1922] CURRENT LITERATURE 
Rather closely related to the consideration of reproduction stands that of 
phylogeny in another chapter. This opens with a presentation regarding the 
algal hosts, which many would omit from a consideration of the phylogeny 
of lichens. Following this is a valuable treatment of the relationships between 
lichens and other fungi from the standpoint of evolution. The evolution of 
the thallus is considered next, then that of the various groups of lichens. The 
chapter closes with a ‘scheme of suggested progression in lichen structure.” 
e chapter on taxonomy considers first the various schemes of arrange- 
ment, following which the lichens are arranged according to the system of 
ZAHLBRUCKNER, as given in ENGLER and PrantL. Then follow treatments 
of number and distribution of lichens, with a survey of the lichens of polar an 
temperate regions, and fossil lichens. Probably ZAHLBRUCKNER would modify 
the classification outlined fifteen years ago considerably, were he to give his 
present views; but it is readily conceded that no lichenist, save perhaps 
Warn10, has shown so much skill and knowledge in the classification of lichens. 
For one who believes that lichens are dual organisms, there is no other possi- 
bility than to consider them a distinct group of plants, as is done in the volume 
before us. Also, as a matter of expediency, lichens may be treated separately 
by those who believe that they are fungi, although at the expense of failing to 
present adequately the many close relationships between lichens and other 
fungi. In any flora which covers all fungi, distribution should be made some- 
what as is done in papers by the reviewer and several other American bot- 
anists. 
The chapter on bionomics contains a valuable discussion of the growth and 
duration of lichens, the season of fruit formation, dispersal and increase, 
parasitism, and the diseases of lichens. Closely related to this is the chapter 
n ecology, which brings together for the first time a considerable portion of 
the material which deals with this subject. Although the research on lichen 
ecology is mainly pioneer work and much of it faulty, the worker in this phase 
of ecology must refer to the chapter, which will be bewildering to many who 
have concluded that lichens are fungi. 
ile SCHWENDENER and other Europeans have held that lichens are 
fungi, they have not been able to treat lichens as fungi after the method of 
mycology in general. This has been left to America, where the more rational 
treatment of these plants began to take form a generation ago and is now 
taught in a considerable number of institutions and believed by many teachers 
and other botanists. The reviewer does not relish attacking the conception 
of lichens held by the author of a work of great merit. The issue is unavoidable, 
however, and although American botanists may get much of value from the 
volume, it is to be hoped that students will not be taught that lichens are not 
plants, but yet in some mysterious way are plants, and that maturer botanists 
may be able to get that which is valuable from the work and not fall into the 
confusing phraseology regarding the nature of lichens.—Bruce FINK. 
