ia4 LEIPNER, ON SILICA IN PLANTS. 



ergot is a body unconnected with the OA^ules of the grass^ 

 taking its rise at tlie bottom of the cavity of the spermato- 

 gonium of the Sphacelia or fungoid groAvth, which is the first 

 symptom of the disease. The difficulty might be got rid of 

 by supposing the ergot to be a compact mycehum of a com- 

 pound nature^ formed by the sporidia of both species of 

 Claviceps concurrently ; but the mode of origin of the ergot 

 in the interior of the spermatogonium renders this supposition 

 impossible^ except upon the assumption that the spermato- 

 gonium itself is formed by the sporidia of both species, and 

 this can hardly be considered probable. The only explana- 

 tion consistent with Tulasne's theory seems to me to be, 

 that the ergot of the Phragmites, which produces Claviceps 

 purpurea, and the ergot of the same grass which produces 

 Claviceps mdcrocepliala, are essentially although not percep- 

 tibly distinct ; and that the ergot of Phragmites producing 

 Claviceps purpurea is identical with the ergot of rye, but 

 modified in size by growing upon Phragmites instead of iipon 

 rye. It is obvious that this explanation would fail if the 

 two species of Claviceps should be found upon the same 

 identical specimen of ergot, but I am not aware that this 

 has ever been observed. I do not understand fi'om Cesati's 

 statement that the two species Avere produced contempora- 

 neously, and such was not the case in the specimens which I 

 found in my own neighbourhood. 



Blackheath Park, S.E. ; 

 Eebruary, 1857. 



On the presence of Silica in the RuiuACEiE and in Achillea 

 PTARMicA. By Adolph Leipner, Esq. 



(The substance of this paper was read to tlie Bristol Microscopic Society, 

 January 14th, 1857.) 



Amongst the various inorganic elements which we find 

 present in plants, there is hardly one more interesting than 

 silica, either to the amateur microscopist or to the truly 

 scientific botanist. Some microscopic preparations of siliceous 

 parts, obtained from the Equisctacese, Graminea?, from the 

 Deutzia scabra, and some other plants in Avhich it has been 

 discovered, are rarely wanting in the limited collection of the 

 tyro, whom they please, — and never, I may say, in the 

 cabinet of the experienced physiologist, whom they still, to 

 some extent, puzzle. 



The simple fact of the presence of silica in these plants has 



