Vol. XII. No. 296. 



THE AGRICULTURAL NEWS. 



2iio 



STUDENTS' CORNER. 



SEPTEMBER. . 

 Fir.sT PEnioD. 

 Seasonal Notes. 



REVIEWING THE SEASON'S COTTON PRICES. 



At this time of the year the intermediate and 



final 



student will derive benefit by referring back to the notes on 

 West Indian cotton in the past numbers of the current 

 volume of the Aijricultural Ndvs, with a view to tracing the 

 rise and fall of cotton prices in luigland and the United 

 States. A useful procedure would be to plot the values on 

 squared paper, making the units of the vertical axis pence, 

 and those of the horizontal axis, tlie dates 

 at which these prices ruled. Four graphs should 

 be plotted: (1) St. Vincent (superfine) cotton; 

 (2) General (fine) Sea Island cotton; (.'?) Extra 

 Fine American Sea Island; and (t) Fully 

 Fine American Sea Island. 



A3 regards West Indian cotton, ;i steady 

 rise will be observed to have occurred during 

 !March. There was a drop towards the end 

 of April, however, and a steady fall of general 

 West Indian during May and .lune. Super- 

 fine Sea Island will be seen to have remained 

 very firm during the past three or four 

 months, and on .lune .30 some bales were 

 sold at 'iOd. per lb. About that time, how- 

 ever, some medium West Indian Sea Island 

 dropped below the American Extra Fine value 

 (16t/. per B). on June 17). This, however, 

 appears to have been the only occasion when 

 West Indian and American prices have 

 touched. 



USEFULNES.S OF (iEAPHS. 



While speaking of graphs, it may be sug- 

 gested that the student should employ^ 

 this form of record more generally than 

 is the usual custom on the estate. 

 Plotted curves are simple, and make 

 very small demands as regards time and 

 trouble. They show relations and temlen- 

 cies far more clearly than figures in a list 

 or table, and they can always be con- 

 veniently extended from time to time, 

 and be easily filed for future reference. 



Those who are unacquainted with the 

 details of graphical methods should pur- 

 chase the small handbook on the sub- 

 ject by Hall and Stevens. (Price Is.) 



Although the rate of the rise of moisture varies in soils 

 and plants, it is probably a much simpler phenomenon in the 

 soil, being in this case almost entirely the effect of surface 

 tension. In the plant, capillarity is certainly one factor 

 involved in the ascent of sap; but there is also the influence 

 of the stoniata in the leaves and morphological features, 

 together with the varying densities of the fluid contents 

 of the cells. In other word.-, osmotic pressure and the general 

 individuality of the plant have to be considered. Do not 

 forget, however, that recent researches have shown that osmosis 

 occurs in soils as well as ia plants. (See Ayrindtural Xtws, 

 current volume, p. 120.) 



Questions for Candidates. 



I'liELI.MINARY (iUESTION.S. 



(1) What do you know concerning the physical and 

 chemical composition of soils suitable for rubber growing' 



(2) Name a useful mixture f'lr spraying 

 cacao thrips. Mow would yon proceed to 

 make it, and to apply it.' 



INTl:i:.MEDIATE QUESTIONS. 



(1) Discuss calcium cyanamide (a) as 

 a manure, (b) as an insecticide, (c) as regards 

 its manufacture. 



(2) Describe in non-technical tsrms, any 

 practical application of Mendelism you are 

 acquainted with. 



FINAL QUESTIONS. 



(1) Discu.5S manganese as a soil constit- 

 uent. Compare its action with that of iron. 



(2) State your views in regard to the 

 disinfection of hides. To what extent does 

 (a) the island you live in, (b) the West 

 Indies, export these articles? 



Fit 



17. Water Rises in 

 A Plant — 



FiG. 18. And 



THE RISE OF WATER IN SOIL> AND PLANTS. 



Soil Temperature in Its Relation to 

 Plant Growth. — The following interesting 

 account of a paper on this subject, taken from 

 the E.rjieriraeiit Station Ricord (July 

 191.3) is of interest in connexion with 

 observations of a somewhat similar nature 

 made some time ago in the West Indies: — 

 This article [under review] gives inves- 

 tigations on the above subject, discussing 

 particularly soil temperature as a plant 

 biological and geographical factor, the 

 relation of soil temperature to phenologi- 

 es cal phenomena, the influence of geogra- 

 f/^phical position and sealevel upon vegeta- 

 -"tion and soil temperature, anil the rela- 

 tion of the coming of spring to a tempera- 

 ALSO IN TiiK Soil. ture of 10°C. in the soil and the duration 

 of sunshine. The author concludes that there is a direct relation 

 between soil temperature and the coming of spring. A defi- 



Turning from these economic ■ onsiderations to others 

 connected with agricultural chemistry, an interesting 

 reflection is to contrast the difference between the rise 

 of water in the soil and that in a growing plant. In 

 each case water ascends at different rates according to 

 the kind of soil, and according to the kind of plant. This 

 can be shown by conducting experiments by means of the 

 simple, homemade apparatus shown in Figs. 17 and 18. 

 Details concerning the working of this apparatus must be 

 obtained from local sources, or from a book on elementary 

 agricultural chemistry: {XtMare ?'<■,),•/" /'^ would be a suitable 

 source to refer to). 



ciency of TC. in the average soil temperature at depths of 

 from i to 1 metre in March and April delays spring ten days. 

 The blooming of apples coincides closely with the appearance 

 of a temperature of lO'C. in the soil at a depth of i-metre. 

 A decrease in the average daily duration of sunshine of one 

 hour during the winter lowers the temperature of the soil 

 during March and April 3'C'. and delays spring one month.' 

 In the Tropics, of course, this seasonal influence does not 

 exist to the same extent. It may be noted, however, that in the 

 West Indies, an annual variation of a few degrees occurs in re- 

 gard to soil temperature in the so-called winter and summer 

 months; but of course, the main factor affecting the stimulation 

 of growth is the amount of moisture present. 



