432 BOTANICAL GAZETTE [JUNE 
thalline differences are recognized beyond a certain plausible degree, it is 
hardly exaggerating to say we shall have eventually nearly as many genera 
as species. In fact in the present genus this is now almost true. In true 
Evernia prunastri, the type of the genus, a bifacial structure of the laciniae is 
evident. This condition becomes obscure in the variety thammodes, and in 
vulpina it is nearly radial. In divaricata the bifacial structure is about as 
in thamnodes, while in Trulla and true furfuracea it is markedly bifacial 
(parmelioid), but in the latter’s varieties (apical portions) ceratea and cladonia 
the radial structure is again approached. If a careful study of the thalline 
structure of the species here considered is made, it will be seen that the pen- 
dulous, prostrate condition of growth typical of this genus tends to destroy 
a complete radial development. A portion of some of the branches of almost 
every individual plant shows a bifacial structure, owing to the gonidia seeking 
the uppermost or light-exposed side. In the truly pendulous Usneas and Alec- 
torias, and wide branching, rigid, non-prostrate Ramalinas, and in the rigid 
cespitose species of the two former genera, the complete exposure develops 
a truly radial structure. In the present genus, it is not strange therefore 
that we find the luxuriant and more rigid examples of vulpina and the longest 
pendulous specimens of divaricata most nearly approaching the radial con- 
dition. In other words, so far as the sectional structure of the laciniae 18 
concerned, Evernia holds an intermediate position between the strictly radial 
Usneae and Alectoriae, and the bifacial Parmeliacei. 
The rare tropical lichen Evernia Trulla (Ach.) Mont. was set apart by 
NYLANDER in a unique genus, Everniopsis. I have been able to study but one 
specimen of this plant, kindly loaned me by the National Museum, and the 
scarcity of material thus precludes a sufficient study to settle satisfactorily 
the question of its classification in my own mind. There is no question that 
the plant morphologically is nearest to furfuracea, as TUCKERMAN pointed out, 
and its bifacial and membranaceous thallus can hardly be said to have 4 
chondroid axis, in fact a compressed stuppeous condition is all that appears to 
me evident. 
The striking similarity between the corniculate smooth Evernia furfuracea 
var. ceratea (Ach.) Nyl. from the highest alpine zone, and Parmelia physodes 
var. vittata Ach. is undebatable, and extends somewhat further than 4 mere 
superficial resemblance. In fact i hardly 
traceable, lying for the most part in the inflated laciniae, and ecanaliculate 
condition of the thallus. This striking similarity attracted the attention of 
YLANDER and CromBrE, and was perhaps the cause of the glossarial adjective 
“evernioid.”* There is every reason to hold this genus in close proximity 
to Parmelia.? Evernia (?Alectoria, Letharia) canariensis (Ach.) Nyl. shows al 
* NYLANDER, Flora 52:445-446. 1869. 
* Parmelia Camtschadalis var. americana (Mey. et Flot.) Nyl., except ins 
zinae, strongly resembles this variety, a canaliculate condition being here pres°"™ 
rhi- 
