232 RESEARCHES ON FUNGI 



thousands of asci at the moment when a discomj'cetous fruit-body 

 puffs either in the field or in the laboratory is simpler than the one 

 suggested by myself in 1909 and is in good accord with his experi- 

 mental observations. I am therefore inclined to accept it. How- 

 ever, that another factor, in addition to that of purely physical 

 strains in the ascus wall, may have something to do with the bursting 

 of an ascus seems to be shown by the ah-eady recorded results of my 

 experiments on hymenia of Aleuria vesiculosa submerged in water. 

 We can scarcely suppose that non-poisonous substances (sodium 

 chloride, potassium nitrate, grape sugar, and glycerine) do not set 

 up strains in the ascus wall whereas poisonous substances (iodine, 

 mercuric chloride, silver nitrate, copper sulphate, sulphuric acid, 

 and alcohol) do. The fact that poisonous substances cause sub- 

 merged asci to burst, whereas non-poisonous substances do not, 

 seems best explained by assuming that poisonous substances stimu- 

 late the protoplasm at the end of each ascus to act upon the ascus 

 wall in such a way as to cause the operculum to open outwards and 

 that non-poisonous substances do not so stimulate the protoplasm. 



In recent years Richard Falck ^ has studied the conditions which 

 affect the puffing of Discomycetes and permit of the spores escaping 

 from the fruit-bodies ; and, as a result of his investigations, he has 

 divided the fruit-bodies of Discomycetes into two groups : (1) the 

 radiosensitive, i.e. those which emit spores when warmed by radiant 

 heat given out by a lamp or the sun, etc., e.g. Morchellaceae, Gyro- 

 mitra, and Verpa. and (2) the tactiosensitive, i.e. those which puff 

 when touched or blown upon, e.g. Aleuria, Galactinia, Otidea, 

 Peziza, and Pustularia. 



Puffing illustrated by Photography. — The spore-cloud which, 

 at the moment of puffing, is emitted from the fruit-body of one of 

 the larger Discomycetes, is made up of tens of thousands or even 

 millions of spores and can readily be seen A\ith the naked eye. 

 Dickson and Fisher,- working with Sclerotinia sclerotiorum ( = S, 



1 R. Falek, " Ueber die Sporenverbrcitung bei don Asoomyceten. I. Die radio- 

 sensiblen Discomycctcn," Mycologische Untersuchungen iind Berichte von R. Falck, 

 Jena, Bd. I, Heft II, lOK),])}). 77-144 ; " Ueber die Sporenverbreitung bei den Asoo- 

 myceten. II. Die taktiosensiblcn Discomyceten," ibid.. Heft III, 1923, pp. 370^03. 



2 L. F. Dickson and W. R. Fisher, " A Method of Photographing Spore Dis- 

 charge from Apothecia," Phytopathology, Vol. XIII, 1923, pp. 30-32. 



