Vot. XVIII, No. 456. 



THE AGRICULTURAL NEWS. 



■^I^i 



We have referred to the effect of common s^lt 

 upon the process of transpiration in halophytes. It 

 is probable that an opposite effect is produced 

 in the case of non-ha!oph\-tes. 



In regard to the fonner cias.?, investigations des- 

 cribed by T. H. Hill have .shown that the aerial parts 

 of halophytes can absorb both fresh and aea-water, and 

 thus can take advantage of any rain, dew, or sea-water 

 which may wet such regions. Halophytes can also 

 absorb moisture from the atmosphere, and finally, 

 during drought some parts of a plant can be kept alive 

 at the expense of water in other parts. It is improb- 

 able that these characteristics occur in the case of the 

 coco-nut and sugar-cane, except perhaps, in regard to 

 the last-mentioned feature. 



Concerning photosynthesis, or the building up of 

 carbohydrates by green leaves in sunlight, Palladin (^) 

 states that excess of salts in the soil has a retarding 

 effect ujion this process. Watering wich sodium 

 chloride solution caused development to cease in most 

 plants (non- halophytes), through the checking of 

 photosynthesis. It is also due to stomatal closure, 

 caused by excess of salts. If the leaves are slightly 

 Wounded so as to facilitate entrance of carbon dioxide 

 into the tissue, starch accumulates about the wound 

 m^gins. True halophytes grow, though slowly, upon 

 soils rich in salts, since their stomata do not close 

 at all. 



The main conclusions arrived at from the fore- 

 going are information that the roots of plants that 

 require common salt or may be subjected to salinity 

 without injury, can adapt themselves physiologically to 

 changing conditions of salinity. This i.s particularly 

 true of halophytes : it is probably true of .such a 

 plant as the sugar-cane; it is certainly true jf thi? 

 coco-nut, which may be described as a facultative halo- 

 phyte. As regards such plants as cotton and sweet 

 potato, which are commonly seen cultivated on land's 

 adjoining the sea, there is no available information, 

 The effect of salt in maritime plants is not to reduce 

 ab.sorption and transpiration of water. In the case of 

 non- maritime plants there is a distinct tendency to 

 reduce absorption, transpiration, and photosynthesis. 

 The effect of common salt is greatly modified by the 

 presence of other substances in the soil-solution. 



(1) K. B. Copelaud : 'The Coco-nut (1914)'. 

 ' (•-) T. H. Hill : 'The Wiiter Econoiuy of Maritime Plants", 

 Science Prog es.<, .Jul}' 1019. 



• ' (■■) .1. B. Harrison aivl F. .V. Stcckdalc,. Wesi TiiJiaii 

 Btilldin, Vol. XIII. 



i(*-.) F. W. Zei-lian, 'The Salt Maishe.s of the North Coast of 

 Povto Rico.' BaUetiu Nu. .}, Experiment ,Sl«Uion of the 

 Siiiiai- Producers Association of Povto Kico (iyi3). 

 (■■) Palladia's Plant Pysiology, p. 36. 



Recent Exports from British Guiana — 

 The following figures, published in a recent issue of the 

 pemerara Dii//v Argi'sy, are interesting. A large increase 

 in the exports of ui>st products for this year's period will 

 be noticed. One exception, however occurs in the case of 

 rice. In this connexion the reader is referred to a note on 

 the export of rice from Briti.sh Guiana. on thf- Gleanings ptge- 

 of this issue : — 



The Dominica Report. —The following appreciatire 



statement appeared in a r- cent i.ssue of the Port of-SpitiU 

 Gazette (Trin dad). The Report on the Agricultural Depirfr- 

 •01 lit, Dominica, for the year ended March 31 1919, is to 

 hao.i, and to us is certainly the best report issued in the 

 Nolhern Islands for .some years past. Considering that .\It. 

 Joseph Jont-s, the able (-^untor, was, so to speak, single* 

 handt'd for some time "wing to Mr. G A. Jones, .Assistant 

 Curator and Chemist, (who is now in the employment of the 

 U.S.M. authorities down south) having left Dominica in 

 19.17 to undertake war woik in Enghan'i, a most credit*hle 

 record is shown. The Rt-port. unlik«? m.iQy similar rt^-nrcja 

 which are invariably dry as dust, is nndombfedly . worthy of 

 perusal aoil study. 



