— IOI — 
[What is the form of the spermagones? Where are they situated on the 
thallus What is the form and size of the spermatia?] 
After the student has examined a certain number of species according to 
the above schedule he will have learned what to look for so well as to have no 
further need of such help, and will be able to make his preliminary examin- 
ations with thoroughness and rapidity. He will learn also that in dealing 
with certain genera, some features call for more particular observation and 
some for less. While it is desirable to know the microscopic structure, partic- 
ularly as regards the gonidia and the spores, it is not always necessary for 
the recognition of species and even to a less extent of genera, Hence a good 
beginning may be made with only a hand magnifier, which was indeed all 
the earlier lichenologists had to aid them. 
As regards the second difficulty referred to above, namely, that of not 
understanding fully the statements of the book or failing to make the neces- 
sary allowances, the student will find that these perplexities will disappear 
in proportion as the mind comes to associate the different phrases with partic- 
ular features seen in the specimens examined. As in the systematic study 
of other difficult groups, so with lichens, it is found to be very helpful at 
first if one can take specimens of which one knows the name, and compare 
them point for point with the description as given in the manual, for the 
family, genus and species to which they belong. To enable beginners to do 
something of this work, there is appended to the present paper a short 
analytical key by means of which the names of a few of our commonest and 
most easily recognized species may be determined with tolerable accuracy. 
In regard to the third mentioned source of difficulty (the variability and 
close resemblance of many species) it must be said that even the most 
advanced students have this to contend with, and as in the case of other 
perplexing groups, the last resort is the comparison of doubtful forms with 
authentically named specimens. 
Besides Prof. Tuckerman’s Synopsis the following writings in English 
may be profitably consulted by the student: 
An Introduction to the Study of Lichens. Henry Willey. New Bedford, 
1887. 
A Popular History of British Lichens. W. Lander Lindsey. London, 
1856. 
Guide to the Recognition of the Principal Orders of Cryptograms and the 
Commoner and More Easily Distinguished New England Genera. 
Frederick Le Roy Sargent. Cambridge. 1886. 
The article “Lichens” in Encyclopaedia Britainnica, Ninth Edition, 
and the Section on Lichens (pp. 114-126) in Gcebel’s Outlines of Classification 
(Oxford, 1887), give a good general idea of the structure, etc., of these plants. 
A Text- Book of General Lichenology, with Descriptions and Figures of 
the Genera occurring in the United States. Albert Schneider, Binghamton, 
N, Y., 1897. 
Such technical terms as occur in the following Key and have not been defined in the 
foregoing pages, are used in the same sense as when employed in the description of phan- 
erogams. The abbreviations are the same as those given in B'igs. 2-8. 
