3710 



des FrutihtlQibtens ist ausgeschossen", according to him. 



gerlod of incubation 



The time y/hich elapses between infection of the heads and 

 the first appearance of "honey dew'* which is the first positive evidence 

 that infection has taken place, varies considerablsr V7ith environmental 

 conditions, also with the stage of flov/ering of the host. Dry and cold 

 weather is lilcely to retard the appes.ran.ce of the honey dew, while moist 

 and hot weather as is well Icnown vdll hasten and favor an. abtrndant secretion 

 of the honey dew. In plants infected before anthesis, first signs of in- 

 fection appear later than under other conditions. 



The period of incubation varies also vath different species 

 of Claviceps, For C'S purpurea it is from seven to fourteen days; in cold 

 weather, usually about fourteen days. For Claviceps on Poa it is only five 



to sijt days; C» mlsoni,oi--?j;.t to thirteen days; Claviceps on Lolium eight 



[ • — ^— — >■ 



C. BiicrocephAl* 

 to eleven days; d, m±gr aa sagfec^ , ten to sixteen days. While these periods 



give an idea of the relative length of the incubation period, they should 

 not be taken at their face value, because all of these data have been 

 secured at different times under different conditions. It seems likely 

 that if inoculations had been made at the same tire and under the same con- 

 ditions with various Claviceps species and biologic races the results 

 might have been more similar. 



Time of natural infection 

 Infection is nature, as well as under artificial conditions 

 takes place usually dxxring the flowering period of the host. There is still, 

 however, some difference of opinion as to the particular stage of blossoming 

 during T,itiich the plant is most sisceptible to infection. Engelke (62) foand 

 that infection with conidia was successful only before the flower was 

 pollenated, that is, previous to the production of the pollen tube by the 



