December 22, 192 1] 



NATURE 



525 



disease, due to the effects of a species of Fomes 

 (F. lignostis). The life histor)' of the disease was 

 worked out, its source and the conditions of attack 

 became known through scientific investigation, 

 and then rational methods of control were de- 

 vised. 



Some optimists thought that thenceforth all 

 serious trouble was at an end, but experience has 

 confirmed the views of those who at that time 

 expressed a contrary opinion. There are now 

 known to be a number of pests, mostly fungal, 

 which threaten more or less dangerously the exist- 

 ence of the rubber trees. It is not unlikely that 

 others will appear in the future, which either have 

 not yet gained access to the plantations or perhaps 

 have not yet acquired their full virulence. At any 

 rate it may be stated confidently that the mainten- 

 ance of scientific investigation, which alone can 

 provide the essential conditions for the control of 

 disease, is a prudent measure that is of vital im- 

 portance to the existence of the whole industry. 



It is fortunate that the men who control largely 

 the development of the great rubber plantations 

 appreciate fully the services which science can 

 render, and actually has rendered in the past, and 

 this circumstance is one of the best guarantees of 

 the future success of the enterprise. 



Naturally, a considerable mass of knowledge 

 has accumulated on the causes and methods of 

 treatment of the various diseases to which the 

 rubber trees are known to be liable, and it is for- 

 tunate that Dr. Fetch, with his long experience in 

 Ceylon, should have set himself the task of pre- 

 senting, in a readily available form, the results of 

 that experience in the book under notice. By the 

 term " tree " is meant, of course, the Para rubber 

 tree, Hevea braziliensis, which from the planter's 

 point of view is the only rubber-producing plant 

 of importance. Dr. Fetch discusses the subject 

 partly from the general point of view, and shows 

 how neglect of correct principles of cultivation 

 may promote disaster. He then describes the 

 characters presented by the various parasites, and 

 their several effects on the rubber tree itself, indi- 

 cating, or at least discussing, the remedial or pre- 

 ventive measures which should be adopted. Ex- 

 cellent plates are given in the body of the work 

 illustrative of the various diseases, and we could 

 have wished it had been possible to print an 

 explanatory legend at the foot of each plate, to 

 avoid having to turn elsewhere in the text for 

 identification of the figures ; perhaps this may be 

 possible in a future edition. 



The book is much more than a mere guide to 

 the pests, animal and vegetable, that afflict Hevea. 

 Its pages abound in acute observations and sug- 

 NO. 2721, VOL. 108] 



gestions that make it valuable from the point of 

 view of general pathology, and render it of in- 

 terest to a wider circle of readers than the rubber 

 planters for whom it was primarily written. The 

 author also hints at the preparation of a companion 

 volume that shall deal with the subject from a 

 more physiological point of view. The need for 

 such a work is pressing, for quite apart from 

 the more general aspects of pathology which 

 may be expected to fall within the scope 

 of such a volume, the whole question of 

 the function of the complex latex and the 

 problems of predisposition to disease have never 

 yet received adequate treatment. For the present 

 we conclude by congratulating the author on the 

 production of a real contribution to the literature 

 of economic botany, and the publishers also de- 

 serve commendation for the excellent form in 

 which the subject-matter and the illustrations are 

 presented to the reader. J. B. F. 



Some Psychological "As Ifs." 



(i) Psychology and Mystical Experience. By 

 Frof. John Howley. Fp. xi-r275, (London: 

 Kegan Faul, Trench, Trubner and Co., Ltd. ; 

 St. Louis, Mo. : B. Herder Book Company, 

 1920.) los. 6(i. net. 



(2) The Science of Ourselves. {A Sequel to the 

 "Descent of Man.") By Sir Bampfylde Fuller. 

 (Oxford Medical Fublications.) Fp. ix + 326 + 2 

 plates. (London : Henry Frowde ; Hodder and 

 Stoughton, 192 1.) 165. net. 



(3) Religion and the New Psychology. By W, S. 

 Swisher. Fp. xv + 261. (London: George 

 Routledge and Sons, Ltd., n.d.) 105. 6d. net. 



(4) Collected Papers on the Psychology of Phan- 

 tasy. By Dr. Constance E. Long. Fp. xii + 216. 

 (London : Bailli^re, Tindall, and Cox, 1920.) 

 los. 6d. net. 



(i) T)ROF. HOWLEY'S study is a sound piece 

 Jl of work written by one who has know- 

 ledge and training along lines of thought which 

 we cannot afford lightly to dismiss. Without 

 denying the validity of the concept of sub-con- 

 sciousness (in some sense of the word) he rejects 

 that of merely automatic combination of psychic 

 elements therein. "We must," he says, "posit 

 some agency other than the psychic elements con- 

 sidered in themselves." Mystic experience is a 

 direct realisation, sine intermedio, by the agent of 

 the Agent beyond. What the author speaks of as 

 " agnostic psychology " may try to interpret this 

 in terms of illusion ; but how comes it that the 

 illusion conduces to useful and sustained effort? 

 (2) Sir Bampfylde Fuller builds a super- 



T 



