Vol. VIII. No. 194. 



THE AGRICULTURAL NEWS. 



30» 



(C. pii'jeiiccns). The fruits of the first are always gathered 

 when small, and in this state are crisp and of excellent 

 flavour. Those of the snake cucumber are cylindrical, 

 twisted, about 20 inches long, light green yith dark blotches, 

 and covered with soft, woolly hairs. T^6la;jt has cylindrical, 

 generally straight fruits, vhich are "about 10 inches long. 

 The skin is white, or in various shades of green, and mottled; 

 it is covered with short hairs and shows depressed lines. All 

 these are eaten as salads. Of the vegefealDle marrows, there 

 are five chief kinds, three of which belong to Gurai-hitu Pt/'o, 

 and two to C. vtoxrhdfn The larger pumpkins (C. laaxiimt) 

 are grown to a very small extent in Egypt. 



As has been stated, the article also mentions the 

 domestic sponge and the calaba.sh gourd. These are, of 

 course, well known in the Wes£' Indies, though the 

 spotige in Egypt is provided from Lujf'a ac(jyptiacit. 

 and not from L. (icutainjala, as is the case here. It 

 will be remembered that the calabash gourd (Lngeii- 

 arld rulgaris) is used for the bowls of the now-famed 

 calabash pipes. This is found native in the West Indie.s, 

 and seeds of the plant have been obtained from South 

 Africa by the Department and distributed among 

 several of the Botanic Stations. (See A(jricu,lta ml 

 -Xeivs, Vols. V, p. 399 : VI, pp. 12:^, 298 and 41.5 : VII, 

 J). 124:VIII, p. 21.) 



THE ECONOMIC IMPORTANCE OF THE 

 MANGROVE. 



This subject is dealt with, from the point of view 

 of the exploitation of the mangrove in the Philippine 

 Islands, in the PJi'dipiiirie Jownuil of Science for May, 

 1909. The following e.Ntracts from the article should 

 be of interest : — 



In tha United States, and in other countries where large 

 amounts of leather are manufactured, the forests yielding 

 native tanning materials have been so far exhausted that 

 these nations must look to other countries for their source of 

 supply. At the present time very large quantities of tan 

 barks and cutch are imported into the United States from 

 liorneo. Dutch East .\frica, Brazil and other tropical 

 countries, and the use of mangrove tanning materials is con- 

 stantly increasing. The most abundmt source of tanning 

 substances in the Philippines is th; mangrove swamps of the 

 Islands. At the present time there is no mangrove bark ex- 

 ported from the Philippines, and as yet the area of these 

 ."wanips is not known. They occur as narrow fringes along 

 the coast, or in considerable areas at the months of large 

 rivers, especially at the head of bays. Some limited areas 

 have been mapped and measured by the Forestry P)Ureau. 



There are three large cutch factories in Borneo using tan 

 barks from the .same species of mangrove as those found in 

 the Philippines. These factories regard the process of manu 

 facturing cutch as a trade seci-et, but we cannot believe that 

 ■these so-called trade secrets are of a very formidable nature, 

 as we have succeeded in preparing very good grades of cutch, 

 without any complicated proce.sses. 



The following was the method used to prepare the cutch: 

 The tinely ground bark was leached with cold water, and this 

 solution evaporated to drjness in, vacuo. Hot water extracts 

 too much of the colouring matter, and no more tannin than 

 cold water. Tlie evajjoration, at least the latter stages, must 

 always be made in vacuo to avoid burning the cutch. It is 

 sufficiently obvious that the extraction on a large scale would 

 ■be carried out in such a manner that strong solutions would 

 be employed to leach fresh barks, while weak ones would 



be used to extract the last percentages of the tannin from the 

 jiartly exhausted bark. All the parts of the factory, except 

 the vacuum driers, could be built on the grjuud, and it is 

 evident that the fuel for the boilers and for the driers \viiuld 

 cost very little, so that it would ajjpear that, if the cutch 

 manufacture were taken up in connexion with the lumbering 

 or firewood industry, it would be exceedingly pirofitable. 



The Annudl Rejiort of the Board of Af/riruliun:, 

 Jamaica, 1907-8, gives information as to determinations 

 of the tannin content of several Jamaica mangroves, 

 which were made by the Island and Agricultural 

 Chemist. From this, it would appear that the Jamaica 

 mangroves compare well, as a source of tannin, with the 

 plants that are dealt with in tlie above-mentioneri 

 publication. 



WAYS IN WHICH BACTERIA INFECT 

 PLANTS. 



Bulletin No. 28 of the Division of Biology of the 

 New Zealand Department of Agriculture, entitled 

 Bacterial Dl-'^eases of Plants, deals with ways in which 

 bacteria infect plants, thus suggesting methods which 

 may be employed to previ-nt, or minimize, the chances 

 of such infection : — 



The study of the various ways in which infection of the 

 host plants is secured is especially valuable in devising means 

 for the control of disea.se. In the case of bacterial diseases, 

 wound-infection is very general, and in this process, insects 

 play a very large part. In inoculation experiments, the 

 bacteria are introduced into the tissues of the host by means 

 of minute needle-pricks, and this constitutes typical wound- 

 infection. In nature, infection may be divided into two clas.ses : 

 that which takes |)lace on those jiortions of the host that are 

 below the surface of the soil, and that which takes place on 

 those portions of the host above ground. To the former 

 category belong such diseases as the wet-rots of potatos and 

 other tubers, and to the latter, bacteriosis of potato, black- 

 rot of cabbage, wilt of cucumbers, pear-blight, etc. 



With regard to underground infection, wounds are in 

 nearly all cla.sses directly responsible for the entrance of the 

 di.sease-gerni, but the physical condition and water-content of 

 the soil play an inipirtant part, for it is in badly aerated, 

 sour, water-logged soils that these wet-rot producing bacteria 

 are chiefly to be found. The action of those insects and 

 animals causing wounds on the underground portions of 

 plants will greatly aid the spread of such bacteria through 

 potato and other root crops. 



In aerial infection the aotion of insects is most marked. 

 In jiear-blight, bees and other insects, in collecting from 

 diseased ttower-clusters, will rapidly spread the disease to all 

 the healthy flowers they may visit. This method of infection 

 is also analogous to wound-infection, inasmuch as the stigma 

 on which the bacteria may lodge represents to all intents and 

 pur|ioses a wounded surface. It has been definitely proved 

 that the potato bacteriosis (/Jacillu.f solanaccannn) k trans- 

 mitted from plant to plant by leaf eating beetles, and in 

 conse(|uence, if this disease is to be checked, these beetles 

 must be kept well under control. 



The same remarks a[iply to the black-rot of cabbage 

 (I'lsiiudoraonas fanipe^(ris) ; but in this case infection can also 

 take place through the water-pores that are situated on the 

 edges of the leaves. The wilt of cucumbers (liaciUns trnch- 

 ei/ihi/us) is likewise transmitted by leaf-eating beetles, so 

 that in greenhouses it should be a simple matter to keep 

 these in check, and at the same time avoid the danger of 

 infection. 



