May 5, 192 1] 



NATURE 



93 



Such bare rock surfaces, however, have also been 

 explained as due to recent subsidence or sub- 

 marine eruptions, and are not alone conclusive 

 evidence of deep-sea currents. The wide dis- 

 tribution of land material at sea by the wind is 

 illustrated by a map of thg tropical Atlantic 

 showing- the areas reached by African dust. 



The deposits next outside the continental shelf 

 are classified by Prof. Andree as the Hemipelagic 

 group, a term introduced by Krummel, of which 

 among- the most interesting are the glauconites. 

 The Eupelagic, the typical oceanic deposits, 

 include the true oozes, for which the author con- 

 veniently accepts the term Schlamm, although it 

 has been used by Walther and Penck as the equi- 

 valent of mud. It would be an advantage if 

 German authorities adopted the author's nomen- 

 clature. The account of the abyssal oozes is 

 especially full and instructive. Prof. Andree 

 discusses various attempts to estimate geo- 

 logical time by the accumulation of the deep-sea 

 deposits ; but comparison of the rapid rate indi- 

 cated, according to Murray, by the covering of 

 cables, with the extremely slow rates claimed by 

 Lohmann, justifies the author's conclusion that the 

 materials are still too scanty and contradictory to 

 yield trustworthy conclusions. 



The last sections of the book deal witTi the 

 stratigraphy of the younger marine def)osits and 

 with the quantity of radium in the sediments. An 

 account is given of the geographical distribtition 

 of the various deposits in the different oceans, 

 which is illustrated by an excellent map. The 

 final chapter on the useful materials found on the 

 sea-floor is the most scanty and least satisfying ; 

 marine placers, for example, are dismissed in a 

 short paragraph. In connection with these deposits, 

 the author remarks, regarding the much dis- 

 cussed question of the occurrence of gold in sea- 

 water, that its presence has not yet been proved ; 

 he considers that the belief in gold as a constitu- 

 ent of sea-water rests on gold introduced in the 

 reagents. This conclusion is, however, difficult to 

 reconcile with the blank results obtained by Prof. 

 Liversidge in the test analyses of pure water con- 

 ducted at the same time as those of his samples 

 of sea-waters. J. W. Gregory. 



Study of Plants in the Field. 



The Outdoor Botanist. By A. R. Horwood. 

 Pp. 284 -I- 20 plates. (London : T. Fisher Unwin, 

 Ltd., 1920.) 185. net. 



THE sub-title of this work, "A Simple Manual 

 for the Study of British Plants in the 

 Field," indicates the main purpose of the author, 

 who dedicates the book to the veteran field- 

 NO. 2688, VOL. 107] 



botanist. Dr. G. Claridge Druce. To achieve a 

 knowledge of the living plant, he says, let the 

 botanist take to the field — i.e. be an outdoor 

 botanist. As it is necessary "at the outset to 

 make collections," the first chapter is devoted to 

 methods of collecting and preserving plants, and 

 he gives many useful hints to beginners. The 

 several types of collections which may be made 

 to illustrate particular aspects of the subject are 

 also indicated. 



Following this introduction is a long chapter 

 — occupying more than a third of the volume— 

 on ecology, "the study of the homes of plants, 

 their mode of occurrence in the field, and the 

 factors of their environment." Certainly here is 

 an opportunity for the British outdoor botanist; 

 but a perusal of the pages shows that the author 

 has forgotten his original purpose, judging from 

 the frequent references to exotic vegetation — 

 e.g. mangrove swamps, desert plants in Asia and 

 Africa, palms and wind witches, and others rang- 

 ing from the Dead Sea and the Alps to the Bad- 

 lands of North America. The sources of informa- 

 tion here are too obvious for this to be the result 

 of "study in the field," but rather what the 

 author calls "armchair work"; no attempt is 

 made to relate it to British ecology. The subject- 

 matter is confused and rendered diflficult for a be- 

 ginner to appreciate by the absence of proper sub- 

 ject classification and sub-headings, and the whole 

 reads like a collection of brief statements on plant 

 habitats and communities. Misleading and con- 

 tradictory statements are frequent — e.g. on p. 84, 

 and again on p. 103, we are told that "the initial 

 stage of a large proportion of the vegetation of 

 the country is woodland." P. 91 : "A wood asso- 

 ciation on a dry soil is a damp oakwood associa- 

 tion." On p. 103 it becomes a "dry oakwood," 

 and a " damp oakwood " is the typical woodland 

 on "clay and loam." P. 74 : "There is a pressure 

 exerted by the atmosphere which increases with 

 altitude." P. 76: "In a variety of ways tempera- 

 ture affects plants. It does not vary like the 

 water supply " ; and on the same page : " In peaty 

 soils the water is inaccessible to plants, so they 

 are xerophytic." 



The author is on rather safer ground in the next 

 chapter, on "Field Botany and Survey Work," 

 and in a discursive way gives some sound advice 

 on note-taking and sketching, and on avoiding 

 work on too wide a field, advice which the author 

 himself evidently finds a difficulty in following. 

 Plans are given illustrating his " field to field " 

 work, and he explains the use of squares, grids, 

 and transects. Chapters follow on " Botany and 

 Scenery," "Phenology," and "Nature Diaries," 

 concluding with "Hints to the Teacher." There 



