On the Siliceous Deposit in the Cortex of 
Certain Species of Selaginella, Spr. 
BY 
R. J. HARVEY GIBSON, M.A., F.L.S. 
Lecturer on Botany in University College , Liverpool. 
With Plate XVIII. 
HE existence of a mineral incrustation on the cortical 
J- wall of the lacuna of Selaginella Martensii , Spr. is well 
known to botanists ; but, so far as I am aware, no account has 
been published of the exact nature, distribution and mode of 
origin of this mineralization, nor has its presence in any other 
species of the genus been noted. In discussing the structure 
of the stele in 5. Martensii , Strasburger 1 casually mentions the 
presence of the deposit, but gives no details. 
Whilst engaged last winter on a research into the comparative 
anatomy of the genus Selaginella in the Botanical Laboratory 
of the University of Strassburg, Graf zu Solms suggested to 
me that it might be worth while to examine the deposit in 
some detail, and to determine its exact chemical character, 
distribution, and mode of origin in the species, and also to 
investigate whether similar deposits were to be met with in 
other species of the genus. I have examined in all fifty-two 
species of Selaginella , for material of which I am indebted to 
1 Ueber d. Bau. u. d. Verricht. d. Leitnngsbahnen in d. Pflanzen : ‘ Hingegen 
sind an letzteren oft unregelmassige, sprode, farblose Belege zu sehen, die 
Kieselsaure zu sein scheinen.’ 
[Annals of Botany, Vol. VII. No. XXVII. September, 1893.] 
B b 
