NATURE 



401 



THURSDAY, J \\1 WUN 23, 1919. 



DISEASES OF PLANTS. 



Fungi and Disease in Plants: An Introduction /<< 



the Diseases of Field and Plantation Craps, 



ally those of India ami the East. By 



E. J. Butler. Pp. vi+547. (Calcutta and 



Simla : Thacker, Spink, and Co., 1 <jiS. ) 



Tl I E research work published from time t<> 

 time bv the stall oi the Agricultural Re- 

 search Institute at Pusa lias shown a high 

 standard, which is well maintained by this pioneer 

 volume on the fungous diseases oi field and 

 plantation crops of India and the East, 

 written by Mr. E. J. Butler, Imperial mycologist 

 for India. When we realise what a dull book 

 might have been compiled in the old "museum 

 catalogue " manner, we gratefully extend a warm 

 welcome to this volume, through which the spirit 

 of research breathes so strongly. 



The hook is divided into two sections, and in 

 each the numerous references made to the work 

 of mycologists all the world over, and the excel- 

 lent bibliography, are evidence <>l the wide read- 

 ing of the author. 



In part i. we have a clear!) written intro- 

 duction to the study of mycology, with 

 chapters on the nature of fungi, their food, 

 the life-histories ol parasite's, the Causation of 

 disease, and the principles of the control of plant 



diseases. 



We have so lew scientific clat.i as to "condi- 

 tions affecting the host" and "predisposition" 

 that a satisfactory treatment oi the subject is 



almost impossible. Mr. Butler states (p. 124) that 



"the mere groNvth of a plant under glass may 



e its resistance" to rust and mildew; just 



recently the converse has been proved to be tin 



ase with respect to the hop-plant and its mildew. 



\nyone who has studied the attacks of the oak- 

 mildew in woods in England will find it impos- 

 sible to believe the statemenl (p. 1 i * >> that "the 

 injurious effect of factory smoke " is required to 

 "lower the resistance" of this host-plant. Mr. 

 Butler assumes that the new varieties of potatoes 

 put on the market as "blight resisters " are all 

 realh so at the start, and that they "deteriorate " 

 and become susceptible. It may lie asked whether 

 there was really scientific evideni e of such original 

 immunity, or whether it is not a common "trick 

 of tin- trade " to describe new varieties as "blight 



resisters." \\'c still remember the shock of find- 

 ing Septoria petroselini and Cercospora melanis 

 virulent 1\ infesting a new variety respectively 

 and cui umbi 1 , each described as " 's 

 Disease Resister" ! That immunity does not 

 "it," si. to speak, appears to be proved 

 with regard to certain varieties ol potatoes which 

 resist the attacks of "wart-disease" irrespective 

 • •I the age of the variety or the vigour of the 

 shoot. Again, in those cases where it appears that 

 a parasitic Fungus recently introduced into n 

 country diminishes its virulence of attack, the 

 possible explanation must not be lost sight of that 

 XO. 2569, VOL. I02] 



as with the chrysanthemum when its rust found 

 its way into this country — the most susceptible 

 varieties go out of cultivation and are replace" 

 b\ more resistant ones. 



Part ii. comprises "Special Diseases." Nearly 

 JOO diseases of Indian crops are mentioned; each 

 disease is given, first, a general description, 

 admirably written for the needs of the "man on 

 the hind." The description of each growing 

 crop and its particular disease has that invigo- 

 rating freshness which the use of the field-notes of 

 a keenly interested investigator alone can give. 

 No planter could wish for better accounts of the 

 "Tikka" disease of the ground-nut, of the seed- 

 ling blight " of castor, and of the "red rot " and 

 "wilt" of the sugar-cane; the author's strong, 

 dear, descriptive style is also well shown in his 

 treatment of the diseases of tea and rubber. After 

 the general description of the disease, tech- 

 nical details are given sufficient to satisfy 

 the needs of the student. The very numerous 

 illustrations, many of which are from drawings 

 of native Indian artists, or copies by them in ink 

 or wash of Mr. Butler's fine pencil work, are 

 exceptionally good : the sensitive drawings of 

 leaves — e.g. in Figs. 124 and 127 — are a delight 

 artistically. 



Many columns here could be rilled with extracts 

 from this book of great interest both from the 

 economic and the purely scientific sides. We are 

 enabled to realise the special difficulties of com- 

 bating fungous diseases in such countries as 

 India; to see "the spraying coolies who have to 

 climb the trees"; to watch the distribution 

 through the villages of Bombay of "one-anna 

 packets of copper sulphate" (sufficient to protect 

 against "smut" enough seed of "jowar" to sow- 

 four aires); and to admire the industry of those 

 tea-planters who, over an area of 1300 acres, 

 hand-picked and destroved in two seasons more 

 than 32 tons of leaves affected with "blister 

 blight" (Exobasidium). The money losses in- 

 volved in many of the diseases is very consider- 

 able; the value of the grain of "jowar " destroyed 

 bv "smut " in Bombay alone is estimated to ex- 

 ceed a million sterling annually. Among a mass 

 of interesting facts we may note the correlation 

 of epidemics of wheat rust with the varying 

 humidity of the air; the killing of the mycelium of 

 Phytophthora infestans in the potato-tuber by the 

 climatic heat of the plains; the marked parasitism 

 of Cladosporium (which appears to be becoming a 

 pest in England) on wheat and "jowar"; and 

 the existence of specialised " flax " and "linseed 

 races of MelampSOra lini. It may be pointed out 

 that the general statement (p. 62) that "in black 

 1 ust the aecidial form on the barberry has 

 the same specialisation as the uredo-teleuto," 

 while true as regards some countries, needs to be 

 qualified by reference to the work of Arthur in 

 igio, which showed that in the United Stales the 

 specialisation of parasitism has proceeded on dil- 

 ferent lines; the genus Oospora (p. Si) is now re- 

 placed b) Actinomyces; the word "botanical" is 

 used wrongly (pp. 60, 61) to mean "mprpho- 



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