280 SUMMARY OF CURRENT RESEARCHES RELATING TO 



given off, was the facility with which they floated in the air, having 

 little or no tendency to subside. Their specific gravity must be very 

 low, and this, aided by their gyrations, will account for the extensive 

 and, when aided by air-currents, rapid diffusion of Elvellaceous 

 sporidia. 



Formation and Germination of the Spores of TJrocystis.* — 

 E. Prillieux has succeeded in following out the mode of germination 

 and the process of formation of the spores in two species of TJrocystis, 

 U. Violce and Colchici. 



In all the species of TJrocystis the spores are associated into ovoid 

 or roundish masses, the outside portion of which is formed of cells which 

 must be regarded as imperfect and sterile spores, while a small 

 number of fertile spores occupy the centre of the mass ; those are 

 dark brown and nearly opaque, while the outer ones are transparent, 

 and but slightly coloured. In TJ. Violce the number of fertile spores in 

 each mass varies from two to eight, while occasionally there is only 

 one ; in TJ. ColcMci there are usually only one or two. In both species 

 the mass of spores is surrounded by a close tissue of filaments, in the 

 midst of which the masses may be observed in various stages of develop- 

 ment. These filaments penetrate the interior of the cells of the host, 

 while those of the vegetative mycelium develop exclusively in the 

 intercellular spaces. They are the final ramifications of the mycelium, 

 and are well termed the sporogenous filaments. From its origin the 

 glomerulus or mass of spores is seen to be composed of interwoven 

 sporogenous filaments, forming a little ball which recalls the structure 

 of some sclerotia. As this glomerulus increases in size, certain of its 

 central cells become distinguished by their greater size, and assume 

 the character of true spores, while the adjacent ones develop into the 

 superficial sterile spores, and the rest of the sporogenous filament 

 becomes mucilaginous, and finally disappears. The fertile spores are 

 in fact formed from the extremities of the sporogenous filaments in the 

 same way as in Tilletia rather than in TJstilago. 



The germination of the spores of TJrocystis Violce takes place in the 

 following way. Three or four days after having been sown on water, 

 the spore gives birth to a promycelium which may be longer or shorter, 

 unicellular or multicellular. At its extremity the promycelium pro- 

 duces a crown of six sporidia. Each glomerulus usually produces 

 only one promycelium, though occasionally there are two or three. 

 The sporidia are at first short and somewhat curved like a finger ; 

 ultimately they elongate, all the protoplasm of the promycelium 

 passing into them. They germinate while attached to the apex of the 

 promycelium. Each produces at its extremity a secondary sporidium, 

 twice as long as but narrower than the primary sporidium. The 

 protoplasm finally passes from the primary into the secondary sporidia, 

 which then detach themselves and float on the surface of the fluid. 

 The process of germination therefore differs from that previously 

 described by Kiihn and Wolf in the case of TJ. occulta. 



* Ann. Sci. Nat., x. (18S0) pp. 49-61 ; and Bull. Soc. Bot. France, xxvii. 

 (1880) pp. 204-8. 



