146 SCIENCE PROGRESS 



Biologically, however, in two essential points the differences 

 are marked. The smut spores of barley and of wheat do not 

 retain their vitality long — beyond some twelve months — i.e. 

 probably not into the second year after their formation. The 

 oat smut spores, on the contrary, are capable of sprouting for 

 several years after their production. Further, in a nutritive 

 medium, the oat smut spores sprout, and form the jointed pro- 

 mycelium or hemi-basidium, the segmented members of which 

 give rise to conidia. These conidia go on forming endlessly 

 as long as the food material lasts, budding and forming yeast- 

 like conidia. These conidia finally send out the penetrating 

 hyphae. In wheat and barley smuts this abundant conidial 

 formation does not occur. Manured soil is then the most 

 suitable medium oat smut spores could have for their almost 

 interminable proliferation. Artificial infection of the healthy 

 oat plant in flower, and of oat grains sprouting, shows that, 

 while in nature infection of the flower from smutted oat panicles 

 by the help of the wind may happen, the main source of infection 

 is from the spores left in the soil or clinging to the sown 

 seed. Hence in cultivation, treatment of oat seed with a fungi- 

 cide and appropriate rotation of crops are the proper steps to 

 take to ensure the crop against smut. 



These interesting and important results of the investigation 

 of the mode of infection of the wind-pollinated grasses led 

 naturally to a re-examination of cases of certain insect-pollinated 

 flowering plants showing smut in their flowers. The Caryo- 

 phyllacece or Chickweed order — many with white night-opening 

 flowers — furnish convenient examples, and one of those, 

 Melandrmm album} was specially selected by Brefeld for experi- 

 ment. Though the experiments were not carried out on a 

 very large scale, and suffered from various disturbances, the 

 general results show that the sticky smut spores are carried 

 by insects from the diseased anther to the stigma of the female 

 flower, that the spores sprout in the stigmatic juice, and finally 

 infect the ovules. The seeds planted next year give smutty 

 plants. Here too we have infection of flower from smutty 

 flower, and smut spores living saprophytically. The chief 

 difference from barley and wheat is that the smut spores are 

 conveyed with the pollen grains from one flower to another 

 by insects, not, as in these grasses, by the wind. A third 



1 Lychnis alba, Mill. 



