W. B. CROW. Lichens. By ANNIE LORRAIN REVIEW I 02

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1 I 02 W. B. CROW (9) GARDNER, N. L. Cytological Studies in Cyanophycez. Uniu. of California Publications, Bot (10) GoMoNT, M. Recherches sur les enveloppes cellulaires des Nostocackes filamenteuses. Bull. SOC. bot. de France, SBr. 2, T I111 KIRCHNER. 0. SchizoDhVceae in Enrrler u. Prantl. Die naturl. Pflunzenfam \ I - Teil I, Abt. I u.* 1i98. (12) KOHL, F. G. Uber die Ovganisation und Physiologie der Cyanophyceenzelle, u. s. w. Jena, (13) LEMAIRE, A. Recherches microchimiques sur la gaine de quelques schizophycbes. Journ. de Bot. IS (14) LEMMERMANN, E. Algen in Kryptogamenflora der Mark Bralcdenburg, (15) OLIVE, E. W. Mitotic division of the nuclei of the Cyanophycez. Beihefte Bot. Centralbl (16) TILDEN, J. Minnesota Algae. Vol. Myxophycee Minnesota (17) VIRIEUX, J. Sur les gaines et les mucilages des Algues d eau douce. Comptes rendus Acad. des Sc (18) WEST, G. S. Algu?. Vol. I. Camb. Bot. Handbooks. Cambridge, (19) ZIMMERMANN, A. Botanical 7 Microtechnique, trans. J. E. Humphrey. New York, REVIEW Lichens. By ANNIE LORRAIN SMITH, F.L.S. Pp. xxviii and 464, with 135 figures in the text. (Cambridge Botanical Handbooks.) University Press, Price 55s. The publication of this second vo1u me of the Cambridge Botanical Handbooks has been delayed owing to war conditions, and if this delay is, in any way, responsible for its excellence, all students of lichenology must congratulate themselves that it has occurred. It is so full of matter that one marvels at the wonderful application of the author in collecting and arranging the work on the various aspects of lichenology into critical articles, and then weaving these articles together so as to form a connected whole, which may be read with plesure and profit, not only by a lichenologist, but also by a general botanical reader. The Bibliography of works consulted in the preparation of the volume is an extensive one, and includes all the important books and papers on lichens. Very few British articles on lichenology, whether important or otherwise, are omitted. One cannot remember a dozen which are not included, and such omissions as there are involve no great sacrifice to the completeness of the work. Even Wheldon s article on mites using the pits of immersed apothecia for their homes is included, though such a paper, interesting as it is, seems rather out of place in a general work on lichens. The terminology is much simplified as compared with that employed by Leighton and Crombie, and the author must be congratulated on the ability with which she has lucidly explained the morphology of lichens without requiring an extensive glossary. A glossary is given, but many of the terms in it are sparingly, if at all, used by the author. The value of Crombie s monograph was largely discounted by the technical jargon he used.

2 Reviao 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 duration, 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 wreathmaking, and this is not mentioned. Usneas are the chief lichens used, but Ramalinas and Evernia prunastri are also employed. Cbdonia rangzferina is referred to on p. 401 as the favourite food of the reindeer. 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 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 experiments 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 hyphz 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 liehenologist 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 Trentepohlia, 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 Tolypothrix, but more often it is still less like Scytonema. The algal cells in

3 104 ReUlt?W Polychidium muscicolum and Leptogium microscopicurn seem very similar, though those of the former are given as Scytonema, and those of the latter as Nostoc. Figures of the algal symbionts are given from the free alga?. It would have been better if illustrations of the actual gonidia had also been given, since a young lichenologist may be led to expect to find algal symbionts in the lichen like those figured. Many instances of what various workers have called saprophytism and parasitism are mentioned. Some of the so-called saprophytes amongst lichens are no more entitled to the name than are radishes from a well-manured garden plot, and some of the examples of parasitism are scarcely more so than when plantain smothers other plants and feeds on the derived humus; others, in which digestive action precedes the actual covering of the host, are better examples. Malme s view (quoted on p. 261) that Buellia verruculosa and B. athalea may be living on the thallus of Rhizocarpon distinctum with which they are constantly associated, is not supported by the distribution of these lichens in the British Isles. When Miss Smith expresses her own views on these SOcalled parasitic and saprophytic lichens, they are generally of a sceptical or qualifying nature, though it is not always easy to perceive how far she agrees with the work and views she gives an account of. The colour of lichens has an excellent section devoted to it, and the effect of light on this colour is referred to in another section of the chapter dealing with physiology. The darkening or deepening of the colour is attributed to the influence of light. In some lichens it may not be the only factor, the lack of water and nutriment may also contribute to the darkening. The dark colour of such plants as Rhizocarpon confervoides, Buellia impressula, and Lecidea latypea on shingle, is due to the predominance of the hypothallus, the nutrition being deficient for the proper formation of the thallus. The change in the colour of the apothecia (p. 245) is of frequent occurrence, and sometimes is well marked where a number of stones have lain heaped together for many years. The apothecia on the illuminated portion may be very dark whilst those which are shaded are pale in colour. The darkening of old apothecia, e.g. Candelariella vitellina, may be due to decomposition products. Those who uphold Church in his views of a direct evolution of lichens from algre, may derive some consolation from the following passages, when isolated from their contexts. In Verrucaria mucosa...and in some other sea-washed species the arrangement of the tissue elements recalls that of crustaceous Florideae such as Hildenbrandtia, Cruoria, etc. (p. 73). Mechanical tissue scarcely appears among fungi (p. 105)- These attaching sheaths (of Usnea, etc.),..may be more truly compared with the primary thallus of the red algae, Dumontia and Phyllophora, which are similarly affixed to the substratum (p. 111). Such a view might be possible if we could regard lichens and Florideae as derived from some common ancestor (p. 179). The hyphae travel in the sheath alongside the cell-rows and the symbiotic plant retains the tufted form of the alga as in Lichina with Rivularia, Leptogidium with Scytonema, and Ephebe with Stigonema (p. 284). In the phylogenetic chapter, and more definitely in an appendix, Miss Smith opposes these views, and in so doing voices the opinions of lichenologists in general. Even those who have seen the shaggy covering of Lichen on the cliffs facing the Atlantic ( The Lichen as Transmigrant, J. of Bot. 1921, p. 45) find little evidence in support of Church s views and much in conflict with them. A large amount of space is given to Zahlbruckner s method of classification. The appreciation given to it is well deserved, as it is the most natural and thorough grouping of the lichens which has been attempted. Miss Smith s lucid description brings it within the range of every British student. Some desirable information has been omitted, probably owing

4 to considerations of space. One would have liked to know what British species are referable to the genera Polyblastropsis, Blastodesmia, Phaeographina and Pilocarpon, the position of Bilimbia, why Acrocordia is merged in Arthopyrenia; in fact, a more detailed account of Miss Smith s personal views would have been very acceptable. Her caution in regard to some parts of Zahlbruckner s classification can easily be understood; still, the grouping of the lichens with many-spored asci in Acarosporacea: seems justifiable, and the separation of Xanthoria from the Physcia group is supported by the differences in the septation and colour of the spores, of which the importance in classification has scarcely been sufficiently appreciated by our older British lichenologists except Mudd. With regard to Zahlbrnckner s lumping together of a number of genera into Lecideacea: and Lecanoracea: one may be heterodox and less in agreement. Too much importance may be assigned to the systematic value of I the distinction between lecideine and lecanorine apothecia, insisted upon on p Lecanoracea may bepolyphyletic from lecideoid ancestors and an extension of the principle which includes Blastenia with Placodium and Buellia with Rinodina seems justifiable. Candelaria and Candelariella, despite the absence of parietin, appear to have more affinity with Xanthoria and Placodium than with the groups under which they are placed. In a few instances one is not prepared to accept Miss Smith s conclusions, as for example, in the general summing-up of the evidence given in the case of pycnidia versus spermogonia, where the former is favoured. The evidence, however, on both sides is given impartially and the reader may use his own judgment. The evidence of Stahl, Darbishire, and others, as to contact between the spermatium and trichogyne, is not challenged. The author s chief point against the spermatium being a gamete rests on its power of germination. The possibility of a gamete settling down to produce a new plant is familiar to algologists, and there does not appear to be any inherent improbability in the reappearance of such an ancestral character, when the spermatium is cultivated. The differences between the colourless, polarilocular spores of Xanthoria, and the brown, one-septate spores of Physcia, appear greater than is suggested on p According to the text, the median septum arises as. an ingrowth from the sides of the cell. In Xanthoria the ingrowths do not completely meet, so that a canal is left between the two polar chambers. In Physcia the ingrowths meet and two distinct chambers are formed. The illustrations (Fig. 107) show a median septum crossing not only the central canal, but also traversing the ingrowth from the sides of the cells, so that the median septum of Physcia traverses what is considered to correspond to a median septum in Xanthoria. The Xanthoria family with Teloschistes, Xanthoria, Placodium, Callopisma and Blastenza, seems to be a distinct family from that of Physcia with the more or less corresponding genera of Anaptychia, Physcia, DimeEmna, Rinodina and Buellia. The references to similar cell-division in Alga: would have been better if Spha:roplea had been mentioned instead of Cladophora; in the latter the wall is completed, whereas in Sphaeroplea, an open central pore is sometimes left. In some Siphonales (e.g. Callipsygma) an open pore is left; in Codium the stopper is incomplete when young and complete at an older stage. There are few inaccuracies or inconsistencies in the text, and for some of these the author is not responsible, as she is quoting the views or work of others. Some accident causes Collema nigrescens to have a distinct cellular cortex on p According to p. 3 7 lichens ~ alone are able to live on bare rock, whilst it is stated on p. 394 that in tropical countries the first vegetation to settle on bare rocks would seem to be blue-green gelatinous alga. On p. 374 Collemopsidium is said to be

5 I06 R&t?W the only Xanthocapsa associate that is silicicolous and on the opposite page Psorotichia lugubris is listed. The statement on p. 250 that rust lichens grow on rocks that are frequently under water needs qualifying, as only one of the four examples given grows in such situations, and other exceptions could be mentioned. The formula of such a highly comlex substance as triethylprotocetraric acid may still be given as ~nah,,o~, even though it is an empirical one (p. 221). The yellowcoloured medulla of Parmelia subaurifera (p. 226) is usually white in southern plants. In the rdsumd of the work done on the shingle lichens at Blakeney Point, Lecanora badia is given as abundant. During some observations on the shingle beds in 1921, L. badia was not seen, though Lecania prosechoides was abundant and is probably the lichen meant. Placodium lobulatum was also abundant on the low shingle and is probably the lichen referred to as Lecanora citrina var. incrustam. Some biologists may reasonably object to the use of copulation for contact or fertilisation (p. 160, etc.), rhizoid for rhizina (pp. 92 and 93) and prothallus for hypothahs or protothallus (p. 187), as their use may cause confusion, or are scarcely in accordance with their use in other branches of biology. The physiological meaning of the statement quoted on p about waste products and products of deassimilation is rather obscure. Bitter s suggestion of hybridity between Parmelia physodes and P. tribulosa, owing to the intermingling of their soredia (p. 146), would be more convincing if the specific segregation of these two plants was established. The phylogeny of the Coniocarpineae (p. 276) may be more easily explained by assuming that their fungal ancestors belong to an extinct group. The general get-up of the book is excellent; headings, spacing, wide margins and illustrations give an artistic setting which such a great work deserves, but (and there is a very objectionable but) the price is much too high. The work ought to be readily accessible to every student of plant-life, and the high price will prevent such a desirable consummation. Perhaps it would have been advisable to place some of the more critical matter in smaller type, if such a course would have resulted in a cheaper book. Much of the matter dealing with the chemical contents of the cell could have been so treated. A general consideration of the book makes one realise what a great diversity of opinion exists on very many lichenological questions. Even in regard to the distribution of lichens in the Polar regions, Darbishire and Hue are at variance. According to the former 50 per cent. of Antarctic lichens are also Arctic, whilst Hue states that 81 per cent. of Antarctic lichens are special to this southern region. The magnitude of the task in considering and coordinating such a variety of views so as to form a connected story may well have appalled a stout heart, and we may be proud of the fact that it has been so splendidly accomplished by one of our own botanists. W. WATSON.