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Journal of Agricultural Research voi. xxn. no. 3 



confirmed by the control plants which remained free from mosaic mottling 

 after aphids taken from healthy plants had fed upon them. The results 

 secured from inoculation with aphids are presented in Table II. 



Table II. — Transmission of mosaic of m,ustard, pe-tsai, and turnip by means of aphids 



« Date of last observation, Apr. 2, 1920 and 1921. 



From the data indicated in Table II it is evident that aphids transmit 

 mosiac of the crucifers in question between different species as well as 

 among plants of the same species, as was suggested in Table I on juice 

 inoculations by means of rubbing. It will also be noted that the period 

 in which the first mosaic mottling appeared corresponds very closely to 

 that obtaining with mosiac diseases of other plants. As with the plants 

 inoculated by rubbing, the plants inoculated by means of aphids devel- 

 oped the mosaic symptoms only on the younger leaves. Mosaic symp- 

 toms on the inoculated plants were like those which were observed on 

 mosaic lots taken from the field. 



Since turnips from mosaic plants taken from the field continued to 

 produce mosaic foliage it is apparent that such plants become a source 

 of infection if planted near susceptible varieties. Mustard seed from 

 mosaic mustard plants apparently develop healthy seedlings. This was 

 observed in loo seedlings, which were grown from seed from mosaic 

 mustard in the fall of 1920; in this test every seedling was free from 

 mosaic mottling. 



