THE BRYOLOGIST. 
Vol. VII. 
January, 1904. 
No. if 
LICHENS— PELTIGERA. 
Carolyn W. Harris. 
The genus Peltigera is one of the most common among the lichens. 
While its range is generally northern, some species are found in all parts of 
our globe where conditions are favorable to their growth. In Europe and 
North America there are several species which are very abundant. Some 
of the Peltigeras resemble closely some species of Nephroma, but the fruit 
is borne on the upper side of the extended lobes of the thallus instead of on 
the under side as in Nephroma. 
It is very difficult to determine the different species when sterile because 
of the great similarity of the thallus. 
A well known lichenist says “it is impossible to do so with certainty.” 
The thallus is large, with rounded lobes, quite thick and soft when fresh, 
becoming brittle when dried. The color is bluish or brownish green, which 
changes to brown or brownish gray when dried. The lower surface is light 
brown, with conspicuous veining, and has usually long, hair-like rhizoids 
which cling so closely to the substratum, especially when growing on moss, 
that it is difficult to separate them. 
The apothecia are usually large and are terminal upon the extended 
lobes of the thallus. When young they are peltate, but in many species are 
revolute when fully developed. 
The different species of Peltigera are found on damp, mossy rocks and 
on the earth, often growing with mosses. They require a great deal of 
moisture; when dry they shrivel and become very brittle. After a rain 
when the cells are filled with water they unfold like a flower and are more 
than doubled in size. 
Peltigeras are supposed to be of rather slow growth and probably they 
are until they are well started, after that they increase rapidly. One I 
transplanted a year ago is now two thirds larger than it was at that time and 
is fruiting abundantly. 
No doubt many of the lichens which have been generally considered 
of slow growth have not been carefully observed for any length of time. 
Any one interested in the lichens having the opportunity of studying one 
particular specimen throughout an entire year, or even longer, and carefully 
keeping an account of its growth, fruiting, any change in form or color, would 
be doing an educational work. 
Peltigera venosa (L.) Hoffm. Thallus small, erect, ovate to fan 
The November Bryologist was issued November 2d, 1903. 
