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pale, clothed at length with a white, perforated, irregular veil, in the 

 manner of many other species. Spores small, colorless, ellipsoid, 

 regularly and constantly diblastish ; the two opposite, conoidal sporo- 

 blasts being separated by a (not always visible) thin dissepiment ; the 

 length from once and a half to twice, or even twice and a half, exceed- 

 ing the width. Paraphyses conglutinate. The only described species 

 of Thelotrema with diblastish spores. Though the habit of the lichen 

 is sufficiently peculiar, and the little group to which it belongs (Myrio- 

 trema, Fee, Ess. p. 103, t. 1, f. 25 ; and Supph p. 92, t. 41, f. 1 - 3) is 

 distinguished also by the small size of its colorless spores, there seems 

 to be no good reason (as compare Montagne, PI. Cell. Exot. in Ann. 

 Sci. 3, 10, p. 131) for distinguishing it. 



GYALECTA, Ach. It was remarked by Mr. Turner, in describing his 

 Parmelia carneo-lutea (Linn. Trans. 9, p. 145), the apothecia of which, 

 he well says, "are very different from those of any other Parmelia, 

 and more resemble the apothecia of Urceolaria exanthematica" that its 

 place in the system " is that immediately following P. rubra." But it 

 was hot till 1852 that the two last-named species were brought together 

 in the same genus (^Gyalecta, Massal. Ricerch. p. 146), nor till 1857 that 

 G. carneo-lutea {Lecidea § Gyalecta, Nyl. Prodr. Gall. p. 101, n.) 

 was added to them. The group is an exceedingly difficult one ; but the 

 remark may be ventured, that however some species, scarcely to be 

 excluded from it, appear to pass into Lecidea, others are conditioned 

 by the thallus, or by other elements, in a way quite alien to Lecidea ; 

 while these differing subsections show obvious points of agreement in 

 the internal details of their fructification. The relation of G. rubra to 

 G. foveolaris, &c., is illustrated by Th. Fries in Lich. Arct. p. 138. 

 Acharius's type of Gyalecta (Lich. Univ. p. 29, t. 1, f. 7) was G. 

 epulotiea, since understood differently by Fries and later writers ; but 

 Ny lander (Lich. Scand. p. 189) adds this little-known lichen (of 

 which a fine specimen from Mr. v. Krempelhtiber is before me), 

 together with the nearly akin G. Prevostii, Fr., with apparently full 

 reason, to his section Gyalecta, — from the other species composing 

 which the two spoken of especially differ in their simple spores. The 

 contrast between such spores and the tetrablastish, and finally pleio- 

 blastish spores, which have been understood as characteristic of 

 Gyalecta, is however lessened by the intermediate differentiation of 

 the spores of G. asteria, described below ; and the genus, in this 

 respect, as well as in the variously modified external characters and 



