THE ASH OF PLAINTS. 183 



Necessity of Cblorinc for Strand Plants.— A single 

 observation of Wiegmann and Polstorf, {Preisschrift,) 

 indicates that Salsola Jcali requires chlorine, though 

 whether it he united to potassium or sodium is indiffer- 

 ent. These experimenters transplanted young salt-worts 

 into a pot of garden soil wliich contained but traces of 

 chlorine, and watered them with a weak solution of cl do- 

 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 3-1 0°] „ ; of tobacco-leaves, 5-18° I,, ; 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 tToitr., 1862, p. 156.) 



The bark or cuticle of many plants contains an extraor- 

 dioary amount of silica. The Cauto tree, of South America, 

 {Strtella silicea,) is most remarkable in this respect. Its 

 bark is very firm and harsli, 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, 

 ITenneberg^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 Tabashir. 



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