INFECTION-POWERS OF ASCOSPORES IN ERYSIPHACER. 161 
peemmasebh: elles, ce qui est moins probable, ks VEr ysiphe Graminis 
ndre son aire de dispersion sur d’autres hétes ?” 
ake giving the results of my experiments with the ascospores 
of LE. Graminis, a few remarks may be made on the metho 
ployed of obtaining the ripe ascospores, and of inoculating the 
plants. The material used was collected at Cambridge last 
August, and consisted of oat et of barley bearing peri- 
thecia. The leaves were kep t dry in @ box during the winter 
months. Asis well known, the asci of H. Graminis in the autumn 
filter-paper, ae water howe added to produce a film over the 
surface. Under these conditions, i in a temperature of about 18°, the 
protoplasm of the ascus at once resumes its activity, and med 
take place which result in the formation of four, six, or eight asco 
ores. The whole process is completed in three to five, usually 
four, days, by which time ripe ascospores are produced. Two 
teresting facts were observed at the time of the maturity of the as a 
viz. the regular dehiscence of the perithecium and the ejection of 
the ascospores. It was found that the perithecium spontaneously 
opened ; the ascospores were forcibly ejected into the air, and were 
found germinating in the drops of water condenses on the cover of 
the Petri dish, at a distance of 2 cm. from the perithecium. The 
peecsunent was repeated again and again, with invariably the same 
esult. e process of this dehiscence and the ejection of the 
— ae was closely followed, and the following details observed. 
Numerous leaves Doaiee perengo were poet on ” filter-paper, 
as described above, on the bottom of a ri dish ; on the fourth 
ay a few of the "oeetieae had pee opene od! and asco- 
spores had been thrown up to the “oP a the Resn dish, where they 
had commenced gereinabns On t many aupareds of 
spores were thus thrown up, and by the sixth aay al ops 
water condensed on the cover were sown Wi ousands Mot asco- 
spores. The spores were often found in little groups, suggesting 
that they had been ejected all together from the ascus, as 1s the 
in Ascobolus, &. The dry “perithecium of Graminis is 
usually concavo-convex, but on aa moisture it beco bi- 
Journat or Borany.—Vor. 41. [May, 1903.) M 
* 
