:i94 Journal of the Department op Agriculture. 



The Weeds of South Africa. 



A fiirtlier contribution to that most useful series of articles on 

 " The Weeds of South Africa," by Dr. Pole Evans and Miss K. A. 

 Tiansdell, of the Division of Botany and Plant PaHiolog-y, has now 

 been ])ublished. and is obtainable, free of charge, on application to 

 this otfice. It comprises the followino' articles, viz. : (x) The Sow 

 Thistle (Bulletin No. G, 1920), (xi) The (ialinsoga Weed (Bulletin 

 No. 7, 1920), (xii) The Upright Star-bur (Bulletin No. 8, 1920), (xiii) 

 The Purple Stinkweed (Bulletin No. 9, 1920). 



Like the earlier publications, the above are composed of a 

 coloured i)late illustrating the weed and its various parts, together 

 with a description thereof and advice as to the best methods of 

 eradication. The prevalence of weeds in the TTnion is a matter of 

 economic importance, and the purpose of these bulletins is to enable 

 farmers to recognize the presence of dangerous weeds on their farms 

 and advise them how to extirpate them. The weeds dealt with in the 

 series of bulletins published prior to the above are as follows, and are 

 also obtainable from this office : — 



(i) The Mexican Marigold, Khakibos, oi' Africander Bosie (L.S. 

 No. 33); (ii) The Malta Thistle (L.S. No. 35); (iii) The Burweed or 

 Boete-Bosjie (L.S. No. 36); (Tv) The Mexican Poppv (L.S. No. 37); 

 (v) The Dwarf Marigold (L.S. No. 38); (vi) The Khaki Weed (L.S. 

 No. 73); (vii) The Cockle-bur or Ranker Roos (L.S. No. 74); (viii) 

 The Jointed Cactus (L.S. No. 75); (ix) The Imbricate Cactus (L.S. 

 No. 76). 



African Horse-sickness. 



A valuable article by Sir Arnold Theilei , K.C.M.C, Director of 

 Veterinary Education and Research, on African Horse-sickness has 

 jiist been published by the Department.* It reviews all our 

 knowledge of this dreaded disease and gives a concise account of the 

 problem as it stands at present. Every farmer should secure a copy 

 of this bulletin and study it carefully. For the benefit of those w'ho 

 may find the subject-matter lather too technical, this short summary 

 is given. 



The introduc-tion contains an interesting historical survey of the 

 disease. It seems that horse-sickness was recognized in East Africa 

 as early as the year 1569. In South Africa very severe outbreaks are 

 on record at various intervals, e.g. in the years 1719, 1780, 1801, 

 1819, 1839, 1854, etc. Within recent years some very heavy out- 

 breaks have again occurred, notably those of 1913-14 in Uitenhage, 

 Humansdorp, and adjacent districts, 1918 in Clanwilliam, 1920-21 in 

 Herbert and adjoining districts. All these outbreaks can indirectly 

 be ascribed to peculiar climatic conditions that prevailed at the time. 

 These conditions are discussed in the article. 



The actual cause of horse-sickness is a virus, which is so small 

 that it is invisible under the highest power of the microscope. A 

 close study of the way in which the disease is contracted and sjjreads, 

 leads to the conclusion that a blood-suckinff insect is the carrier. All 



*" African Horse Sickness," Science Bulletin No. 19, obtainable from this office, 

 price ;^d., prepaid. 



