THE INORGANIC ELEMENTS. 7 



the end of the prism cut off (fig. 5. ) ; or, what is especially charac- 

 teristic, in a twin form, 

 like the gypsum crystals 

 of Montmartre. This last 

 form is found in the 

 Musacece and many Sci- 

 taminece. 



Such crystals present 

 themselves in all phane- 

 rogamous plants, but are 

 not so frequently found in cryptogamic plants. They have been described 

 amongst the latter in ChcBtophora, Hydrurus, and Chara, where they 

 exist not in the cells but in the intercellular spaces. In Polysperma and. 

 Spirogyra they are found in the cells. In the Phanerogamia they lie 

 constantly enclosed in the cells (also in the glands of the air-passages 

 of Myriophyllum*) ; more formless crystalline masses, especially of 

 carbonate of lime, are found in the intercellular passages, and upon the 

 leaves of Lathrcea ; and in many species of Saxifraga, as S. Aizoon and 

 S. longifolia, they are seen on the edges of the leaves as true excretions. 



History. The discovery of crystals in plants is due to Malpighi, who 

 first figured the glands of Opuntia (Anatome Plant, tab. xx. fig. 

 105. E.). The needle-like crystals were discovered by Jurine (Journ. de 

 Physique, 56.). Meyen and Unger have described various other forms, 

 Buchner was the first to give a chemical analysis* and thought he had 

 found phosphate of lime in them. Raspail showed that they were prin-* 

 cipally composed of oxalate of lime, which had been previously discovered 

 by Scheele in the roots of rhubarb, but forgotten. Liebig first pointed, 

 out that the vegetable acids, in all species of plants, exist combined with 

 a determinate quantity of the base, however different the base may be, 

 and that this quantity depended on the amount of oxygen combined with, 

 the base, the oxygen being always in the same proportion in the same 

 species.f The salts of ammonia were first pointed out by Saussure as 

 the source of nitrogen in plants, and afterwards further elucidated by 

 Liebig. { 



* Meyen (Physiologic, vol. i. p. 241.) appears to have overlooked the fine mem-, 

 brane which encloses these glands. 



f Liebig, Chemistry in its Applications to Agriculture and Physiology. 

 \ Op. cit. 



5 Sulphate of lime : a, simple crystal ; b and c, twin crystals. From the petioles of 

 Musa and Strelitzia. 



B 4 



