124 Scientific Intelligence. . 
4. On the occurrence of Silica in the higher Planits.—The existence of 
considerable quantities of silica in the bamboo, in the equisetums, in the 
es and sedges has long been known. 
@ numerous analyses of the ashes of plants which we now possess, 
indicate that this substance is an invariable ingredient of the higher 
plants when they grow in natural soils. We find it in fact in nearly all 
parts of agricultural and forest plants. The seeds of the bean, quince, 
lemon, madder and flax are among the few parts of plants in which it 
has not been detected. : 
In the ash of the wood of most common forest trees, it ranges from 1 
to 3 per cent; in the Carpinus betul it is as high as 4-97 per cent, (Fr. 
Schulze): in the Pinus sylvestris, 8:39 per cent, (Levi): in the Pinus 
picea 20°01 per cent, (Hertwig). 
~ In the ash of leaves silica is more abundant than in that of wood. The 
ash of turnip leaves contains 3 to 10 per cent, (Anderson); of Pinus picea, 
10-79 per cent, (Fr. Schulze); of the hop, 12°14 per cent, (Nesbit) ; of to 
nts. 
The position of silica in the plant is seen, from the percentages above 
quoted, to be, in general, at the surface. Although it is found in all parts 
of the plant, yet the cuéiele is usually richest, and this is especially true 
in cases where the content of silica is large. Davy in 1799 drew aften- 
tion to the deposition of silica in the cuticle, and announced the idea at 
it serves the plant an office of support similar to that enacted in animals 
by the bones, ‘ 
That silica assumes the form of the cells in the cuticle of the Equise- 
tums and Deutzias, is well known, Kindt finds that the bairs of nettles, 
Wicke that the hairs of hemp, hops and other rough leaved plants esi 
in with silica, According to Wicke the leaves of many forest 
and fruit trees when cautiously incinerated, leave a silicious skeleton that 
preserves the form of the epidermis. Mohl has minutely studied the po 
Sition assumed by silica in many plants. He finds that in some leaves, 
