'20 A SCLEROTIAL DISEASE OF RICE. 



some unusual structures in the sclerotiuin. He states, that 

 when the sclerotia are about a f'ortnij^ht old several vacuoles 

 make their appearance in the interior, and, ultimately, coalesce 

 to form one large central space ; the sclerotium thus becomes 

 hollow. From the solid exterior hyphic now grow into the 

 central vacuole and bear spores. The spores are circular 

 structures, about l-//- in diameter, and are cither borne termin- 

 ally, or else laterally, on the walls of the hyphic. Such a 

 method of spore formation was never observed in our cultures, 

 nor did a series of microtomed sections reveal a sclerotium as 

 anything but a solid pseudoparenchymatous structure. The only 

 bodies bearing any resemblance to the spores of Cattaneo were 

 the oil drops in the hyphye. By crashing a sclerotium the 

 hyphcC become torn and the oil drops set free. Under these 

 circumstances the oil drops may adhere to the sides and ends 

 of hyphic, in positions not unlike those which Cattaneo figures 

 for the spores. 



No trac3 of a perfect stage was ever observed. Brefeld (1) 

 has pointed out that the sclerotia of certain Basidiomyceles 

 [Afjaricus, Cojrrimis, Typhula), and of Penicillium and Eryaiphc, 

 arise by the interlacing of branches of a single hypha, while those 

 of the genus Pcziza are formed rather from a plexus of inter- 

 woven filaments. This conjparison has been somewhat erroneous- 

 ly generalised by some writers (Stout 10) into the statement that 

 the sclerotia of Ikcsidiomycetes arise from a single h3^pha and 

 those of Ascornyceles from a plexus of hxqjhjc. In the genus 

 Ixhizoctonia it has been found (Shaw 8) that J\/ii:octonia Solani, 

 Kiihn, forms its sclerotia from a single hypha, whereas, in the 

 macro sclerotial species, of which Corticium vafjum is the perfect 

 stage, the sclerotia arise from a mycelial plexus. It is evident, 

 therefore, that this character does not atlbrd any basis for 

 taxonomic consideration, since both methods of sclerotial forma- 

 tion occur in both /ia.sidiomyccfcs and Ascomycctcs. 



It is interesting to note the changes in the appearance of the 

 fungus, according to the nature of the nutrient substtatum. 

 These changes arc most marked ill the colour and form of the 



