Salm o n , On Specialization of Parasitism in the Erysiphaceae. 291 



Zeit ihrer Eeife eine Anlage zur Sporenentwicklung- zu bemerken 

 ist, einige Tage im Wasser liegen (in nur feuchter Atmosphäre, oder 

 wenn dieselben auf dem Wasser schwammen, gelang mir der Ver- 

 such niemals), so zeigen sich schon am zweiten, resp. dritten Tage 

 bedeutende Veränderungen in dem vorher sehr gleichmässig fein- 

 körnigen Inhalt.' Wolff then describes the changes which take 

 place in the protoplasm of the asci, resulting in the formation of 

 8, or more rarely 4, ripe ascospores at the end of 5 or 6 days. 



In my experiments, dead or nearly dead leaves of Barley bearing 

 numerous perithecia contaniing asci fiUed merely with granulär proto- 

 plasm were well submerged in tap-water on Aug. 22. At the end 

 of 4 days the perithecia were examined, and were found to contain, 

 almost without exception, asci containing ascospores. The asco- 

 spores were either fully formed, in some cases being foimd escaped 

 fi'om the ascus on the perithecium being opened, or were in the 

 final processes of being developed in the ascus. Their number was 

 4, 6, or 8. Control examples at this date, as well as later, showed 

 no signs of the formation of ascospores. 



Similar leaves bearing perithecia on both sides were then floated 

 carefully on the surface of tap-water. At the end of 4 days the 

 fungus was examined. The perithecia borne on the under surface 

 of the leaf in contact with the water possessed asci containing 

 usually 8, but sometimes 4, or 6 spores. These ascospores were 

 fully formed, and were apparently ripe, as they were found frequently 

 to have escaped from the ascus on the perithecium being opened. 

 It was found, further, that the perithecia on the upper surface of 

 these leaves, exposed to the air and showüig no signs of having 

 been in contact with the water, possessed asci with either fully 

 formed ascospores, or ascospores in the last stages of development. 

 The air contained in the pannose mycelium of the fungus prevented 

 water being freely drawn up to the upper surface of the leaf, which 

 everywhere appeared quite dry. On blotting - paper being applied 

 to the upper surface and pressed firmly down it was, however, found 

 possible to draw up a little moisture from the wet lower surface of 

 the leaf. It was doubtless by means of such moisture drawn up, 

 as well as that obtainable from the surrounding atmosphere, which 

 was kept saturated with moisture during the experiment, that the 

 asci of these perithecia had been able to continue their growth and 

 produce ascospores. The experiment shows that, contrary to Wolff 's 

 Statement, ascospores can be produced not only in perithecia in 

 contact with water (without being submerged) but even in ones 

 simply absorbing moisture from a wet leaf or from the atmosphere. 



An experiment was undertaken in order to ascertain if the 

 deprivation of free oxygen — a factor which might have come into 

 Operation in the case where perithecia were submerged in water — 

 would induce the production of ascospores, A leaf of barley covered 

 with perithecia was placed in an open tube. This tube was placed 

 in a larger one wliich was fiUed to one-third with a very strong 

 Solution of pyrogalhc acid and potassium hydrate. The larger tube 

 was hermetically sealed with a caoutchouc stopper. The fungus in 

 the smaller open tube was thus exposed during the course of the 

 experiment to an atmosphere deprived of oxygen. At the end of 



