108 



ON THE PROPAGATION OF BUNT. 



parasitic fungi. My own opinion rests as it did at the time of 

 the publication of my former memoir ; certainly it has not been 

 made less strong by another year's experience. Be the degree 

 of uncertainty however on the subject what it may, I make no 

 apology for again adverting to it, especially as the observations 

 I have to record bear upon a question of much importance, and 

 which, in the hands of persons of more leisure and ability, may, 

 if followed out, increase our knowledge in several matters of 

 which we are at present ignorant. 



It has been known for many years that the principal diseases 

 of cereal plants, such as rust, bunt, mildew, &c, are of vegetable 

 origin. Unger attempted to overthrow this notion, and to prove 

 that they were mere exanthemata, analogous to eruptive diseases 

 in animals. The observations, however, of Corda, Leveille, and 

 others, have now completely established the fact, that the pro- 

 ductions in question are not mere modifications of the cellular 

 tissue, but that they spring from a distinct mycelium, and are 

 as certainly vegetable as any other fungi. It was long since 

 also ascertained by Bauer that one of them, viz., bunt, could be 

 propagated with certainty by rubbing the grains of wheat with 

 the spores, and the practice of steeping wheat previous to its 

 being sown, whether founded on more or less correct notions of 

 the nature of the disease, a practice seldom neglected with im- 

 punity, is in accordance with his experiments. As regards the 

 mode of propagation of these diseases the most vague and ill- 

 founded notions have prevailed, the more general opinion being 

 that the reproductive organs themselves were absorbed by the 

 spongy tissue of the roots, or by the stomata, and so traversed 

 every portion of the plant by means of the intercellular passages, 

 or rooted in the tissue at the base of the stomata. It has 

 not in general been understood that those bodies which, as far 

 as has been observed, are the only ones destined to produce 

 mycelium, are far larger than the intercellular passages, and 

 frequently than the individual cells, or even the stomata them- 

 selves. The figure given by Bauer of the contents of the spores 

 of Puccinia graminis is not correct, as may be ascertained by 

 actual examination, or by comparison of Corda's admirable 

 figure. The spores, in point of fact, contain merely a grumous 

 mass, with one or more oil globules, and by no means distinct 

 sporules, as supposed by Bauer. 



Now, whatever may be the cause of the disease in potato 

 tubers, I look upon it as matter of absolute certainty that the 

 destruction of the aerial portion of the plant is due to the 

 developement of Botrytis infestans. The notion that it is a 

 mere consequence of a previously diseased condition is, I firmly 

 believe, quite untenable. It becomes then matter of interest to 



