RESISTANT PLANTS. - DISEASES OF VARIOUS CROPS 



1543 



and nature of physiological races in Erysiphe graminis, and further shows 

 that the degree of susceptibilit}' of the various varieties and species differs 

 considerabh\ for it is possible in a limited number of cases to give rise to 

 a perfectly immune condition. In such a case, the inoculation of conidia 

 from the parasite produces no effect, or, at the most, it causes little disco- 

 loured patches to appear on the foliar limbs. In the susceptible varieties 

 the mycelium develops 2 or 3 days after inoculation in obvious patches 

 which join together often to the extent of covering the leaves and stems 

 with a continuous layer of mycelium ; on this layer conidia soon appear in 

 considerable quantities. 



1 126 -Experiments on the Wintering of the Teleutospores of "rust" in Grasses.— 



KleB;VHN, H., in Zeitschrift fiir Pilanzenkrankheiten, Vol 26, Fa-c. 5, pp pp 272-277, 

 Stuttgart, July 30, igi6. 



These experiments were carried out to determine if the teleutospores 

 retain the power of germinating after wintering in the earth. To this 

 end, haulms of Agropyrum re pens Beau v. and leaves of Phragmites communis 

 were kept in pots, the plants having been attacked by Puccinia graminis 

 Pers. and P. Phragmitis respectively. The pots were partly filled with 

 sand and partly with garden earth, and were kept through the winter in 

 the open. Teleutospores were also kept in a pot without a covering of 

 soil for comparison. 



On March 30 the cultures of teleutospores were raised and dried. In 

 the control made about April 15 the teleutospores kept imder soil or sand 

 had germinated better than those kept in the air. The cultures raised 

 on April 30 germinated equally well (May 8). The pots were left in the 

 open until the end of April, then the}' were placed in the glass-house, hvX 

 without watering. On May 25 when other cultures were taken up, the 

 soil of the pot was still damp ; in P. graminis the power of germination 

 was good, in P. Phragmitis it had suffered a little. 



In conclusion, the teleutospores of " rust " in grasses, that have been 

 wintered in the earth, germinate in the following spring at least as well 

 as those that have been exposed to the air. From which it follows that, 

 in practice, the haulms of attacked cereals after wintering in the earth, 

 in the next spring can reinfect the host of the aecides though not the ce- 

 real itself. 



1127- Breeding Experiments with a View to Obtaining a Helianthus Resistant to 



" rust" {Puccinia Neiiant/li). — See number 1072 of this BuUdin. 



1 128 - Mildew of Cereals {Sclerospora macrospora) in Spain (i). — arropheles, 



in El iAtltiiador Modcrno, \'ol. \'I, No. 4, i lig. pp. 4, Barcelona, 1916. 



In the province of Huesca (Aragon), the wheat harvest of 1915 suffered 

 a loss of at least 40 per cent. This loss has been attributed to an attack 

 of " mildew ". 



The parasite has not so far been recorded on rice in Spain. 



RESISTANT 

 PLANTS. 



DISEASES 



OF VARIOUS 



OlOPS 



(i) See B. Oct. 191 5, No. iu()G and B. Dec. 191 5, No. 1346. 



(Ed.). 



