20 Journal of Agricultural Research vol. xx. no. i 



F. herbarum (F. metachroum) (13), F. didymium, F. avenaceum (F. subu- 

 latum), and F. lolii. He showed also that F. nivale causes not only the 

 snowmold but also rotting of the roots and killing of the young cereal 

 seedlings. Later it causes footrot of the grown plants, usually following 

 the wounding of the plants by insects or other agencies. F. nivale 

 attacks the heads of the cereals during the period beginning at blossom- 

 ing time and extending to the ripening of the crops and causes blighting. 

 In this connection he distinguished between primary infection, which 

 takes place before the ripening of the plants, and secondary infection, 

 during the period of maturity and harvest. In the secondary infection 

 he found that not only F. nivale but also less parasitic Fusarium species 

 play an important r61e. 



Naumov (5), studying the cause of cereal headblighting, which is 

 reported to be severe throughout Russia, found that Gibber ella saubinetii 

 and Fusarium avenaceum (F. subulatum) are the cause of this disease in 

 Russia and Siberia, the first being common in the southern and the 

 second in the northern part of the country. 



Studying the pathogenicity of these organisms, Naumov reported 

 that: 



(1) Infection of the soil will result in the blighting of heads of wheat 

 and barley. How the organisms introduced into the soil under sterile 

 conditions reach the heads of the plants where they cause blighting is 

 not quite clear. Throughout the paper Naumov states that the myce- 

 lium of these Fusarium species is found in all parts of the plants, but it 

 is not very clear whether infection in the roots and the lower parts of 

 the plant proceeds up the stem, becoming systemic, or whether the 

 various parts are infected separately by external infections. Though 

 this view is not directly and plainly stated, in many cases the reader 

 will be led to believe that Naumov considers the infection systemic 

 and that it proceeds from the roots up to the heads, since in many places 

 in this paper he speaks of finding the mycelium of these organisms in 

 all the tissues of roots, stems, heads, leaves, and sheaths, but nowhere 

 causing any anatomical changes. 



(2) Spores or conidia of the causal organisms when on the seed, or nat- 

 urally infected seed, can cause blighting of the seedlings. 



(3) Conidia, ascospores, and mycelium of the organisms, when placed 

 on normal young plants, with or without wounding, cause infection. 



(4) Spraying the heads of wheat, rye, and oats with a water suspen- 

 sion of conidia of these organisms produced typical blighting of the 

 infected heads as observed in nature. 



(5) The results given under (4) were also obtained with ascospores of 

 Gibberella saubinetii. 



(6) These organisms can invade the tissues of the seed, straw, and 

 heads of the cereal crops after ripening and harvesting if conditions are 

 favorable. 



