Review 
103 
The book is divided into ten chapters, dealing with the history of 
lichenology, the algal and hyphal constituents of the thallus, the 
morphology of various types of thallus and associated structures, the 
methods of reproduction, the physiological aspects (including an account 
of the chemical substances formed by the cells), the bionomics of dura¬ 
tion, dispersion and parasitism, the probable phylogeny of the various 
groups, the classification and distribution, the ecology, and finally the 
economic and technical uses. In the last chapter many interesting, 
though obsolete, uses are quoted. The only use (except for litmus) to 
which one has seen lichens put in the south-west of England is wreath¬ 
making, and this is not mentioned. Usneas are the chief lichens used, 
but Ramalinas and Evernia prunastri are also employed. Cladonia 
rangiferina is referred to on p. 401 as the “favourite food’’ of the rein¬ 
deer. One may be pardoned for suspecting that it is their favourite food, 
only because it is Hobson’s choice. Zopf’s statement (quoted on p. 400) 
that reindeer absolutely refuse to eat Cladonia sylvatica is rather 
misleading. If they are able to distinguish between C. rangiferina and 
C. sylvatica, they are cleverer than most lichenologists. 
The table of contents is a special feature and occupies twelve pages. 
It gives full information on the sections treated in each chapter, thus 
acting as a guide to the student seeking information on a special point, 
and leaving the index free for a list of the authors and plants referred to 
in the work. 
The author often gives the views of other lichenologists and states 
the evidence on which these views are founded, without committing 
herself. When she expresses her personal views, they appear to be sane 
and safe ones, which harmonise with a broad and general knowledge of 
the subject. Much of the work has been done by specialists; sometimes 
by a field-worker with little experience of experimental work, at others 
by a laboratory worker who has concerned himself little with the natural 
conditions under which the plants grow, so that his work with artificial 
cultures may have only a specious value. The author’s knowledge of the 
various parts of lichenology, in addition to her studies of micro-fungi, 
has enabled her to coordinate and correlate the work of such specialists 
in an efficient manner. 
Much of the work on nutrition discussed on pp. 39-43 is incomplete 
or unconvincing. Most of the nutritive experiments were carried out 
with Xanthoria parietina, or some other lichen, which prefers situations 
where organic material is abundant. The results of some of the experi¬ 
ments merely prove that the separated symbionts prefer a good diet to 
what is a starvation one for them, but one on which many lichens are 
able to exist. The occurrence of lichens in alpine situations, on more or 
less vertical rock-faces, can scarcely be analysed by artificial methods 
of growing the separated gonidia or hyphae in comparatively rich 
nutrient solutions. Lichen hyphae are stated on p. 47 to be usually 
thicker-walled than those of a true fungus. If this were a constant 
“spot” distinction the difficulty of distinguishing between a lichenoid 
fungus and a fungoid lichen would be simplified. The view that the fungus 
is parasitic on the alga, which has been recently revived by Elenkin, 
receives no support. Any lichenologist knows that penetration of the 
algal cells by the fungus is an unusual occurrence, and, though empty 
algal cells are often frequent, they are much less frequent than in a 
scraping of Protococcus taken from a tree-trunk. 
The alterations of the algae, particularly of Scytonema and Trente- 
pohlia, when they become symbiotic partners with fungal hyphae, is 
well expressed on p. 62. In the case of Placynthium nigrum the alga 
seldom shows its proper character; sometimes it appears like a Tolypo- 
thrix, but more often it is still less like Scytonema. The algal cells in 
