useful 
yet certainly subordinate distinction, suggested without doubt the long 
prevalent views of an essential diversity of structure in these plants 
(Lichenes thallo extus intusque homogeneo, Ach. L. U. p. 129, t. 14, f. 8. 
Lichenes homeomerici, Wallr. Naturgesch. d. Flecht. 1, p. 225) which 
later and more thorough investigation has by no means confirmed. This 
asserted difference in structure was yet far, at first, from being regarded 
as sufficient to exclude Collema from that place (among Lichens) to which 
the sum of its affinities referred it. Acharius grouped the genus with 
Parmeliaceous types, as did Floerke, Wahlenberg, Sommerfelt, and Fée; 
and Eschweiler vindicated for it the same position : while Meyer, Wallroth, 
and Scherer (Spicil.) refused to recognize in it anything higher than 
marked sections of their Parmelia and Patellaria. 
Nor did Fries, in his earlier expositions of the Lichen-system (in Vet. 
Ak. Handi. 1821, & Sched. crit.) depart from the view that Collema is 
Parmeliaceous. We find here Biatora, Collema, Parmelia (in its largest 
sense) and Peltidea (in the same) making the first series of the highest 
division (Hymenothalami) as later (Syst. Orb. Veg. 1825) Collemacei, in- 
cluding Ephebe, make the last tribe of the same division.’ In the work 
1 In the imperfect but often instructive sketch of the system as conceived by 
Prof. Naegeli(Hepp Flecht. Eur. Taf. 1.) Collemece take a similar place, as the last 
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