294 BOTANICAL GAZETTE [OCTOBER 
the apothecia being at least in part terminal, while in S. tomentosum they are 
said to be always lateral. Here again we have a variable character which 
cannot be used as a precise criterion. 
In searching for a character which would by its nature be mutually exclusive 
for the two species, the attempt was made to use the cephalodia. The differ- 
ences between the cephalodia typical of these two species are sufficiently indi- 
cated in the descriptions, to which reference may be made. To establish the 
taxonomic value of this structure, it was necessary to prove three points: 
first, both types of cephalodia must not occur on the same plant; secondly, 
the cephalodia must be constant enough in occurrence to be of use; and thirdly, 
the characteristics of the cephalodia must be correlated with the other diag- 
nostic characters. 
s has been shown by various investigators, the cephalodia of lichens are 
peculiar gall-like outgrowths formed by the hyphae of the thallus surrounding 
ing in the object sought. The results are given in the following tables: 
Number of Specimens examined «2. iS i wise tt tl CG 
Specimens with both types of cephalodia . . - . +: ° tT. 
Specimens lacking cephalodia. . . .... =. ce 9 
morris ini BORN a 
The fact that on only one specimen studied were both types of cephalodia 
found shows that for practical purposes the two types are mutually exclusive. 
Cephalodia being present in a larger proportion of specimens than were apothe- 
cia, it follows that if apothecial characters or spore characters are ot yas 
cephalodia can equally well be used, as far as constancy of occurrence 3S con- 
cerned. To show correlation of characters, the results may be arranged as 
follows: 
APOTHECIA 
CEPHALODIA 
Terminal | Mixed | Lateral 
omentosum type ¥3 28 
Paschale type....... II 18 | 2c 
