Ig11] CURRENT LITERATURE 69 
America, for although it includes only the forms of a single state, the peculiarly 
wide distribution of species of lichens makes the bulletin really a manual for 
the determination of the lichens of the whole country. The bulk of the bulletin 
consists of the catalogue of species, but it is much more than that, for the species 
are described with a fullness and an exactness unusual in such descriptions, 
and convenient keys make the approach to genera and species seem simple 
enough. The numerous admirable reproductions of photographs also bring 
clearly to the student the field aspect of the different forms. 
There are 68 genera presented, comprising 314 species, and under the 
species there are often numerous varieties. It is of interest to note that the 
genera are not large, only 6 of them comprising 10 or more species, and the 2 
largest (Lecidea and Cladonia) comprising only 29 species each. This means 
that the remaining genera are represented on the average by about 3 species. 
- This is a striking illustration either of the constancy of lichen species over 
wide areas, or of the caution of lichenologists in recognizing variations as species. 
This is perhaps further emphasized by the fact that in the present publication 
not a single new species is proposed. 
The catalogue is preceded by a general account of lichens, so that the 
student of classification may obtain adequate information as to the morphol- 
ogy of the group. There are also some interesting paragraphs dealing with 
the economic réle of lichens, under the following heads: “‘as purifiers of the 
air,” ‘‘as aids in rock disintegration,” ‘‘as food,” “as medicinal agents,” “as 
dyestuffs,” and “‘as related to the welfare of trees.” 
This book should prove a great stimulus to the study of lichens, a group 
which deserves to be more cultivated by American botanists.—J. M. 
MINOR NOTICES 
Plant-breeding in the United States.—Professors v. RUMKER and v. 
TSCHERMAK have published a report’ of their extended American visit durin 
the spring and summer of 19009. e writers inspected most of the institu- 
tions in which either theoretical studies in genetics, or practical experi- 
ments in plant and animal breeding are in progress, as well as the work of 
numerous private breeders. The whole report forms an exceedingly keen 
The chapters close with full bibliographies. In the first part, which is 
occupied with American studies in genetic theory, full reviews are given 
of the newer work of SHuLL, CasTLE, Tower, Morcan, Macpovueat, and 
others. Part II, dealing with practical breeding operations, begins with 
an extended discussion of American experiment station investigations in corn 
breeding. The long-continued experiments at the Illinois station on the 
3 RUMKER, ag » Aint TSCHERMAR, V5 Landwirtschaftliche Studien in Nord-Amerika, 
mit besonderer gung iichtung. pp. 150. Berlin: Paul Parey. 
Tgio 
