70 James G. Horsfall 



spaces are reduced somewhat by the muriform cell arrangement. In 

 crimson and red clovers the contents of severely infected cells tend to 

 disorganize." 



Etiology 



Since the causal agents of mosaic diseases remain obscure, a discussion 

 of this feature of clover mosaic does not come within the scope of this 

 paper. 



Whatever the nature of the causal agent of clover mosaic, pathogenic 

 effects certainly are produced and the agency is transferable from one 

 clover plant to another. McLarty (1920:503) obtained infection with 

 juice from diseased plants by inoculating it into healthy leaves both 

 before and after passing it through a Chamberland filter. Dickson 

 (1922 a: 42) transmitted the disease by means of aphids. 



Dickson and McKostie (1922:42) conclude from their experiments 

 on planting seed from diseased red-clover plants that the malady is seed 

 borne and impairs the germination. Seedlings from infected seed or 

 overwintered infected plants serve as sources of primary inoculum. The 

 agents of inoculation in nature are various sucking insects, among which 

 the aphid Macrosiphum pisi Kalt. has been shown to be responsible (Dick- 

 son and McRostie, 1922:42). Elliott (1921:147) showed that symptoms 

 appear within from ten to fifteen days after inoculation. 



According to Johnson (1922), " clover mosaic is seemingly favored by 

 low temperatures." 



Control 



But little can be offered yet in the way of control. Selection of seed 

 from disease-free fields should be of some value, but obviously roguing 

 diseased plants as practiced for other mosaic diseases is impractical 

 under present conditions of clover-seed production. 



KABATIELLA ANTHRACNOSE OF CLOVER 



Except for observations on distribution and severity of the disease, 

 the writer has made but little study of Kabatiella anthracnose of clover. 

 The malady frequently is of grave importance in the State. The Col- 

 letotrichum anthracnose has been reported from New York but was never 

 collected by the writer. 



Suscepts 



Red clover only is commonly affected by this disease in New York. 

 The following plants have been reported elsewhere as suscepts: Trifolium 

 purpureum, T. medium (Malkoff, 1902:283); T. hybridum (Fulton, 1910: 

 752), T. suaveolens, T. repens (Stapledon and others, 1922:87); T. in- 



