A HANDBOOK OF THE BRITISH LICHENS 181 



the key enabled me quickly to allocate the plant to its proper species. 

 The test was a severe one, as the lichens were Ramalina Curnowii, 

 R. breviuscula (which of course came under R. siliquosa, under 

 which it is placed in the Monograph of British Lichens as a sub- 

 species), Lecania prosechoides, L. pro&echoidiza, L. erysibe var. 

 sincerior, Lecanora polytropa, Lecidea latypea, L. protrnsa, Verru- 

 caria viridala, and Arthopyrenia stigmatella. In Bilimbia aro- 

 matica the spores in my specimen were rather larger than is given in 

 the key, but it was easily run down. The only case in which the 

 key failed was an unfair test — the plant was Ramalina subfarinaci a, 

 collected near Penzance from the branches of hawthorn, a very unusual 

 habitat; I have indeed seen no British record of it save from rods, 

 and had never previously noticed it on trees. As the key only takes 

 account of its saxicolous habitat, this anomalous plant was of course 

 difficult to place. The example will however serve to illustrate the 

 fact that there is no royal road to the determination of many species, 

 and that a supplementary use of the Monograph of British Lichens 

 is necessary for critical species and for those which are not exactly 

 typical in respect either of structure or habitat. Another example is 

 afforded by Ramalina farinacea ; the key relies on its arboreal 

 habitat, but it occasionally occurs on the sand of grey dune. To 

 include all such erratic characters is not the purpose of the Hand- 

 book, and such inclusion would destroy its portability ; one of 

 its great advantages is that it is convenient for carrying in the 

 pocket. 



The main part of the work is more than a key : much informa- 

 tion is given about the structure and ecology of the various lichens 

 and a typical species of each genus is figured. The classification and 

 nomenclature followed is that of the Monograph, of which any 

 criticism would here be out of place. Where generally-known 

 names have been superseded, the useful course of giving such names 

 in brackets has been adopted. 



The instructions on p. 13 in regard to the composition, use, and 

 interpretation of chemical reactions are too concise to be exactly 

 clear. The apothecium figured on p. 8 (reproduced from the 

 Monograph) conveys the idea that a biatorine apothecium has a 

 different internal structure from a lecideine one, which may not 

 be the case : a biatorine hypothecium often only differs from a 

 lecideine one in its external colour. The inclusion of algal cells 

 below the hypothecium suggests a lecanorine apothecium in which 

 the thalline margin has become obsolete. The rarity of t} r po- 

 graphical errors testifies to the care exercised in proof-reading : 

 on p. 54 subintricata should replace subimbricata, and a comma 

 has crept in between "Primary" and " thallus " (p. 71, line 3), 

 in the wonderfully active way that commas have— there seems 

 to be an affinity between them and their bacterial namesakes. 

 The statement that " Gladonia rangiferina " is the well-known 

 reindeer-moss ' needs a little amplification, owing to the difficulty 

 of distinguishing between C. rangiferina and C. sylvatica. A 

 general key for placing plants under their proper genera would have 

 been useful and need not have seriously increased the size of the book, 

 whose price places it within the range of the ordinary student. It 



