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remains still structurally diverse from Nostoc-like Alg@, and associable 
with the better-characterized, and still more evidently lichenose, Ameri- 
can species. 
And it is not enough that we touch here plants of another Class; or 
that even the difference in thalline structure which distinguishes 
E.. pubescens from these might, at least conceivably, be accounted for by 
mycelial cells of a parasitical fungus infesting the intercellular spaces of 
a Sirosiphon, Kiitz. (De Bary, l.c. p. 269). It still remains true that 
E. solida exhibits commonly and abundantly that well-defined modifica- 
tion of the Parmeliine apothecium which characterizes Synalissa and 
other Collemeine lichens; while in structure, however this be simpli- 
fied, it recedes from the latter in a direction indicating affinity to higher 
(Lichina — Pterygium— Pannaria) rather than lower types; and that 
E. pubescens is substantially, in everything except its abnormal fruit, 
congenerical. 
The observations of Bornet (1. c., & in Mém. Cherb.) upon Ephebe and 
the closely related Spilonema, Born., were followed by those of Nylander, 
who has illustrated also (Sym.) the common relations of both to Thermu- 
tis, Fr. (Gonionema, Nyl.) and even, by associating with these, in his 
Lichinei, not merely Lichina but his Pterygium, to what must be regard- 
ed, from the point of view of the present treatise, as a higher than Col- 
lemeine type. But we find here (Nyl.1.c.) the structure of Thermutis 
(Gonionema, Nyl.) less perfectly characterized: and it was left to 
Schwendener (Flora, 1863, 1. c.) to shew that as respects as well the 
gonidia (instructively exhibited already by Hepp’s figure, above-cited) as 
the filamentous elements, Thermutis is really no less lichenose, or more 
‘Scytonematoid,’ than Ephebe. ‘Dillwyn well remarks,” says Harvey of 
his Scytonema ocellatum (Man. Brit. Alg. p. 154) “ that it is most nearly 
allied to Stigonema atrovirens; and it seems indeed to be intermediate 
between Stigonema and Scytonema, the division of the sporidia” (gonidia) 
“in old filaments, assimilating it to the former genus.” And Flotow, 
comparing (1. c.) in like manner, the young extremities of Ephebe and 
the thallus, as he understood it, of Thermutis, and these with the older 
portions of the first-named type, could regard both, —the apothecia of 
the last only being then known, —as referable to states of but a single 
species. Alike in both lichens, and in Spilonema, Born., as well (Schwend. 
1. c.) the tips of the thallus exhibit, under the microscope, a simple, axial 
row of collogonidia, exactly as in Scytonema; and this gonidial column 
breaking up then into ‘transverse rings,’ the older portions assume, in 
like manner, the internal structure of Stigonema. Not however without 
a very important difference. As Nylander expounded Ephebe, it was 
scarcely to be questioned that we had before us a true lichen. And 
Schwendener has shown that that irregular parenchyma which comes at 
length to occupy the centre of the oldest thallus as a medullary, and in 
this way to give character to the gonidial elements as now in some sort 
9 
