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H. versicolor, H. endochroma, H. Domingense, and H. leucoxanthum ; 
which is precisely Heterothecium as finally accepted by Montagne. Among 
the species originally brought together in Afegalospora—the first con- 
ception of the genus, and, in some respects, possibly the purest —Lecidea 
sanguinaria was however included; and Flotow retained this, though 
‘mit unsicherheit, in bis later revision. For reasons to be given below, 
I shall venture here to take the same view of this difficult lichen; and 
cannot hesitate also to consider H. pezizoideum as in fact congenerical 
with H. leucoxanthum. 
Thus viewed, with the exception at least of the still doubtful Lecidea 
sanguinaria, and L. grossa, the group is a natural one, and is accepted 
as such by Nylander, who has largely illustrated it, and with whom it con- 
stitutes the last division of the first section of his Lecidea; or, as we 
should express it, the head of Biatora. From this last the present genus 
is distinguished (leaving out of account the mostly superficial, though 
often striking resemblance to Lecanora) by its spore-type: being really 
analogous in Biatorei to Physcia, in Parmeliei, Rinodina, in Lecanorei, 
and Buellia in Lecideei; though better comparable as a tropical group, 
and tending similarly to more varied modifications, and even anomalies 
of spore-structure, to the equally tropical Thelotrema and Graphis. In 
all these genera the spores belong (in great part manifestly) to that series, 
the ultimate modification of which is the muriform-multilocular; ex- 
pressed here by the section Lopudium, and in Buellia by the section 
Rhizocarpon. And such is the general affinity of the lichens brought 
together in the last-named groups to those which express in their spores 
the next preceding stage of differentiation (sectt. Bombyliospora, & 
Eubuellia) that the question has been raised already (Th. Fr. Lich. Arct. 
p. 226, & Gen. p. 92) with respect to Rhizocarpon, Massal., whether there 
is really reason for keeping it apart from Buwellia. Dr. Fries’s striking 
illustration from acolium, ‘the analogous genus of the Caliciacei,’ where 
A. Notarisii appears scarcely otherwise to differ from A. tigillare than as 
Rhizocarpon from Buellia, and that also from Rhizocarpon geographicum, 
Massal., the variety alpicolum of which is in fact a Buellia, are much to 
the point; and so too, if I do not mistake, is an analogous example from 
Arthonia, where A. cyrtodes, Tuck. (Obs. Lich. 1. ¢. 6, p. 285) presents in 
one form (Wright Lich. Cub. n. 245) otherwise specifically undistinguish- 
able from the other, spores similar to those of Bombyliospora, and in the 
other (Lich. Cub. n. 246) the mural-multilocular ones typical of this 
section of Arthonia (Arthothelium, Massal.) and of Lopadiwm. These 
observations apply equally to the section of the present genus with 
bilocular spores (Psorothecium, Massal.). 
Nor can the evidence of affinity afforded by general similarity of 
structure and habit be safely disregarded. This brings closely together 
H. Taitense, Mont. (Psorothecium, Massal.) and H. tuberculosum (Bom- 
byliospora, Massal.) and is so decided in the case of H. vulpinum (which 
