( 52 ) 



of varviiiiï shape and size, soluble in diluted hydrochloric acid in 

 \Yhich they left a structureless residue, soon appeared to I)elong to 

 the class of "calcospherites" : organic compounds of calcium treated 

 by the late Professor P. Harting in 1872 in a (piarto Treatise of the 

 Royal Academy of Sciences, entitled : "Morphologie Synthétique sur 

 la production artificielle de quelques formations calcaires organiques". 

 There could be no doubt that these calcospherites stood in no 

 relation to the fungus, luit had been produced by the gelatine, while 

 on the other hand, the presence of conidia proved that the new 

 Sckrotinia, like other species of the same genus, could multiply by 

 conidia as well as by ascospores. 



On the maltgelatine-plates which had been exposed to the air of 

 the tobaccoflelds and in the drying-sheds, the same mouldy spots 

 developed under the most favourable conditions of the laboratory, 

 whicii had drawn our attention on the stems and leaves in the tields, 

 and wJiich had afterwards been artificially nudtii)lied. More important 

 still is that somewhat later the same sort of Sclerotia developed, the 

 germination and further development of which gave origin to the 

 formation of apothecia. 



There cannot he the least doubt that the conidia floating in the 

 air, by settling on the gelatine-plates, had produced the infection and 

 the ensuing phenomena, so that these last experiments throw a clear 

 light on the i)0ssibility of extensive tobaccofields being ruined in a 

 very short time, as soon as by a pi-evailing uncommonly damp con- 

 dition of the atmosphere a small patch of mould has anywhere 

 found occasion to de^■elop ihi'eads. At the same time they show that 

 the opinion of von Tavel (Vergl. Morph. der Pilze, 1892, p. 105): 

 "Es (die Arten von Sclerotinia) sind parasitische Pilze, deren Sclerotien 

 im Innern der Pflanzentheile sich bilden ganz nach Art einer Ciariceps' 

 cannot be admitted for Sclerotinia JVicoticmae, and that here an 

 ectogenous formation of the Sclerotium has been substituted for an 

 endogenous one. 



III. CULT1VATI0N-EXPF,RIMENTS APPLIED TO SCLEROTIUM NICOTIANAE. 



The sclerotia whose development it was desired to study were 

 buried in sand, garden-soil, forest-soil and leaf-earth respecti\'ely, 

 placed in suitable dishes partly in daylight, partly in dark, and after 

 having been properly ^vatered exposed to various temperatures among 

 which that of 22° C. Not earlier than 6 weeks later the first sign 

 of new life was observed in the shape of numerous black-brown 



