ToL. Xir. No 280. 



THE AOnrCULTURAL NEWS. 



23 



BOLL-SHEDDING IN COTTON. 



The following information refers not only to the 

 shedding of the bolls of cotton, but also to the dropping 

 of the leaves, flowers and buds bufore niaturity. It is 

 taken from The Cotton Plant in Egypt, by W. L. 

 Balls, M.A., which wa.s reviewed in the Agricultural 

 K( trs, Vol. XI, No. 278. The greatest attention is paid 

 to the shedding of boils, in the West Indr. .'-, where it 

 is recognized that this follows suddeti changes in the 

 veather conditions surrounding the plait. 



The act of shedding i.«, of course, un'^er the control of 

 the plant, its immediate cause being the fonii.ation of a special 

 tissue across the ba.^e of the stalk of the leaf, bud or Hower. 

 The facultative position of this ti,«sue, or 'absciss-layer', is 

 marked by a slight groove on the stalk. When the determin- 

 ing stimulus has been received by the eel's of this layer, 

 vhich are otherwise indistirguishable from their neighbours, 

 they proceed to divide, and the daughter-cells separate from 

 one another, thus destroying the continuity of the stalk 

 except in such tissues as the wood. The phloem being among 

 the severed tissues, synthesized food-supplies are cut off, the 

 organ dies, sooner or later tie stalk breaks, and the organ 

 is shed. Eren before any sign of unhealthiness becomes visi 

 lile, the stalk may break at a light touch, being retained 

 merely by the wood vessels, bast fibre,', and cuticle. 



The reaction to the determining stimulus is very rapid in 

 cotton, on account of the extreme simplicity of the absciss- 

 layer. A convenient way of provoking" this unknown stimu- 

 lus is to cut off a few roots. Within four days after such 

 treatment, we find that complete severance of the tissues of 

 tht absciss layer has taken place. Microscopic exunination 

 at intermediate stages shows that the plate of dividing cells 

 is only one cell thick, that the division begins at the 

 periphery, and extends towards the centre, and that the 

 dividing wall between the daughter-cells .splits immediately 

 along its middle lamella. The daughter-cells which are left 

 on the face of the scar, after the stalk has broken away, 

 •bulge outwards, and form a simple c.dlus. 



In many plants this stimulus is also provoked by non- 

 pollination, so that unfertilized flowers are shed. This occurs 

 in cotton, of course, but it df^es not seem to be common under 

 ordinary conditions. 



For the present we are unable to form any clear concep- 

 tion of the chain which extends from the severed root to the 

 absciss-layer. It is certain that the main factor, if not the 

 only one, is the water content of the plant. Mere severance 

 of the root does not provoke shedding as a traumatic stimulus 

 [stimulus arising from wounding]; thus, plants w'hich are 

 Screened from direct sun after the root has been damaged, 

 «Low little or no shedding. Consequent on such root damage 

 «u find a general closure of the .itomata, and it seems at least 



probable that this abnormal closure reacts first of all on the 

 absciss layer, by bringing about abnormal internal tempera- 

 tures. Much more experimental work is required before- 

 further discussion can be profitable. 



Thi>ugh the primary cause of shedding in E^ypt i» 

 a deficient root absorption, it follows that an excessive trans- 

 piration rate must produce the same result, since the terms 

 'deficient' and 'excessive' are relative .\ very dry hot day 

 may provoke shedding, but such weather is infrequent at the 

 time when shedding is important,. The heavy .shedding of 

 wide-sown plants as compared with that of plants in field- 

 crop is probably caused by excessive transpiration, or rather,, 

 by too great irregularity in this function, since wide-sowa 

 plants are freely exposed to wind, and do not create a humid 

 'surface climate'. In the Sudan, however, spells of hot dry- 

 wind are generally recognized as being th-; precursors of 

 shedding epidemics. 



DEPARTMENT NEWS. 



The Imperial Commissioner of Agriculture left 

 Barbados by the R.M.S. Trent', on January 13, for an 

 official visit to St. Lucia. Dr. Watts is expected to 

 return by the S.S. 'Koroua' on January 2-5. 



Mr. F. W. South, B.A., Mycologist to the Depart- 

 ment, left Barbados for Montserrat by the R.M.S. 'Treni' 

 on January l.S, in order to make investigations regarding 

 plant diseases in that island. 



Sisal Hemp in German East Africa. — 



H.M. Vice-Consul at Dar-es-Salaam reports that, according to 

 the local press, the cultivation of sisal hemp in German East 

 Africa yields a crop second only to rubber in importance to 

 the Protectorate. The plant was introduced into the country 

 from Central America some fifteen years ago, and the export* 

 of fibre have increased from 204 metric tons in 1901 to 

 7,228 metric tons valued at £150,569, in 1910. The plants 

 attain full growth in East Africa in ab"Ut seven years, buff 

 the first leaves can be cut after three years' growth. In 

 1911 there were 19,050 hectares (about 47,039 acres) planted 

 with sisal in German East Africa, of which 7,G55 hectares 

 (about 18,901 acres) were productive. The majority of the 

 sisal plantations are in the northern districts in the Tanga 

 hinterland, where about 1(),000 hectares (about 39,506 acres) 

 are planted. There are about 2,000 hectares (about 4,938 

 acres) in the district of Lindi, to the south, and plantations 

 have recently been formed near the railway running from 

 Dares-Salaam to Taborah. {7'he Board of Trade JoTirnalf, 

 December 5, 1912.) 



A curve given in the Semi-annual report of Messrs. 

 Schinimel A: Co., dated October 1912, showing the average 

 prices of Ceylon citronella oil from 1892 to 191 1-12, in pence 

 per pound c.i f. London, indicates that these remained just 

 above \0d. until 1894, after which year they gradually rose 

 until in 1896 they were just above lid. There was then 

 a gradual drop until 1902, when they were 8jrf. A quick 

 ris" brought them to 18]rf. in 1^06, and then there was 

 a gradual fall until the beginning I'f last year to just under 

 11(/. Since thit time, there has been a quick increase which 

 brought them to \6\d. in .August 1912. In this informatioa 

 the term 'average prices' means the average of the monthly 

 prices of each year. 



