NATURE 



281 



THURSDAY, 1)1 CEMBER 12, [918. 



LICHENS: THEIR DESCRIPTION IND 

 CLASSIFICATION. 

 I Monograph of the British Lichens. I Descrip- 

 tive Catalogue o] tin- Species in tin- Department 

 v, British Museum. By Annie Lorrain 

 Smith. I'. in 1. Second edition. Pp. xxiv + 

 520 + 7J plates. (London: Printed by Order ol 

 the Trustees of the British Museum, 1918.) 

 Price 30s. 



TI1L need for a comprehensive descriptive work 

 on British lichens has been increasingly 

 evident during the last decide. This necessity was 

 ntuated rather than satisfied when Miss 

 Annie Lorrain Smith in 1911 supplied a second 

 part to the "Monograph of British Lichens," the 

 tirst part of which had been written by the Rev. 

 James Crumble in 1X0,4. During the intervening 

 years so many .nuances had been made in our 

 knowledge of lichens, and in the method of present- 

 ing such knowledge, thai .1 revision ol the first 

 part of the monograph was absolutely essential. 

 Crombie attai bed too little importance to the repro- 

 ductive characters of the lichen, and consequently 

 his system of classification was too artificial for 

 present-day botanists. There had also been some 

 reaction against the descriptive methods of his 

 day, when lichenologistS seemed to vie with each 

 other in coining terms to express some infrequent 

 1 if a lichen-organism. 



In the second edition of part i. of the mono- 

 graph an admirable attempt has been made to 

 bring the work up to the standard of handbooks 

 on other botanical groups, to classify the lichens 

 in accordance with more modern views, to in- 

 corporate the discoveries of recent years, and 

 to simplify the descriptions of the species. 

 Another important improvement is the method of 

 illustration. The sketchy figures given in the text 

 of the first edition are replaced bv seventv-one 

 plates of drawings expressly prepared by Mr. P. 

 Highley with his usual regard for both accuracy 

 and beaut) . 



The introduction gives a short and simple 

 account of the lichen-plant. Its chief fault lies 

 in its brevity. The treatment is so excellent thai 

 an Oliver Twist attitude is engendered, and one 

 wishes that a longer accounl bad been given of 

 such matters as the relationship between the algal 

 and fungal constituents. This relationship is con- 

 sidered as symbiotic. YVallroth's and Eifving's 

 views as to the parasitic nature of the fungus are 

 not even considered worthy ol mention. The sym- 

 biotic nature of the lichen-organism is generally 

 accepted by lichenologists, and the fact that one 



symbiont (the fungus) sionally preys on the 



other (the alga) is analogous to what has b» n 

 shown by Keeble to occur in Convoluta, 



The system of classification adopted is a won- 

 derful advance on any system hitherto given in 

 British works. Both symbionts are considered, 

 the incomplete knowledge of phlogenv is requisi- 

 2563, vol. 102] 



! tioned, and less attention is paid to the vegetative 

 1 b.'iraiters of the thallus. 



The arrangement of the spores on basidia or in 

 asi i give the two sub-classes Basidiomycetes and 

 ( Ascomycetes. Since all British lichens belong to 

 the latter sub-class, it is tin- only one considered, 

 and is divided into two series, Gymnocarpeae 

 with open apothecia, and Pyrenocarpeae with 

 perithecia. The Gymnocarpeae are subdivided into 

 three sub-series: (1) Coniocarpineaj with powdery 

 apothecia or perithecia; (2) Cyclocarpinere, having 

 apothecia with open discs and fungal ancestors 

 belonging to the Discomycetes ; and (3) Graphi- 

 dinea?, having apothecia with narrow discs, their 

 fungal ancestors being allied to the Hysteriaceae. 

 The sub-series Cyclocarpineas, with which part i. 

 is mainly concerned, is next split up into orders 

 according to the algal symbiont, the presence or 

 absence of a thalline margin to the apothecium, 

 and the form of the thallus, the relative import- 

 ance assigned to these characters being generally 

 in this sequence. 



It is .unfortunate that the name of order is 

 retained for groups which, in accordance with 

 modern views, ought rather to be called families. 

 The retention of order cannot be altogether justi- 

 fied by the fact that this name was used for similar 

 groups in part ii. 



Some of the families have somewhat incongru- 

 ous components if the views of sporologists have 

 sufficient importance attached to them. Phvsei- 

 aceae (unintentionally given as Physiaceas on 

 p. 1 So,) includes Xanthoria and Placodium with 

 colourless polarilocular spores, as well as Physcia 

 with dark spores which are more 1 -septate than 

 polarilocular. Xanthoria and its allies would have 

 been better placed as a separate family. Lecano- 

 racea' includes Lecanora, having eight simple 

 spores in the ascus, Acarospora with manv simple 

 spores in the ascus, and Lecania and other genera 

 with septate spores. 



Owing to the different system of classification 

 a long appendix is necessary to bring the work 

 into conformity with part ii. In this appendix the 

 species of Cladoniaceae and Gyrophoracea? are 

 described, the members of the Sarcogyne section 

 of Lecanora are rightly placed as Biatorellas, 

 whilst Dirina, Roccellae, Pyrenidium, and a 

 number of species new to the British Isles are 

 described under their proper families. 



There is a considerable amount of alteration of 

 names, mostly well-warranted according to the 

 rules of priority. It is unfortunate that some 

 well-established names suffer, and one could wish 

 that the author had followed a similar course as 

 that adopted for Lecanora campestris, the gene- 

 r.d)_\ accepted specific name being retained, whilsl 

 the doubtful, though prior, name of punctatus was 

 rejected. Other authors have considered them- 

 selves justified in rejecting some of the combina- 

 tions used by Miss Smith, on account of their 

 inappropriate or doubtful nature. Synechoblasins 

 rupestris displaces Collema flaccidum, though 

 many authors have considered the specific name 

 of rupestre as of too doubtful priority to take the 



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