64 MORPHOLOGY OF THE CELL. 



well as by their appearance. If masses of tissue containing much inuline (tubers of 

 Inula Heknium and Heliantbus tuberosus, roots of dandelion and of other Compositae) are 

 examined in the dry state, the parenchyma-cells are found to be filled with angular, 

 irregular, shining, colourless fragments, which are seen in polarised light to be crystal- 

 line, and may be recognised as inuline by the reactions above-named. 



If the ovaries and unripe fruits of the orange or citron are laid for some time in 

 alcohol, concretions are found in their tissues, which completely resemble in form the 

 sphere-crystals of inuhne ; but the chemical reactions and the degree of solubility show 

 that they do not consist of this substance. 



Sect. ii. Crystals in the Cells of Plants \ — The crystalline forms de- 

 scribed in sect. 7, in which albuminoids are sometimes found, though always mixed 

 with other organic compounds, are not common phenomena, and must not be 

 placed in the same category as the very abundant true crystals of lime salts now 

 to be described ; from a morphological and physiological point of view the differ- 

 ence is still more essential. 



Calcium carbonate occurs, where it has hitherto been observed in plants, 

 not in the form of large crystals with clearly defined surfaces, but in that of 

 finely granular deposits whose crystalline nature is recognised only by their 

 behaviour to polarised light (illuminating in a dark field of view by a crossed 

 Nicol) ; while their solubility in weak acids with evolution of bubbles of gas, 

 characterises them (under the circumstances named) as calcium carbonate. It 

 occurs thus, according to De Bary, in the form of roundish grains in the Plasmo- 

 dium of the Physariae. In the epidermis-cells of the leaves of many Urticaceae 

 (Ficus, Morus, Broussonetia, Humulus, Boehmeria, &c.), and in the stem of species 

 of Justicia, stalked, club-shaped, stratified out-growths of the cell-wall are formed, 

 by peculiar increase of thickness, projecting into the cavity of the cells. In the 

 substance of these masses of cellulose ' are deposited clusters of very small micro- 

 scopic crystals of calcium carbonate, which singly are scarcely or not at all 

 distinguishable, and which, as their behaviour on illuminating with polarised light 

 shows, are arranged in a radiate manner in each single cluster (group of crystals) 

 around its centre.' (Hofmeister, /. c.) These structures are known as Cystoliths. 

 The lime deposited in the cell-walls of many marine Algae appears to be still more 

 finely divided ; their structure becoming in consequence stony and brittle. {Ace/a- 

 bularia, Corallina, Melobesiaceae, &c.) 



All other crystals found in plants and hitherto accurately examined are shown, 

 by their form where this is recognisable, and by their reactions, especially by their 

 insolubihty in acetic acid, and their solubility without evolution of bubbles in hydro- 

 chloric acid, to consist of Calcium oxalate. This salt is widely distributed, especially 

 in the tissue of crustaceous Lichens, most Fungi and Phanerogams, and in the 

 form of very small granules of crystalline structure, of clusters, of bundles of needles 

 (Raphides), and often of large, beautiful individuals with perfectly formed crystalline 

 surfaces. 



^ Sanio, Monatsber. der Berl. Akad. p. 254, April 1857. — Hanstein, ibid. Nov. 17, 1859. — 

 Gg. Holzner, Flora, pp. 273, 556, 1864, and p. 499, 1867.— G. Hilgers, Jahrbuch fiir wiss. Bot. VI, 

 p. 285, 1867.— Rosanoff, Bot. Zeitg. 1865 and 1867.— Solms-Laubach, Bot. Zeitg. nos. 31-33, 1871. 

 — Hofmeister, Lehre von der Pflanzenzelle, Leipzig 1867 ; cystoliths are treated of at p. 180. 



