THE INFLUENCE OF THE MYCELIUM OF USTILAGO VIOLACEA. 117 



affecting our cereals, excepting bunt (Tilletia tritici), is not by any 

 means absolutely known even yet. From the remarkable dis- 

 coveries of Brefeld, that they can exist for long periods outside 

 living plants, it seemed as if the problem had been definitely solved. 

 There are, however, still remaining certain points to be cleared 

 up. For instance, Brefeld found that when the spores of Ustilago 

 segetum were placed in a sterilised decoction of herbivorous 

 excreta, they formed yeast-colonies, and continued to reproduce 

 themselves by budding like yeast cells until the nutrient fluid 

 was exhausted. He therefore concluded that it was from the farm- 

 yard manure that the cereal crops became infected. At the time 

 his observations were first published, being much interested in 

 the subject, I made careful inquiries amongst the farmers of West 

 Norfolk as to whether their crops were not much more injured by 

 smut when they were fertilised with farmyard manure than when 

 artificial manure was employed. I also examined a number of 

 fields myself with this point in view. But as far as I could see r 

 and as far as I could learn, there was as much smut after artificial 

 as after farmyard manure. 



Then, again, the exact contour of a large manure-heap in a 

 field can be readily enough made out by the luxuriance of the 

 growing crop as compared with the rest of the field ; but, con 

 trary to what one would have anticipated from Brefeld's observa- 

 tions, smutted ears are not more common on the site of the 

 manure-heap than elsewhere in the field. Perhaps some member 

 of the Scientific Committee better conversant with Brefeld's more 

 recent writings than I am may be able to clear up these points. I 

 have elsewhere stated in detail my non-success of infecting cereals 

 with smut (Ured. and Ust. p. 101). 



NOTES ON HOAR FROST. 



By Mr. C. B. Plowkight, F.R.H.S., F.L.S. 



Injuries to Trees by Hoar Frost.— The remarkable hoar- 

 frosts, which excited so much admiration on the part of all those 

 who were fortunate enough to see them, in the early part of 

 January 1889, have produced results in this district such as the 

 present generation has not before witnessed. 



