—go— 
ation of the various structures and their functions belong rather to minute 
morphology and to physiology. 
Finally in some lichens the so-called hypothallus is conspicuous to the 
eye or with the lens. This is true of some members of the genus Pannaria. 
For instance, in Pannaria nigra , this structure appears as a bluish-black 
ring all around the thallus. Its nature is not well understood, though possi- 
bly it is a remnant of some lichen that the Pannaria has over- grown. Some 
of the older authors considered the rhizoids a portion of the hypothallus. 
Conclusion. 
In these days of microscopes and microscopic study, there is some dan- 
ger that the beginner will actually come to think that there is little to be 
seen in lichens and other plants below the spermaphytes without using a 
microscope. The object of the present paper is, then, to call attention to the 
very many features of lichen-morphology which may readily be observed in 
the field, with no other aid than the eye, or this supplemented by a good 
hand lens. The points considered in the above pages are well known to lich- 
enists, but we do not know where they have previously been brought 
together in compact form so that the beginner may have them for ready ref- 
erence. 
It has not been possible to give, in so brief space, every feature of the 
gross morphology of lichens and all variations, but the statements are 
intended rather to be suggestive. It is believed that, if the student will 
repeatedly read the suggestions given, and then observe more carefully than 
ever before, he will soon become convinced that the lichens have more defin- 
ite features of gross morphology than he had ^ previously supposed, and that 
these features require careful attention at his hands. It is well known that 
a number of the readers of jthe !Bryologist are becoming interested in lich- 
ens, and it has seemed appropriate that such statements as are given herein 
should be brought to the attention of these persons as an aid to careful 
observation. Grinnell, Iowa. 
BOOK REVIEWS. 
SECOND EDITION DIXON & JAMESON. 
J. P. Naylor. 
A somewhat careful comparison of the last edition of Dixon & Jameson’s 
Student’s Handbook of British Mosses, with the Manual, Barnes’ Keys, and 
the file of the Bryologist, shows that, of the six hundred and two species 
described in the Handbook, four hundred and thirty-three are American 
forms. This is a little more than seventy-two per cent. Of the one hundred 
and fifteen genera all but six are found in the United States, and of these 
six, only one has more than one species. The British Moss flora seems to be 
particularly rich in one species genera ; there being forty-four of them which 
contain but a single species. 
The fact that the genera are so largely American, taken in connection 
with the plates and the admirable descriptions, makes the book most valu- 
