Decembej»- i6, 1920] 



NATURE 



497 



servation. Many of the results are still contra- 

 dictory and far from conclusive; in fact, this is 

 a field of applied ecology demanding further study. 

 Within a given climatic zone we ought to be able 

 to associate soil types with weeds, and so prepare 

 a soil map accurate enough for working purposes 

 from surface observations of the arable land flora 

 alone, with quite a limited amount of checking by 

 analysis. 



.'\nother question to which Dr. Brenchley de- 

 votes a good deal of attention is that of the via- 

 bility of seeds as bearing on the unexpected flora 

 which often appears on the bared surface of a rail- 

 way cutting, a newly ploughed field that has been 

 long in grass, or even the spoil heap of subsoil 

 from a well or a ditch. Rank luxuriant charlock 

 almost invariably springs up, yet it is difficult to 

 see either how that somewhat heavy seed could 

 be carried there, or that it could have been dorm- 

 ant in the soil. Charlock has been observed to 

 cover a piece of newly ploughed moorland, broken 

 up for the first time in its history so far as was 

 known, and remote from any other arable land. 

 The oldest inhabitants always know that certain 

 fields will be smothered with charlock if they 

 are ploughed deep, or broken up from grass 

 after a long term of years. Yet the via- 

 bility of seeds when stored is not great, nor do 

 Dr. Kidd's experiments on the retarding effect 

 of carbon dioxide on germination quite decide the 

 question. Under ordinary conditions a seed con- 

 tinues to respire as long as it is alive; in the 

 long-stored wheats at Rothamsted, for example, 

 the embryo is burnt out, as it were. But under 

 suitable conditions — say, of the carbon dioxide con- 

 tent of the air — can the seed assume a static con- 

 dition and yet retain its germinating capacity, its 

 life, for an exceptional term of years? Dr. 

 Ikenchley's figures for the number of arable seeds 

 that germinated in samples of soil from different 

 depths taken from land which had been down in 

 grass for various periods indicate a progressive 

 dying off of the buried seed, the numbers being 

 comparatively few after thirty years of grass. 

 But the subject would repay fiirtli.r study, espe- 

 cially as regards charlock. 

 L One of the best of Dr. Urcnclilcy's chapters 



1 deals with the prevention and eradication of 



■ weeds; they may be summed up in good cultiva- 



■ tion and a sound rotation ; smother crops are only 

 H effective to keep, not to make, land clean. 

 H Chemical methods have their occasional uses, like 

 ^K spraying with copper sulphate solution for char- 

 ^1 lock, but no farmer should need them after he 

 ^K has once got his land m order. 



^B Dr. Brenchley 's book should find its place in 

 ^B* all agricultural libraries; it has the vividness and 

 ^^ NO. 2668, VOL. 106] 



interest of the record of personal observation and 

 thought that no mere compilation ever possesses. 

 A word of praise should also be given to the illus- 

 trations ; the photographs of parasitic plants 

 attached to their hosts will be of interest to many 

 botanists, while the drawings are new and. char- 

 acteristic. A. D. H. 



Facts and Theories for the Social Worker. 



(i) An Introduction to Sociology: For Social 

 Workers and General Readers. By Prof. J. J. 

 Findlay. Pp. xi-f304. (Manchester: At the 

 University Press ; London : Longmans, Green, 

 and Co., 1920.) Price 6s. net. 

 (2) The Social Worker. By C. R. Attlee. (The 

 Social Service Library.) Pp. viii-<-286. (Lon- 

 don: G. Bell and Sons, Ltd., 1920.) Price 

 6s. net. 

 (1) " 'T'HE 'unit ' in sociology is the group." 

 1 Throughout this " Introduction to 

 Sociology " the author holds fast to this basal 

 conception, and amid his many excursions into 

 varied fields of study he is constantly turning 

 back to the "group," unfolding its many 

 implications, and by its means striking a path 

 "through the jungle of social questions." 



In this treatment of the group conception 

 emerges the author's view that "the political 

 philosophers have been far too prone to present 

 an antithesis between The State and The Individ- 

 ual, whereas the conflict should always be viewed 

 as between The State and The Voluntary Group." 

 The former method gives a false superiority to 

 the State, and begs the question of the place of 

 the other groups in the life of the community. 

 But if we throw over the supreme authority of 

 the State we are left with two alternatives, neither 

 of which seems satisfactory. We may elevate 

 some other group to the highest place ; the 

 Syndicalist, for example, would make the group 

 of producers supreme. That way lies no solution, 

 for the association of producers is less representa- 

 tive than the State as it exists at present. We 

 may, on the other hand, with Mr. G. D. H. Cole, 

 attempt to balance the producers' association (The 

 National Guild) by a consumers' association; but 

 even so we are driven to look for a third group 

 with authority over both; and Mr. Cole's tertiutn 

 quid resolves itself into something not unlike our 

 present State. Prof. Findlay docs not aim at a 

 final solution of this problem. "A new region," 

 he says, " now awaits to be explored ; . . . the 

 various groups w-hich, under the aegis of the 

 democratic State, have developed self-conscious- 

 ness and power, must now be brought into har- 

 monious relation with each other and with the 



