— 22 
Concerning the present species, the variety alpha, cribosa of Wainio, is 
plainly the species, including nearly all specimens within our territory, and 
being the most common by far according to the distribution given it by 
Wainio. Also after looking through the species yet to be considered in this 
series of papers, it is apparent that there will be no difficulty in following the 
method inaugurated in the present paper, while the explanations given 
above regarding the species disposed of in previous papers of this series will 
clear up any difficulties, and enable workers to use this portion of the series 
in the same manner as the papers to follow. 
The feeling that a change must be made has been growing as studies of 
the Cladonias have progressed, and defense for the procedure is ample. We 
may not be able often to ascertain elementary species by taxonomic methods, 
but we should at least make our systematic species conform as nearly as 
possible to the biological species. In so doing we must employ the parallel- 
istic method of considering both form and function in the selection of our 
spectific marks, when two morphological characters are equally prominent, 
giving more prominence to the one that is more useful. Then, too, if we 
are ever to approximate to true species, we must use some definite criterion 
and come to some agreement as to chief differentials. The statistical method 
proposed by Davenport and Blankinship, in a recent joint paper, seems to the 
writer to contain much of suggestion. We must not be content to base our 
views on a few herbarium specimens, but modes or centres of variation 
must be established in the field, by examining a multitude of specimens., 
then we must determine ranges of variation and degree of isolation for vari- 
ous forms encountered before deciding upon the limits of species and vari- 
eties. And nowhere is this sort of study more necessary than in the variable 
and plastic Cladonias , By this method, a worker may established species 
and varieties in the areas studied with some degree of mathematical cer- 
tainty. Then, by comparing results of such work in various regions, we may 
hope to establish world-wide conceptions of species of much greater value 
than those of the present time, discarding many of the “ historical types,” 
which are doubtless in many instances not true species, but varieties instead, 
and establishing true or “specific types.” De Vries has given instances in 
which systemists have found the elementary species, or at least true biologi- 
cal species, as opposed to compound conceptions, and we may hope by 
proper methods to approximate and often realize such results. 
While the results to follow in this series of papers must rest upon the 
study of herbarium material very largely, no pains will be spared to make 
the species and varieties recognized conform as nearly to true biological 
species as can be done. 
Cladonia cariosa (Ach.) Spreng. Linn Syst. Veg. 4: 272. 1827. Primary 
thallus persistent or replaced by new squamules, composed of irregularly 
laciniate, incised or crenate, concave, flat, involute or revolute, ascending or 
suberect, clustered or rarely scattered squamules, which are small or medium 
sized 1-6 mm. long and 1-5 mm. wide, pale sea-green above, varying toward 
olivaceous, whitish below or brownish toward the base, the cortex continuous 
