16 
IOWA ACADEMY OF SCIENCES. 
very rarely of actual use in determinations. The so-called 
hypothallus is seldom seen and is of no use in the determi- 
nation of Cladonias, while those doubtful structures, the 
spermagones and the spermatia, may be likewise neglected. 
As to chemical tests, it is extremely doubtful whether they 
are of diagnostic value in any lichens; and in the Cladonias, 
even the spore characters are so constant that they may 
be neglected. Here is a condition favorable to the work 
on the Cladonias, and it must be added that there is not 
another lichen genus in which microscopic characters may 
be largely neglected in determinations. However, the 
Cladonias are a comparatively recent evolution, and the 
macroscopic characters are so extremely variable and the 
preserved connecting links so numerous that the determi- 
nations are extremely difficult. Indeed, instead of being 
able to trace anything like a continuous line of evolution 
or even an evolutionary tree, the best students see only 
an interminable network of forms. 
With all due respect to the late, eminent American 
lichenist, Tuckerman, it must be apparent to all who have 
attempted to use his diagnoses of American Cladonias as 
aids in determinations, that they are too brief and indefi- 
nite. For instance, Tuckerman recognizes in his manual 
just two varieties of Cladonia fiynhyiata, disposes of the 
species in a half page, and gives not the slightest hint that 
the forms are extremely varied and difficult to understand. 
This view is, however, all that could be expected from one 
who was a pioneer in the study of American lichens, and 
much as Tuckerman has done for American lichenology, 
we can not afford to do otherwise than pass beyond his 
results as rapidly as may be done with some sufficient de- 
gree of certainty. 
In a series of articles now appearing in the Bryologist, 
the present writer is attempting to give a more recent 
view of the Cladonias by means of adequate descriptions, 
illustrations and notes on distribution. However, this 
work is merely preliminary in nature and much remains 
to be done in way of actual examination of material in 
