- 42 — 
A practical difficulty in distinguishing between certain forms of Cladonia 
degenerans and Cladonia gracilis dilatata is mentioned below, and the 
writer has also had difficulty in separating certain specimens from forms of 
. Cladonia crispata. However, this difficulty will not often be met. 
It is certain enough that the two species considered in this present paper 
are not so closely related to each other, as is each one to some other Cladonia , 
but it is impossible, in the present state of knowledge of the genus, if at all, 
to place the Cladonias all in any probable continuous genetic series. 
F/g.l. 
Cladonia decorticata X2. 
Cladonia decorticata (Flk.) Spreng. Linn. Sust. Veg. 4:271. 1827. 
Primary thallus finally disappearing and usually more or less replaced by simi- 
lar laciniate or crenate. somewhat concave or involute, scattered or clustered 
squamules, which are usually small, 1-4 mm. long, and 1-2 mm. wide, light 
sea-green above varying toward olivaceous, below whitish or brownish toward 
the base. Podetia arising from the surface of the primary thallus ; 9-42 mm. 
long and 0.75-2 mm. in diameter; cylindrical, cupless, simple or more or less 
dichotomously or irregularly branched, the branches commonly erect or 
spreading; the fertile apices often dilated, the sterile ones obtuse or subulate: 
the sides sometimes fissured; clustered or subsolitary, erect or rarely ascend- 
