Vol. X. No. 24.3. 



THE AGRICULTURAL NEWS. 



295 



THE PHYSIOLOGY AXD DISEASES OF HEVEA 

 BRASILIENSIS, by T. Fetch,. B.Sc, B.A., Mycologist to 

 the Government of Ceylon. London, Didan and Co., Ltd., 

 7s. 6d net. . 



This book must be regarded as a most valuable addition 

 to the literature dealing with the Para rubber tree (Hevea 

 Irasiliensis). It is evident from the simijle though scientiti- 

 calh" accurate method in which the subject matter is treated 

 that it is primarily intended for the planter, but the careful 

 descriptions of the diseases, accompanied as they are through- 

 out by the scientific diagnoses of the fungi causing them, are 

 of no less value to the plant pathologist. The sections 

 treating of the fundamental facts of plant anatomy and 

 physiology which underly all systems of tajjping, and that part 

 dealing with the effect of different systems on the tree may 

 well receive the careful attention of all owners of estates, 

 whether private individuals or directors of companies. 

 Finally, the careful critical method followed by the author 

 in considering all tbe experiments which he quotes to 

 illustrate his points, as well as the principles contained in 

 the chapter entitled The Art of Experiment, should serve as 

 a guide to all engaged in the conduct of agricultural 

 research experiments in the tropics. 



The style of the book is simple, lucid and definite; the treat- 

 ment of the subject matter is excellent. There is a marked 

 freedom from any casual or inaccurate employment of scien- 

 tific terms, while a clear-sighted and critical attitude is main- 

 tained throughout, which leads to the rejection and overthrow 

 of many prevalent but inaccurate beliefs, having no sound 

 basis in scientific observation, often contrary to all known 

 botanical facts and, generally, belonging to the category of 

 popular natural history. Such beliefs are not merely pas.sed 

 over summarily, the reasons for their dismissal are given, and 

 this treatment of them serves as a good model of the way in 

 which pulilished scientific statements should be criticized by 

 the reader: a further illustration of this is provided by the 

 author's discussion of the experiments considered in the text. 



The book is really constructed in two parts. The first 

 deals with the general structure and physiology of the plant 

 and outlines their significance in the consideration of prob- 

 lems relating to tapping and to the general health of the tree. 

 This matter is contained in seven chapters whose titles are as 

 follows : I, The Structure of Hevea; II, Latex and Rul.>ber; 

 III, The Strength of Plantation Rubber; IV, Physiological 

 Considerations; V, Tapping Systems and their Etfect on the 

 the Tree; YI, Tapping Experiments and Their Teachings; 

 VII, The Art of Experiment. 



The subject matter in these chapters is interesting 

 throughout. The description given in Chapter I, though clear 

 and easily understood, might perhaps have been illustrated by 

 a few simple diagrams. The phenomenon, usually known as 

 'wound response', is frecjuently attributed tn a vital stimulus of 

 irritation produced by wounding. The author, however, after 

 drawing attention to the lower percentage of rubber contained 

 in the latex obtained at such consecutive tapping?, puts 



forward another view. According to this, the phenomenon 

 is due to the combined effects of gravity and the infiltration 

 of water into the latex tubes. The removal of the latex on 

 the first day permits of the infiltration of water into the tubes. 

 This water lessens the viscosity of the latex, and the flow ob- 

 tained on the second day is consequently greater, while the 

 percentage of rubber obtained from it is lowered. Thus the 

 phenomenon is controlled by the factors to which the increased 

 flow of latex in wet weather must also be attributed. 



Many other practical points of interest are discussed in this 

 portion of the book, such as the amount of damage inflicted 

 upon trees by various tapping systems, the eflects of difterent 

 instruments for tapping on the nature of the renewed bark, 

 and many others, but, unfortunately, space does not permit 

 of their consideration here. 



The second half of the book deals with specific diseases 

 and malformations. It is divided as follows: General 

 Sanitation, Leaf Diseases, Root Disea.ses, Stem Diseases, 

 Abnormalities in Hevea, Prepared Rubber, Other Fungi on 

 Hevea 



In considering the question of protective belts, under 

 the heading General Sanitation, the author points out the 

 difticulty of obtainmg any suitable crop for their formation, 

 and thinks that, in consequence, they must consist of useless 

 forest trees. But it seems that certain useful timber trees 

 might be employed for the purpose, especially in districts 

 with good means of communication. The final conclusion 

 reached does, however, seem true, namely, that the employ- 

 ment of such belts of forest is only practicable when a district 

 is being opened up, and that protective belts are out of the 

 question in most countries. Several other important points 

 receive attention in this chapter, such as the Removal of 

 Stumps, Pruning, Planting Distances and Cover Crops. 

 Finally, the evidence on the matter of the internal applica- 

 tion of fungicides is summarir.ed, and the conclusion is 

 reached that at present such treatment cannot be recom- 

 mended. 



The leaf diseases mentioned are none of them considered 

 to be of any great importance, and only the principal ones are 

 given in Chapter IX; the other fungi found on the leaves of 

 this plant are recorded in Chapter XIV. The root diseases 

 are three in number. The first is due to Fomes semitoslus. Berk.; 

 this is a well known disease, but the author points out that 

 the name of the fungus should probably be Fomes AuOerianus. 

 The second is the brown root disease due to Hymenochaete 

 nojia. Berk , and the third is caused by Sphaerostilhe repens, 

 B. and Br. All of them commence their attacks, in the 

 majority of instances, from decaying jungle stumps. 



The stem diseases are canker, due to Pliylophthora ' 

 Fiiheri, Maubl., which al.so causes canker of cacao; pink 

 disease due to Corticiunis salmonicolor, B. and Br., formerly 

 known as Corticiinn javanicum, Zimm.; die-back, due to the 

 combined action of Gloeospovium. alboruhriim. Fetch, and 

 Bot ryodlplodia theohromae, Pat., which latter is the same as 

 Thyridaria tarda, Bancroft (see Agricultural News, Vol. X 

 p. 286); a disease due to Fusicladium sp. in .Java; a disease 

 of stumps due to Botryodiplodia theohromae; a new stem 

 canker not previously described, caused by Coniothyrium sp.; 

 and a stem disease of seedlings due to Pestalozzia jMilmarum, 

 Cooke. 



The whole of this section is very thorough and brings 

 the information covering the diseases up to date, with the 

 exception of the work very recently published by Bancroft 

 and referred to above. All that is necessary to complete the 

 literature dealing with the pathology of Hevea hra.tiliensis 

 is a similar work treating of its insect pests. 



