I'KI-.SlDKNTlAr, .\i)l)RI-:SS SluTION C. ](X) 



A. Wheat is attacked by two distiiicl rust iwv^i : 



I. I'Ik' l^)lack Rust, Pitccinia (/raiiiiiiis IVrs. ; and 

 J. riu' U'-own K'ust, riicciiiia In'liciiia Rriks. 



H. ( )ats arc attacked I)y — 



1. The Bhick Rust, Fuccinia (jra minis Pers. 



2. The Yellow Rtist, Puccinia Lolii Nielsen. 

 C". Rye is affected by two distinct rusts — 



1. The Black Rust, Puccinia gratninis Pers. 



2. The Brown Rust, Puccinia disf^crsa Kriks. 



D. Barley is attacked by — 



I. The Black Rust, Puccinia (iraniinis I'ers. 



E. Maize is subject to two rusts — 



1. The Brown Rust, Puccinia niaydis Bereng. 



2. The Red Rust, Puccinia Sorf/hi Schw. 



Two very common and widespread rusts, Puccinia (jluniarnnt 

 and Puccinia simplex, the former occurring on wheat, barley, 

 and rye; the latter, on barley, have tiot, so far as I am aware. 

 l)een detected yet on these cereals in South A.frica. The explana- 

 tion for this cannot yet be given. It seems hardly possible to 

 l)elievc that if they did occur here they could have esca])ed obser- 

 vation. 



Only the uredo and teleuto forms of P. gravAinis, P. Iriticina. 

 P. Lolii, and P, dispersa are known in South Africa. In Europe 

 the ?ecidial stage of P. graminis is on Bcrheris vulgaris; of P. 

 Lolii Nielsen it is on Rhamnus catlwrficus. 



In South Africa it does not seem that the ?ecidial host is 

 necessary or is ever secured in the case of these species. In 

 endeavouring to account for the sudden outbreaks of disease. 

 I am firmly of opinion that over-wintering uredospores cannot 

 be held entirely responsible. The fate and subsequent history of 

 the teleutospores in this country still await elucidation. 



In the case of one of the maize rusts (P. maydis) we have 

 a more complete picture of events, although one of the spore 

 forms — the spermatia — still remains a mystery. Indeed, Puccinia 

 maydis is the onl}' hetercecious rust at ]:)resent known in Soutii 

 Africa. 



I succeeded in 1911 in establishing the fact that £ecidiosjX)re< 

 from O.valis corniculata readily infected maize and ])roduced the 

 rust Puccinia maydis; while teleutospores of Puccinia maydis. 

 ■vhen sown on Oxalis corniculata, brought forth typical jecidia in 

 eight to ten days. 



These experiments were repeated for several years with the 

 same result, except that during the season 1913 inoculated plants 

 of Oxalis ])roduced practically nothing else but s])ermagonia 

 Vv'ith their attendant spermatia. This remarkable i)henomenon 

 would, I think, more than repay following up, and would ])erhai)s 

 furnish a clue as to the exact nature and pur])ose of these most 

 })uzzling bodies. 



