THE ASH OF PLANTS. 183 
Necessity of Chlorine for Strand Plants.—A single 
observation of Wiegmann and Polstorf, (Preisschrijt,) 
indicates that Salsola kali requires chlorine, though 
whether it be united to potassium or sodium is indiffer- 
ent. These experimenters transplanted young salt-worts 
into a pot of garden soil which contained but traces of 
chlorine, and watered them with a weak solutior of chlo- 
ride of potassium. The plants grew most luxuriantly, 
blossomed, and completely filled the pot. They were 
then put out into the earth, without receiving further ap- 
plications of chlorine-compounds, but the next year they 
became unhealthy, and perished at the time of blossoming. 
Silica is not indispensable to Crops.—The numerous 
analyses we now possess indicate that this substance is 
always present in the ash of all parts of agricultural 
plants, when they grow in natural soils. 
In the ash of the wood of trees, it usually ranges from 
1 to 3°|,, but is often found to the extent of 10-20°|,, 
or even 30° ,, especially in the pine. In leaves, it is usually 
more abundant than in stems. The ash of turnip-leaves 
contains 3-10°| ,; of tobacco-leaves, 5-18°|,; of the oat, 11— 
58°|,. (Arendt, Norton.) In ash of lettuce, 20°|, ; of beech 
leaves, 26°|,; in those of oak, 31°|, have been observed. 
(Wicke, Henneberg’s Jour., 1862, p. 156.) 
The bark or cuticle of many plants contains an extraor- 
dinary amount of silica. The Cauto tree, of South America, 
(Hirtella silicea,) is most remarkable in this respect. Its 
bark is very firm and harsh, and is difficult to cut, having the 
texture of soft sandstone. In Trinidad, the natives mix 
its ashes with clay in making pottery. The bark of the 
Cauto yields 34°|, of ash, and of this 96°], is silica. (Wicke, 
Henneberg’s Jour., 1862, p. 143.) 
Another. plant, remarkable for its content of silica, is the 
bamboo. The ash of the rind contains 70°|,, and in the 
joints of the stem are often found concretions of silica, re- 
sembling flint—the so-called Zabashir. 
