"Vol. IX. No. 201. 



THE AGRICULTUKAL NEWS. 



13 



STUDENTS' CORNER. 



JA-XUAKV. 

 FiEST Period. 

 Seasonal Notes. ; 



Now that ciitton-pieking is in progre-ss, a good oppor- 

 tunity is ati'orded for studyiug the fruit- and seeds of the 

 plant, and the lint which is yielded by it. Collect a number 

 of bolls, at various stages of opening, and^compare them with 

 the unopened bolls that you lutve e.vamined already. In con- 

 nexion with the development of the bolls, Ivhat action has the 

 cotton flower bud maggot, which causes the serious reduction 

 in yield thit follows attacks by this pest .'-Find out whether 

 the lint grows out from the fruit-coverir;g»or from the seeds, 

 and compare its development with that of the pulp in an 

 orange. In young, unopened bolls, the lint contains liquid 

 matter. How is this wthdrawn when the boll ripen.s, and 

 what ett'eot has this withdrawal in connexion with a useful, 

 characteristic property of the lint; Study the effect of 

 disease on the bolls, cutting them through in order to find 

 out what, if anything, is happening to the lint. (See A'/ri- 

 ridtural JS^ewx, Vol. VIII, p. 290 and references there given.) 

 Distinguish between fungoid and bacterial diseases of cotton. 

 It often happens that cotton plants suddenly commence to 

 drop bolls in large numbers, while the reason for the circum- 

 stance cannot be traced to the action of any definite pest. 

 State broadly how a cause may be assigned for this boll- 

 dropping. 1 



With reference to the yield of lint, comparisons should 

 be made in the matter of the amounts tliat arc obtained from 

 different pickings. Does the first or subsequent [lickings give 

 the largest amount ', Is there any difference in the quality 

 of the product from different pickings ? The amounts of lint 

 from the different fields should be carefully recorded, and the 

 differences in quality, if very marked, .should be noted. These 

 facts should be brought into relation with the history and 

 state of the soil and the crops in the fields: in this way, useful 

 information will be obtained with respect to the following 

 points, among others: the best soils for cotton; the effects of 

 cultivation and the use of the different manures; the impor- 

 tance of good drainage; the necessity for the removal of old 

 ■ cotton plants, after picking; the results from the use of 

 different strains of seed (where these have been employed), 

 as regards yield, quality, and resistance to disease; the 

 relation between yield of lint and the e.xtcnt to which attack 

 by diseases and pests has taken place. 



It is convenient to draw attention here to the way in 

 which what has been stated in the last paragraph illustrates 

 the necessity for constant observation and recording of results, 

 if the observer is to be put into possession of facts that are 

 really useful. If observation has been neglected at almost 

 any stage, or if the results have been imperfectly recorded, 

 their proper interpretation may be rendered impossible, or at 

 least, made incomplete. It must not bo thought that work 

 of this kind can only be carried out with such a crop as 

 cotton; those who are not directly interested in this crop can 

 make similar observations, with similar precautions, in 

 the ca.se of tlie one with which they have special concern. 

 It so happens that cotton is a particularly useful plant for such 

 ■work, chiefly because both the quantity and the quality of 

 the produce that is required from it can bereasily determined. 



Those students who are interested in cotton are 



reminded that they should now obtain practice in judging 



lint by pulling it from the seed in the way mentioned in the 



West Indian Bulletin, Vol. VII, pp. 162, 163; practical 



• assistance in this matter may be obtained from the officers 



of the Botanic Stations. 



Eemember that cotton for shipment must be carefully 

 graded; that is to say the produce from various pickings must 

 not be mi.\-ed, and that all staine^ Cotton must be carefully 

 kept separate from the rest. Jnlbrmation on this subject 

 i.s contained on page 31i of Volumi VII of the Ayrirnltaral 

 Keti's. 



Questions for Candidates. 



PRELIMIX.iRY QUESTIONS. 



(1) Why is it desirable to sQ^k sugar-cane cuttings in 

 Bordeaux mixture i 



(2) What are the principal objects nf pruning? Com- 

 pare the results of frequent light, and occasional heavy, prun- 

 ing of a cacao tree. 



(3) What nitrogenous manures are chiefly used for 

 ratoon canes ? State whence their nitrogen is derived. 



INTERMEDIATE QUESTIONS. 



(1) How is water retained in soil, and how does the 

 method of its retention admit of the simultaneous presence 

 of air and water ' 



(2) Wliat do you understand by the rotation of crops ? 

 What useful purposes are served thereby ? 



(3) Give an account of the uses that can be made of 

 cotton seed. 



RUBBER TREES AND GREEN MANURING. 

 A circular has recently been issued, by the Direc 

 of Agriculture, Xyasaland, dealino; with greet 



tor 



green 



manuring in the tropics. The following passage from 

 this circular, having relation to the subject in connexion 

 with rubber, is of special interest: — 



It lias been proved that the flow of latex: from a rubber 

 tree is affected by endosmotic pressure, which practically 

 means the amount of water in the plant roots. It is the 

 practice to tap rubber in the early morning and evening, and 

 to discontinue during the heat of mid-daj- and early after- 

 noon. During the heat of the day much water is evaporated by 

 the leaves, and latex flows slowly, but in the early morning and 

 evening water wishes to enter by the root quicker than it is 

 evaporated, with the result that there is an internal pressure 

 which helps the flow of latex; therefore it is practical to 

 assume that there is an intimate connexion between the 

 presence of water in the surface soil surrounding the roots, 

 and the flow of latex from the rubber tree. For half the 

 year in Nyasaland there is no rain, and daily the sun is 

 strong enough to evaporate water from the plants and from 

 the soil. The question arises, where does this water come 

 from .' The answer is, from the lower' layers or subsoil, by 

 rising to the surface in the form of water vapour and water 

 liquid (capillarity). In the surface soil of a clean-weeded 

 estate the water during the day is principally in the form of 

 water vapour, the water being vaporized to a considerable 

 depth by the direct, overhead rays of the tropical sun. In 

 the surface soil of an estate growing a green manure crop, 

 there is a large proportion of the water in the liquid form, as 

 the covering of vegetation reduces the temperature of the 

 surface .soil, and prevents the direct penetration of the sun's 

 rays. Therefore, when rubber is growing surrounded with 

 vegetation, its roots have actual access to liquid water through 

 the greater part of the day. If we examine the same soils? 

 during the dry season after the green manure crop is dead, 

 we still find more moisture in the latter, as the dead remains 

 of the green manure crop absorb and retain water more firmly 

 than ordinary soil, but deliver it freely to the rubber roots, 

 although n.jt as freely as to the atmo.sphere. 



