Eumycetes. — Pflanzenkrankheiten. 51 



Winge, Ö., Encore le Sphaerotheca Castagnei Lew (Bull. Soc. 

 myc. France. XXVII. p. 211—219. PI. VII- VIII. 1911.) 



L'oogone renferme deux noyaux quand rantheridie contknt 

 encore un noyau non degenere. L'auteur n'a pu observer la divi- 

 sion d'oü proviennent, ä son avis. les deux noyaux do l'oogone. 

 Ceux-ci ne se fusionnent jamais. L'unique l'usion s'aecomplit entre 

 les deux no) T aux de l'avant-derniere cellule de l'ascogone, d'oü pro- 

 cede l'asque. Les filaments recouvrants naissent, non seulement du 

 pedicelle de la cellule femelle, mais aussi de la cellule qui porte 

 rantheridie. Ce dernier fait avait et£ signale par Harper chez le 

 Phyilactinia, non chez le Sphaerotheca. 



L'auteur a constate le rapprochement des centrosomes au mo- 

 ment de la fusion nucleaire, ainsi que la division centrosome du 

 noyau de l'asque et l'ecartement des deux centrosomes- fils au mo- 

 ment de la premiere division. P. Vuillemin. 



Pole-Evans, J. B., South Afriean Cereal Rusts, with obser- 

 vations on the problem of breeding rust-resistant wheats. 

 (Journ. Agric. Science. IV. 1. p. 95 — 104. 1911.) 



Cereals which are rust-resistant in oiher countries do not retain 

 this quality when introduced into South Africa, where the rust- 

 problem is very serious. 



The varieties of rust hitherto noticed are: 



1) Puccinia graminis, Pers., Black rust on wheat, Barley, Oats 

 and Rye. 



2) Puccinia triticina, Ericks. The Brown rust on Wheat. 



3) Puccinia covonifeva , Klebahn. The Yellow rust on Oats. 

 X Puccinia dispersa, Ericks. The Brown rust on Rye. 

 Puccinia graminis is the most serious of these rusts, and is 



also found on Dactylis glomerata, Loliurn temulentum and Festuca 

 elatior. So far no aeeidial stage is known in South Africa, but 

 only the uredo and teleuto stage. 



Three forms of P. graminis on cereals oeeur: 



a) The form oecurring on Rye which also infects Barle} 7 but 

 not Wheat or Oat. This only affects the stalks, all attempts to infect 

 rye leaves having so far failed. 



b) The form on Wheat infects Barley, but neither Rye nor 

 Oats. During the winter months the Barley, is immune, though 

 Wheat growing alongside may be badly rusted. Barle)^ is highly 

 susceptible during the summer. 



c) The form on Oats, which does not affect Wheat or Barley. 

 Rust in oats is unknown in India, but Indian oats grown in the 

 Transvaal are highly susceptible to both P. graminis and P. 

 coronifera. 



Attempts are being made to test rust-resistant wheats, on much 

 the same lines as Biffini's work in England. It appears that the 

 hybrid resulting from a cross between an immune and susceptible 

 plant, becomes even more susceptible to the Black rust {P. graminis) 

 than the susceptible parent, possibly because since the hybrid is 

 more vigorous than either parent, it affords a larger food supply to 

 the rust. Further, the rust from the hybrid is able to infect the 

 immune parent, and also produces a severer infection on the sus- 

 ceptible parent than rust from the parent itself. In other words, the 

 pathogenic properties of the rust are distinctl}' increased alter its 



