iNQUIlilES AND REPLIES. 281 



Nitrates ver.svs Legumes. 



Swaziland. — I think my soil needs fertilizin<j;', and I was con- 

 templating- buying some nitrates. How would you recommend me 

 to use these? 



Potchefstroom ScJtool of Agriculture replies : Nitrates alone 

 applied on your soils will rarely be profitable. They will help to 

 stimulate leaf growth on a forage crop, but will not benefit grain 

 production. You can also get increased leaf growth more cheaply 

 by planting your barley or oats on a land that has just carried some 

 legumes. The greatest need of our soils is phosphates, and if you 

 Avant to buy and try something, buy superphosphate. This will give 

 you far more satisfaction than nitrates. Until tlie phosphate content 

 of your soil is improved you can expect little benefit from nitrates. 



Die-Back in Roses. 



Aliival North. — I am enclosing two specimens of branches of my 

 rose trees, and should be glad to know (1) what is the matter with 

 them ; (2) how to control the disease, if any ; (8) whether other trees, 

 e.g. vines, are likely to become infected. 



The Division of Botany replies : The specimens of rose twigs 

 submitted are infected with a fungus disease probably due to the 

 organism Coniothyrimn fuckelii. The disease is spread by means of 

 the fungus spores which are blown about and infect the jilant through 

 wounds, resulting in a " die-back " o£ the part affected. Control 

 measures consist in cutting away and burning all diseased and dis- 

 coloured wood, painting over cut surfaces, and spraying all plants 

 Avith some good fungicide, such as bordeaux mixture or lime-sulphur. 

 Care should also be taken to use only cuttings from healthy plants. 

 Infection might be carried by using an apparently healthy cutting 

 from a diseased plant. The disease appears to attack all kinds of 

 roses, but is not known to occur on other plants. 



Wild Cotton. 



Bloeinliof. — 1 enclose a sample of wild cotton that was gathered 

 from the pod of a plant known as "melkbos." Tlie plant is very 

 common in these parts, and I should be glad to know whether the 

 cotton has any value. 



Tlie Division of Botany replies: The " wild cotton" consists of 

 the seed-hairs of the plant known botanically as Asclepias fruticosa. 

 This plant is a member of a large family of plants, all of which are 

 characterized by liaving long silky hairs attached, parachute fashion, 

 to the tips of the seecl.s, and the greater number by having milky 

 juice. The "cotton" or floss from these plants was submitted to the 

 Imperial Institute for investigation as to its economic and commer- 

 cial value. The report received was not at all favourable. The floss 

 is useless for weaving purposes, and for the filling of pillows, etc., it 

 cannot compete either for resiliency or for cheapness of production 

 with other vegetable downs, such as kapok, already on the market. 



