126 Scientific Intelligence. 
he ‘that yielded 140 ripe seeds and had a dry weig grms. in & 
medium so free from silica that a mere trace of this substance could be 
found in the root, but half a milligramme in the stem, and 22 milli- 
grammes in the 15 leaves and sheaths. It was altogether absent from 
e seeds. 
The ash of the leaves of this plant es gt but 0°54 per cent of 
silica and the stem but 0:07 per cen ay and Ogston found in Le 
ash of maize, leaf and stem together, : ‘98 per Aina of silica. 
Knop is inclined to believe that the little silica he found in his maize 
plant was due to dust and did not belong to the tissues of the plant. He 
remarks, “J believe that silica is not to assed among the nutritive 
elements of the graminex, since I have made similar observations in the 
analysis of the ashes of barley.” 
nop does not inform us as to the firmness of the stem of tlris plant. 
It would seem however that ‘while silica is not essential to the nutritive 
in vegetation—is not required for the perfect elaboration of all 
the cells and organs of the plant—it is useful or even needful to consol- 
idate the tissues, and thus to insure the vegetable structure against me 
chanical injury. The fact of its presence in variable amount and its most 
abundant occurrence in the upper and outer parts of the vegetable struc- 
ture would indicate that: the plants which contain it in large quantity 
oppose in their root surface no obstacle to its entrance, and that within 
the plant it obeys to a great extent the ordinary laws of diffusion until it 
is made insoluble by losing the colloid and assuming the crystalloid con- 
dition ; or until it is arrested by the plant-tissues in a manner — we 
that by which fabrics of dead glintous attach to their surfaces the i 
ents of mordants and dyes; or finally until it is left in the partes call 
as a simple residue of the evaporation of the water that is perpetually 
streaming from the soil through the plant into the atmosphere. s. w. J. 
VY. MINERALOGY AND GEOLOGY. 
On a variety of Galena from Lebanon county, Pennsylvania.—The 
tetowing important _s of the at octahedral galena, from 
T 
non county, Pa., has been received from Dr. Torrey, 
" sh Grores J, Bavst. —My dear sir ‘It is now more than two years 
e I gave you specimens of galena from Lebanon county, Penney" 
nia, abel exhibited a serhAeNoly distinct octahedral cleavage. It W 
to me to be assayed for silver, and proved to be highly argentifer- 
ous, containing 1794 ounces of silver to the ton. From the same locality 
there were other specimens of galena, even richer in silver, but having t 
