44 



A Clover Fungus. 



elliptical, and when released from the asci may be carried by 

 the wind or other agencies to clover plants far and near. 

 Rehm describes the germination of the ascospores, and gives 

 figures illustrating it in the work already cited. He shows 

 in this interesting account that the ascospores, placed in 

 water or in air saturated with moisture, swell and emit germ- 

 tubes in four to six hours, which grow rapidly, and in 

 t\7enty-four hours attain the length of the ascospores, and 

 then begin to ramify. In some circumstances the branches 

 develop very small globular sporidia at their extremities, 

 occasionally isolated, but generally in files of four to eight. 

 The germination of these sporidia has not been observed, 

 but in all probability they also germinate in suitable con- 

 ditions. In water containing proper nutritive elements 

 the germ tubes from the ascospores form filaments of 

 mycelium, and occasionally in the same cultures it is found 

 that certain of the ascospores yield mycelium while others 

 produce sporidia. Rehm succeeded in artificially infecting 

 clover plants under glass, in a humid atmosphere, with Sclero- 

 tmia trifoUorum^ by placing the apothecia upon their leaves. 

 In six to eight days mycelium was formed within the leaves ; 

 the plants finally succumbed, and sclerotia were found at the 

 crowns of the roots. Moisture is necessary for the germina- 

 tion of these spores. De Bary says : " It is estimated that at 

 least 95 per cent, of the ripe ejected spores of Sclerotinia 

 ciboi'ioides lose their power of germination if they are kept dry 

 in the air on glass plates for twelve days in a temperature of 

 about 20 degrees C* 



According to Frank the sclerotia of Sclerotinia trtfolioritm 

 are able to remain in a dry state for two and a-half years with - 

 out losing their power of germination. f This adds most 

 materially to the chances of infection by this fungus, and indi- 

 cates that it is essential for clover growers to avoid taking 

 clover, sainfoin, and lucerne crops for long periods in or near 

 fields where infection has occurred, as well as to modify the 

 practice of letting clover leys remain down for two or more 



* The Comparative Morphology and Biology of The Fungi Mycetozoa and Bacteria. 

 By A. De Bary ; translated by Garnsey and Balfour. 1887. 



t Die Pilzparasitaren Krankheiten der Pflanzen. Dr. A. B. Frank. 1896. 



