George Raymond Gage 7 



Lutman (1910:1200-1206), who produced artificial inoculation by 

 spreading cultures of sporidia on young seedlings, emphasizes the fact 

 that haustoria are absent, the pathogene being entirely intercellular. 

 His description of spore formation is similar to that given above for II. 

 an nat . 



EPIPHYTOLOGY 



Environmental factors governing both loose and covered smut have 

 been assumed to be more or less alike. 



Tt mpt raturt 



Low temperatures of the soil are held to favor both pathogenes. 

 Spores germinate readily at temperatures as low as 10° C. At such a 

 temperature oats germinate very slowly. Thus the pathogenes are able 

 to penetrate and reach the growing point of the suscept before it 

 emerges from the soil. If temperatures of 15° or above obtain, then the 

 suscept grows so rapidly that the pathogene has little chance to become 

 established in the tissues of the growing point. This idea was advanced 

 by Brefeld (1895: 25), who, in all of his inoculation experiments, after 

 spraying the young seedlings with sporidia kept them at a temperature 

 of 10° for a period of several days before planting. Clinton (1900 : 305) 

 showed by experiment that late planting of oats reduces infection. Lut- 

 man (1910:1201), working with U. levis, obtained infected plants by 

 smearing sporidia on the young leaf sheath and keeping the inoculated 

 seedlings at a temperature of 12° for from five to seven days. Heald 

 (1919: 31), however, is of the opinion that late seedings produce more 

 infection. Butler (1918: 180) also takes an opposing view with respect 

 to temperature. He says, "When the temperature at sowing time is low, 

 oats are more likely to escape smut, since the spores require a considera- 

 bly higher temperature for germinating than the oat grains themselves." 

 Tubeuf (1897:286-287) clearly has misinterpreted Brefeld when he 

 says Brefeld "found that oat-smut germinated best at 10° C, and not 

 so well above 15° C." Brefeld did not find that the smut spores germi- 

 nated best at 10° and not so well above 15°, but that effective penetration 

 took place better at 10°. 



On the one hand, then, Brefeld, Clinton, and Lutman believe that low 

 temperatures favor infection, while Heald and Butler seem to think that 

 high temperatures are favorable. 



Moisture 



Moisture relations may be particularly influential at two different pe- 

 riods in the life history of tin- pathogene— al tin- time of spore dissemi- 

 nation, and at the time of spore germination. It is obvious that a suffi- 



