PHENOMENA OF GROWTH. 163 



pleted cells, fibres, and vessels are no longer active ; their 

 builder has left them. They are now storehouses, techni- 

 cally called Formed material; this makes the greater part 

 of all trees, including every part except the active cells, 

 which are in and near the cambium and in the paren- 

 chyma. 



401. Formed material stored up in the latieiferous vessels is finely 

 exhibited in the Borneo camphor-trees. The best camphor is in the 

 heartwood. It is found by making repeated incisions in the large, 

 fine trunks of the older trees. When camphor is discovered, the tree 

 is felled and cut into logs, which are carefully split by experts. The 

 camphor is then removed with sharp instruments, the masses being 

 often a foot and a half long and as thick as a man's arm. Valuable 

 as it is, however, it seems a shame that so many noble trees should be 

 sacrificed in the search for it when a good quality is furnished by less 

 beautiful trees in other Orders. 



402. Inorganic Constituents. — If we burn a plant, only 

 a few ashes remain ; all the other parts are reconverted into 

 air and vapor. These ashes are mineral (inorganic) ; they 

 consist of Potash, Soda (in marine plants), Silex, or Silica, 

 Lime, Magnesia, Iron, Manganese, Sulphur, Phosphorus, 

 Chlorine, and a few other elements, those in greater propor- 

 tion being mentioned first in this list. But they do not enter 

 into the real texture of the plant; and they never make 

 more than 1 to 10 per cent, of its fabric. Many of these 

 elements seem to be taken up by mere physical force (capil- 

 lary attraction) into the cell, and are left incrusted there 

 after its fluids have been consumed. 



403. Yet the plant evidently likes certain of them, which are invari- 

 ably found in it. To some plants they seem to be necessary, as chlo- 

 rine to Buckwheat. Silex is abundant in the Grasses (giving strength 

 to their slender stems), so that the rind, when split, often cuts the flesh 

 like a knife. We have already seen how the Diatoms clothe them- 

 selves with it. 7'abasheer, so prized as a remedy by Eastern physicians 

 and so interesting to the chemist, is a secretion in the latieiferous ves- 

 sels about the joints of the Indian Bamboo. It occurs in lustrous, 

 pearl-colored masses, and is purely mineral, consisting of 70 parts of 

 silica and 30 of potash and chalk. " It is indestructible by fire, resists 

 all acids, unites by fusion with alkalies into a white, opaque mass, or 

 into a permanent, transparent glass ; and is again separable from these 

 compounds, being unchanged by acids." — Hogg. 



404. Besides the latieiferous vessels, special cells are 

 found containing minerals which have crystallized in 



