530 



NATURE 



[December 23, 1920 



has space for many interesting stories, which are 

 crowded out of most books, such as Mendelism, 

 "linkage" and "crossing over," artificial fer- 

 tilisation, Protozoa and disease, social insects, the 

 pedigree of the elephant, ahd the zones of life. 



Another feature is the insistence on practical 

 utility, not in any tiresomely narrow way, but 

 with a wide horizon. Zoology is for life, not life 

 for zoology. There are big ideas to be under- 

 stood, which will influence the whole conduct of 

 life. Most of these big ideas are difficult, but 

 "from a psychological and pedagogical stand- 

 point, it is surely an error to suppose that each 

 idea must be luminously clear at the moment of 

 presentation." Prof. Cockerell gives his students 

 plenty to ponder over, for he deals with the living 

 substance, the individual, "nature" and "nur- 

 ture," alcohol and heredity, variation, selection, 

 disease in relation to human evolution, eugenics, 

 and sociology from a biologist's point of view. 

 The chapters are freshly written, very objective, 

 and their brevity is as p^'chologically sound as 

 it is unusual. The author does not preach at all, 

 but he suggests the responsibility as well as the 

 happiness of playing the scientific game. He also 

 suggests the wonder of the world. So it is not 

 a common text-book this ; it is a new presenta- 

 tion. 



A third feature of great value is the introduc- 

 tion of biographical chapters. "We are too apt 

 to receive the gifts of science without asking 

 whence they came. ... As the pious studied the 

 lives of the saints, so may we pause now and then 

 to learn how scientific heroes have won new terri- 

 tory for the kingdom of science. Thus, if we 

 have anything of generous response within us, 

 we may return to our studies refreshed, resolv- 

 ing that we also, in some measure, will further 

 the good cause." So the book contains sketches 

 of Darwin, Mendel, Linnaeus, Fabre, Pasteur, and 

 others. There are numerous illustrations, many 

 of them new and interesting, others a little too 

 familiar. For the general student who is not 

 going to pursue zoology far, this is an admirable 

 text-book; for all it is a good introduction. 



The Botany of Iceland. 



The Botany of Iceland. Edited by Dr. L. Kolderup 

 Rosenvinge and Dr. Eug. Warming. Vol. ii., 

 part i. By Ernst 0strup and Olaf Galloe. 

 Pp. 248 -t- 5 plates. (Copenhagen: J. Frimodt; 

 London : John Wheldon and Co., 1920.) 



THE present instalment of the results of work 

 on the botany of Iceland is devoted to 

 the Cryptogamic flora, and contains an account 

 NO. 2669, VOL. 106] 



of the fresh-water diatoms by the late Dr. Ernst 

 Bstrup, and a description of the lichen flora and 

 lichen vegetation by Dr. Olaf Galloe. The former 

 comprises a systematic list of species based on 

 the examination of 572 samples collected by dif- 

 ferent botanists in various parts of the island. 

 The list includes a number of new species and 

 varieties which are figured in the five plates. The 

 author also gives a table indicating the general 

 distribution, and the distribution in the different 

 parts of Iceland, of the 468 forms Usted. From 

 this table it appears that 95 per cent, of the Ice- 

 landic forms also occur in the rest of Europe; 

 Asia and America come next with about 50 per 

 cent. ; comparing Iceland with the Arctic regions, 

 the greatest resemblance is with Greenland, with 

 which it has 41 per cent, in common. A classi- 

 fied list is also given of the species found in hot 

 springs from thirteen localities. 



Dr. Galloe 's account of the lichenology of the 

 island is based mainly on observations made by 

 himself during the summer of 1913, when he in- 

 vestigated fairly thoroughly several of the coast 

 districts, although he had no opportunity of exam- 

 ining the desert interior of the island. The author 

 criticises the methods of systematic lichenologists, 

 who have endeavoured to diagnose species on 

 lines similar to those followed in deaUng with 

 flowering plants. This, he maintains, has led to 

 the establishment of a large number of species, 

 many of which would probably be shown by 

 culture experiments to be forms of one and the 

 same species. Unfortunately, this experimental 

 method would be difficult and tedious, and there 

 is little hope of its being successfully carried out. 

 In the meantime it is urged that lichenologists 

 should publish extended descriptions of "one 

 single individual " of each type in order to leave 

 no doubt as to the form which it is intended to 

 describe. 



A classified list of the species is given, but the 

 greater part of the work deals with the biological 

 and ecological aspect of the lichen flora. The 

 means of propagation and of dispersal of the Ice- 

 land lichens are discussed, and an account is given 

 of the chief biological conditions in which they 

 occur. They are classified under three associa- 

 tions — the bark-lichen, the earth-lichen, and the 

 rock-lichen. The conclusion is drawn that Iceland 

 (like other Arctic countries) is poorer in species 

 according to its area than temperate and sub- 

 tropical countries, but as regards frequency- 

 number and abundance the Arctic regions and 

 Iceland are probably richer than other regions. 

 No doubt this is chiefly on account of the slight 

 competition to which the lichens are subjected. 



