ON THE ANGUILLULID^. 87 



ratlier tlian vital, and due to the rapid imbibition of water by the previously dried 

 animal. 



With respect to the Vibrio tritlci, I may state that this year I succeeded in infecting 

 some wheat with young specimens taken from a gall several years old. As my stock was 

 small, the method followed was that adopted by Bauer — that is to say, the placing some of 

 the young Nematodes within the cleft of the seed, allowing them to dry in this situation, 

 and tben consigning the seeds to the earth in the ordinary way. This was done in the 

 end of Tebruary last, when eighty seeds so infected were sown in a box containing 

 ordinary soil ; and on the 8th of July I discovered one plant evidently diseased. It was 

 extremely stunted, being only about five inches in height ; and the whole specimen was 

 dry and withered, with the exception of the small and abortive ear. This contained no 

 healthy florets, the diseased ones being about fourteen in number, each being composed 

 of the sKghtly altered glumes and palea3 surrounding a gall of the usual size and ovoidal 

 shape, instead of a germen. In confirmation of this view of the gall-like nature of the 

 growth, as ascertained by Davaine', I may state that at the time when these bodies had 

 attained their full size and maturity, the other healthy plants Avere only just flowering, 

 the germens in them being minute and undeveloped. I am also able to testify to the 

 probability of the correctness of Davaine's description of the precise method in which the 

 disease is produced, and the young worms come in contact with the growing flower. 

 Before his time the only o1)servers who had attempted to explain the manner in which 

 the young Vibrios reacli the ear were Roffredi'^ and Bauer; and both these investi- 

 gators imagined the little Nematodes obtained an entry to the vessels of the plant, and 

 were so transmitted to the germen. Bauer, indeed, whose paper, apart from the special 

 subject on which he wrote — namely, the degree of vitality of these animals — is full of 

 inaccuracies, and whose figure and description of the adult animal is utterly unlike the 

 original, imagined that the young, found in what he considered to be the diseased grain, 

 were the products of a third generation in this spot, the two others having taken place 

 witliin the vessels of the stem of the plant during the progress of the animals towards the 

 flower. But the real process, according to Davaine, seems to be this : — When the infected 

 galls are sown together with. healthy seeds^ the young in a week or so, according to the- 

 degree of moisture of the soil, make their way out of the softened gall, and, diffusing 

 themselves in all directions, some come at last into contact with the budding plant just 



' Davaine has occasionally found a small abortive germen within the same floral envelopes with the gall ; and in 

 this case the gall is most likely to have been produced in one of the rudimentary scales, which would have gone to 

 form a stamen. He believes it may be formed out of any of the scales belonging to the central parts of the flower ; 

 and although, as a rule, all these parts participate in the formation of a single central gall, still occasionally as many 

 as three growths of this Icind develope within the same pair of glumella. On one occasion he found a growth of a 

 similar nature, and with the same kind of contents, growing from one of the leaves of the wheat. After this, addi- 

 tional proof as to the nature of the growth is almost superfluous. All interested in this remarkable disease of wheat 

 should consult M. Davaine's admirable memoir on the subject. 



" Observations sur la Physique, t. v. p. 1, 1/75. 



^ That the disease may be produced artificially, by placing the young within the cleft of a healthy seed, after the 

 method of Bauer, I can have little doubt, after the result of my own experiment, though Davaine seems to be rather 

 incredulous concerning this mode of its production {loe. cit. p. 16). 



