476 Linnean Society. 
Mr. William Cumming presented specimens of Lagurus ovatus, 
Briza maxima, and Mentha crispa, gathered by him in the vicinity of 
Saffron Walden, Essex. 
Read, ‘“‘ On a White Incrustation on Stones, from the bed of the 
river Annan.” By Edwin Lankester, M.D., F.L.S. 
During a- short stay which the author made last summer on the 
banks of the Annan, in Dumfries-shire, his attention was arrested by 
the appearance of the stones on the banks of the river. Wherever 
a mass of gravel was exposed to the air, the surface of the stones 
appeared covered with a white incrustation, as if they had been 
white-washed.. This appearance was more or less general on all 
the exposed banks, but was most evident on the stones nearest the 
water’s edge. On examining the stones with a pocket-lens, their 
surface appeared covered with acicular crystals, and from this it 
was at first concluded that the incrustation arose from the crystalliza- 
tion of some salt abounding in the waters. On procuring, however, 
some stones from the water itself, they presented on their surfaces 
the filaments of a minute conferva, which appeared to be the source - 
of the white crust; but as the existence of the conferva would not 
explain the crystalline appearance, it was examined under the micro- 
scope, and the appearance was found to proceed from minute acicu- 
lar bodies about ;45th of an inchlong and 3,55th of an inch broad, 
which were most of them arranged in a stellate form, but many 
were scattered in all directions. Running under the whole were 
the filaments of a minute conferva, on which the acicular bodies 
rested. 
In Greville’s Scottish Cryptogamic Flora, these bodies are referred 
to the genus Hzilaria, but the stellate arrangement of the aciculz 
gave them a different character to E. fasciculata. Hooker, in his 
continuation of Smith’s‘ English Flora,’ has placed Greville’s supposed 
plant as a synonym of Diatoma truncatum, from which D. fascicula- 
tum is not distinct. 
In Ehrenberg’s great work on the Infusoria, these bodies are 
figured and described under the head of Polygastric animalcules 
(p. 11. tab. xvii.) of the family Baccillarie. ‘The genus to which 
they belong is Synedra, and is distinguished by the animal being 
furnished ‘‘ with a simple siliceous prismatic carapace, when young 
attached by one end, when old often free, without any or only a 
slightly marked pedicel.’’ The species which it most closely re- 
sembles is the Synedra Ulna (common Eel-animalcule), which is 
characterized by being striated with linear corpuscles, straight, trun- 
cated at the sides, flat on the back and belly, with the apex a little 
dilated as they become aged. The bodies from the Annan are not 
striated, nor are their ends dilated, although they appear full-grown. 
The siliceous skeletons in which these little animals are invested, 
will account for their white appearance. Although these bodies 
have been often described both as plants and animals, no notice 
appears to have been given of their producing the phenomenon 
here described. 
