Vol. V. No. 99. 



THE AGRECULTUEAL NEWS. 



43 



BORDEAUX MIXTURE. 



The following review of a paper in the Landiv- 

 irts chaft licJies Jahrhuch by R. Schandler on recent 

 work relating to Bordeaux mixture is extracted from 

 the Botanical Gazette, for December 1905 : — 



In the large literature on Bordeaux mixture, secondary 

 plisiological effects on plants, not due to the fungicidal action 

 of the nii.xture, have frequently been described. These 

 effects are of two kinds : first, a stimulating effect resulting 

 in darker green, thicker foliage, with increased starch 

 production and decreased transpiration ; second, direct toxic 

 action on the foliage and fruits. The whole question, on 

 which many conflicting views have been published, has been 

 critically examined by Schandler. JIany writers have 

 attributed the stimulating action of Bordeaux mixture to the 

 entrance of small quantities of copper into the plant, both 

 through the cuticle and the stomata. Schandler finds that 

 leaves injected with a solution of coi^ier sulphate, 1 part in 

 10,000,000, and allowed to lie in the solution twenty-four 

 hours, showed poisonous effects, while much more concen- 

 trated solutions were unable to penetrate the uninjured 

 epidermis when applied externally. The argument is that 

 the cuticle prevents the penetration of very dilute solutions 

 of copper, such as might result from solution of the 

 particles of copper compounds applied to the leaf, but if any 

 copper enters the cells, the results are injurious, never 

 .stimulating. By growing plants in water cultures with 

 dilute solutions of copper, it was found that the young roots 

 were gradually killed, whereupon another crop of roots was 

 formed, which also was finally killed, etc. Here again, there 

 was no stimulating action, although the top of the plant 

 remained uninjured, showing that the copper was accumulated 

 by the root cells, even from very dilute solutions, but was 

 not passed on into the vascular system. In ."oils, a more 

 concentrated solution of copper was required to produce toxic 

 ■effects on account of their absorption. By appropriate 

 experiments, it is also shown that neither the lime compounds 

 nor the traces of iron produce stimulating effects. 



The true explanation of the phenomena is found in the 

 physical action of the coating itself. The same results were 

 ]iroduced by shading plants with glass to which a spray of 

 Bordeaux mixture had been applied, also by the use of thin 

 paper or dust. Good results were obtained only in bright, 

 sunny weather, while injury resulted during cold, rainy 

 seasons. This, no doubt, explains the contticting reports of 

 various investigators. The toxic effect of the mixture is 

 found to be due to solution of the copper, caused by the 

 secretions of glandular hairs, as in the peach, pha.seolus, and 

 sunflower. 



Rubber planting in Jamaica. His Excellency 

 the Governor, at a meeting of the Jamaica Agricultural 

 Society a short time ago, introduced the subject of rubber, 

 and commended it to the attention of planters. Members 

 present declared themselves willing to undertake the cultiva- 

 tion, and the Director of Public Gardens and Plantations 

 was in.structed to procure seed. About 6,500 Para rubber 

 plants (out of 10,000 seeds of Para from Singapore), and 

 4,500 Castilloa plants have now been raised. They have all 

 been bespoken, but applications will be booked by the 

 Director, and a further supply of seed, both of Para and 

 Castilloa, will be obtained next year. Applications should 

 be sent in at once, as the demand for seed is very great, and 

 soon there will be none available, even at a year'.s notice. 

 (Bulletin of (he Department of Affriculture, December 1905.) 



SHADE-GROWN TOBACCO AT ST. KITT'S. 



The following extract is taken from a letter from 

 the Agricultural Superintendent at St. Kitt's to the 

 Imperial Commissioner of Agriculture on the subject 

 of an experiment with shade-grown tobacco in that 

 island. This is in continuation of the note that 

 appeared in the last number of the Agricv.ltural News 

 (Vol. V, p. 26) :— 



I forward bj' this mail a few photographs of the 

 tobacco grown at La Guerite under shade of cheese cloth, 

 which well illustrate the height of the tobacco, and the size 

 of the leaves. 



The tent was erected over \ acre of land at La Guerite 

 in the beginning of October, and the plants were put out on 

 October 18. In two months, the untopped plants were 7 feet 

 tall and the topped plants 5 feet. The reaping of the 

 tobacco was commenced on December 23. Half of it is 

 being cured on the stalk, and half is being primed. The 

 experiment, so far, has been satisfactory, and every effort is 

 being made to ensure success in the curino- and fermentation. 



GALLS ON TREES. 



Interesting specimens of a gall on the bread and cheese 

 tree {Pitheeolobium Unf/uis-cati, Benth.) were exhibited 

 by Mr. John Hutson, M.B., at the last meeting of the 

 Barbados Natural History Society. Other specimens of 

 galls have been forwarded to the Head Office of the 

 Imperial Department of Agriculture by Mr. E. D. 

 Anstead, B.A., Agricultural Superintendent at Grenada. 

 These occur on cacao and sometimes assume peculiar shapes. 



Our knowledge of the primary cause of gall formation 

 is very small. It \\'Ould appear that only embryonic or very 

 young cellular tissue reacts, and the galls found on leaves 

 and branches are generally of old standing. Galls are either 

 caused by parasitic fungi or by insects. 



Those caused by fungi generally appear as abnormal 

 enlargements on the plants attacked. The fungi live on 

 the contents of the host cell, but give it time to react to the 

 stimulus exerted by the intruder. 



Those caused by insects start with the laying of the 

 egg in the embryonic tissue of the leaf and stem. The 

 resulting larva begins to feed on the cells, and therefore 

 irritates the surrounding tissue. Rapid growth and cell 

 division follow in the plant. This is of great advantage 

 to the young larva as more food material is brought up for 

 use. 



Concerning the development of this excessive localized 

 growth considerable controversy has arisen. Formerly it was 

 thought that the growth was due to some poisonous irritating 

 fluid injected by the parent insect at the time of the laying 

 of the egg. Eecent research has shown that this is not 

 the case, for attempts to produce galls artificially by 

 injections of various poisons, etc., have failed, and therefore 

 the stimulus for the tissue formation is now taken to 

 be similar to that exerted in the healing of an ordinary 

 wound. If this be so, how then 

 produced by fungi be accounted for^ 



Many of the galls have definite shapes, which depend 

 on mutual reactions between the species of plant on the one 

 hand, and the species of gall insect on the other. A typical 

 gall shows three distinct layers of tissue, surrounding the 

 chamber in which the larva of the insect lies: (1) an outer 

 layer of thin-walled cells, covered by the epidermis ; (2) 

 a layer of thick-walled cells, which forms a protective layer 

 to the insect, and (3) an inner layer of thin-walled cells, filled 

 with food material on which the insect lives. 



can the enlargements 



