FINK—THE LICHENS OF MINNESOTA. 107 
very similar apothecial structure. Hence it would seem that the Cladonias are closely 
related to Baeomyces. Plainly enough Stereocaulon is also closely related to Cladonia, 
and we need not discuss here several other closely related genera not found in our 
flora. 
Though the family consists of the single genus, this genus is the largest in our flora 
and contains nearly one-eighth of all of our lichens. 
CLADONIA Hill; Web. in Wig. Prim. Fl. Hols. 90. 1280. 
PLATE 11. 
The thallus consists of a basal more or less ascendant and squamulose primary por- 
tion and an erect fruticose portion, constituting the podetia. The basal or primary 
thallus may depart from the typical foliose and ascendant form, being then crustose 
and horizontal, and when so is more or less roughened or verrucose, In structure, this 
portion of the thallus shows a pseudocortex on the upper side, but the lower side is 
without cortex and usually sorediate; or more rarely the cortex is wanting even above. 
This primary thallus consists of squamules which are exceedingly variable in form and 
size even ina given species, and it may be evanescent, so that it is seldom seen in such 
long-lived plants as Cladonias. The algal and medullary layers are usually more or 
less differentiated. . 
The podetia commonly arise from the surface of the squamules or verruce of the 
primary thallus, though the primary thallus may disappear and even the bases of the 
podetia die while the upper portion continues to grow, perhaps for centuries. These 
podetia may be simple and cylindrical, tubeform, trumpet-shaped, or variously 
irregular, or they may be branched and are frequently very much so. Their summits 
are frequently cup-shaped, and from the margins or central portions of the cups sec- 
ondary podetia may arise, and from the cups of these tertiary, etc. These secondary 
and tertiary podetia are commonly called proliferations, and the lowest and original 
podetia form the first rank, the secondary podetia the second rank, the tertiary the 
third rank, etc. The podetia are thus in the form of more or less hollow cylindets and 
have the usual layers arranged radially. In both primary thallus and podetia the 
cortex is really a pseudocortex of interwoven and much gelatinized hyphx, and in 
the podetia algal cells are few. The cortex may be partly or entirely absent from the 
podetia, when they are likely to be sorediate. When present, the cortex may be con- 
tinuous, verrucose, areolate, or scattered-areolate. Squamules similar to those of the 
primary thallus frequently clothe the podetia to a greater or less extent. The central 
hyphe of the podetium run approximately in the direction of the long axis. The algal 
symbiont is Cystococcus. As to attachment, hyphal rhizoids are more or less frequent, 
fastening the squamules, or perhaps rarely the basal end of the podetia, to the sub- 
stratum. The squamules, and more especially the podetia, in these recently evolved 
lichens are so extremely variable that the Cladonias become the most difficult 
lichens to determine. 
The apothecia are either terminal on the podetia or on their cups or branches, or 
short apothecial stalks may intervene. They vary considerably in size, form, and 
arrangement, and may have a flat disk and a thin biatoroid margin, or a convex disk 
which is commonly without a marginal exciple. The prevailing color of the disk 
is brown or scarlet, and the upper portion of the hymenium usually partakes more 
or less of these colors, while the lower portion and the hypothecium are paler. The 
paraphyses are simple or more rarely branched, and the asci are clavate or cylindrico- 
clavate, with the apical wall almost uniformly more or less thickened. The spores 
are simple, hyaline, ellipsoid, and so uniform in size and shape that no use is ordinarily 
made of them in the classification of species. Soredia are very common, though incon- 
spicuous and easily overlooked. 
The genus is closely related, as already noted, to Stereocaulon; also to Tham- 
nolia, a genus consisting of a single species and not represented in our flora, 
