ASCOMYCETES 201 



X. STEM ROT OF CLOVER 



Schrotinia Trifoliorum Eriks. 



Chester, F. D. Rot of the Scarlet Clover. Del. Agl. Exp. Sta. Rept. 3 : 



84-88. 1890. 

 Eriksson, J. Bot. Centrbl. 1 : 296. 



This fungus is occasionally very destructive to various species 

 of clover (Trifolium) in Europe, and it has several times been 

 reported as epidemic in the United States. In this country, how- 

 ever, it is not so widely distributed or so constant in its injurious 

 effects as to have been often observed. The effect of this fungus 

 upon the host is to produce a decay near the base of the stool, or 

 practically at the surface of the ground, as the result of which the 

 plant wilts. The mycelium, which is from the beginning evident 

 on the surface, invades the tissues and ordinarily by the time that 

 the plant is killed numerous small, black sclerotia are produced 

 upon the surface of the affected parts. The sclerotia vary in size 

 from 1 to 5 or 6 mm. in diameter. Sown upon moist sand or 

 wintered upon the decaying remains of the host there are pro- 

 duced the following spring the brown apothecia characteristic of 

 this species. The asci are long cylindrical, about 180 x 12 p. 

 Ascospores, which are disseminated in the early spring, lose 

 their power of germination upon being dried, and it would seem, 

 therefore, that they must penetrate the host at this time. It is 

 claimed, on the other hand, that the sclerotia may retain their 

 vitality for a period of several years if the conditions are un- 

 favorable for germination. Some regard this fungus as identical 

 with Sclerotinia Libertiana. 



Sclerotinia Betulae Wor. 1 This birch catkin disease is common 

 in birch forests of Russia. Sclerotia, so far as is known, are pro- 

 duced during the development of the catkins, falling and remain- 

 ing on the ground over winter. The apothecia are formed the 

 following spring, each sclerotium producing several small apo- 

 thecia of light color. The fungus has also been found in Europe, 

 Asia, and America. 



Sclerotinia tuberosa (Hedw.) Fckl. develops enormous sclerotia 

 on the rhizomes of Anemone nemorosa. 



1 Tubeuf. Diseases of Plants, /. c, 261. 



