M. C. COOKE ON BDNT SPORES. 169 



being in all cases very obtuse, and many times larger than the 

 intercellular cavities of the tissue of the roots. 



"The parasite, meanwhile, had undergone a very curious change, 

 the spores being no longer separate, but connected with one another 

 by one or more short transverse tubes, exactly as in the threads of 

 Zijgnema. 



"Two days later many more of the bunt spores were ruptured, 

 and' the mycelium more elongated ; and after three more days the 

 parasite was vanishing, and scarcely visible any more en masse to 

 the naked eye, while the mycelium had increased to the length of 

 six or more diameters of the spores. The young infected wheat 

 plants were now evidently diseased, the sheaths and base of the 

 leaves looking crumpled, and spotted either with white or brownish 

 specks, and the whole appearance less healthy than that of the un- 

 impregnated plants. 



" The diseased sheaths were now, in most cases, full of mycelium, 

 but no such appearance was visible in the healthy state. Though 

 the disease had evidently commenced, it is to be observed that the 

 tubes protruded by the spores were but slightly developed, and that 

 though the utmost paius were taken, I coiild trace no connection 

 whatever between these and the diseased tissue. 



" In a single instance only, ten days after the first appearance 

 of disease, in examining some little white specks which appeared 

 on the leaves of the bunted wheat, I saw a curved filament passing 

 through one of the stomata, but whether from the outside to the 

 inside, or the contrary, I cannot say. The mycelium in these white 

 specks was not abundant, but thicker than the walls of the cells. 



" In a month from the sowing of the wheat, the fecula of the 

 grains being then nearly absorbed, it was difficult to find any spores, 

 and no further development of mycelium directly from the spores 

 had taken place. 



" The first bunted ear appeared four months from the time of 

 sowing, and while every impregnated plant produced bunted ears, 

 not a bunted grain appeared on the plants which sprang from un- 

 infected seed. 



" The production of the parasite on the spores of bunt was con- 

 stant in my experiments, and was repeated at Bristol and Clifton 

 under the eyes of Mr. Thwaites and Mr. Broome, to whom I had 

 communicated bunted grains of wheat. I was at first inclined to 

 think that it had something to do with the reproduction of the bunt, 



L 2 



