Reviews and Book Notices. 129 



Nothing quite conclusive emerges from the consideration 

 and comparison of the typical habitats instanced above, but 

 the following points may usefully be summarised : — 



1. Flowering forms are not the commonest in shade habitats. 



2. The tuber-bearing form is common in such places. 



3. The tuber-bearing form is not limited to the shade ; it 



often exists intermingled with, or close by the other in 

 even the most brilliantly lit spaces. 



4. The closed community of the grassland never harbours 



the tuber-bearer. 



5. The plant seems to retain its tuber -bearing characteristic 



even when it changes many others, on being subjected 

 to change of surroundings. 



The illumination factor does not seem to afford a solution 

 for all cases of the problem. It remains to be proved by further 

 observation and by experiments in tuber and seed propagation 

 whether or not the differences between the two types of plant 

 are inherited and are indicative of species or variety. 



: o : 



Economic Geology. By H. Ries (4th ed.). London : Chapman & Hall, 

 xviii + 856 pp., 17s. net. There is little wonder that this excellent woik, 

 with its 300 maps, sections, diagrams and photographs, and very good 

 index, has reached its fourth edition in eleven years. The author is 

 Professor of Geology at the Cornell University, and he naturally illustrates 

 the various sections of his work by American examples. Certainly that 

 continent is able to provide ample illustrations of the various ways in 

 which geological science can be employed economically. The first section 

 of the book is devoted to ' Nonmetallics,' and refers to Coal, Petroleum, 

 Building Stones, Clay, Lime, Salt, Gypsum, Fertilizers, Asbestos, Graphite, 

 Sand, Precious Stones, Underground Waters, etc. The second portion 

 refers to the various metallic ores, their occurrence, working, etc. Each 

 subject is dealt with exhaustively, and is amply illustrated by numeious 

 blocks. Though British products are not dealt with, British geologists 

 will find much of value in the volume. 



The Origin of the Earth, by T. C. Chamberlain, Chicago. University 

 Press, 271 pp. 6s. net (published in the United Kingdom by the Cambridge 

 University Press). In this book (the weight of which we are told is lib. 

 6 oz.), the author carefully reviews the various theories as to the origin of 

 our planet. He refers to Laplace's beautiful theory of the origin of the 

 solar system, that the earth was at first all gas, then became a white hot 

 mass of lava, and gradually cooled to the earth as we know it. ' But the 

 theory of a simple decline from a fiery origin to a frigid end, from a thick 

 blanket of warm air to a thin sheet of cold nitrogen, consonant with the 

 current cosmogony as it was, logical under the premises postulated, 

 pessimistically attractive in its gruesome forecast, already in possession 

 of the stage, with a good prospect of holding it — this theory of a stupendous 

 descensus none the less encountered some ugly facts as enquiry went on. 

 In seemed to accord well enough with an ice-age, if the ice age came only 

 in the later stages of the earth's history, but it was ill suited to explain 

 an ice age in the earlier geologic eras.' The author has much to say on 

 'the juvenile shaping of the earth,' due to gravitation and rotation, 

 and he gives some remarkable diagrams in support of his views. He 

 concludes that, in his opinion, what we conveniently regard as merely 

 material, is at the same time spiritual, that what we try to reduce to the 

 mechanistic, is at the same time volitional. 



1917 April 1. 



