CRFSTALS IN THE CELLS OF PLANTS. 63 



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

 difference is very great. 



Calcium carbonate occurs, v^^here it has hitherto been observed in plants, not 

 in the form of large crystals with clearly defined faces, but in 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 as 

 calcium carbonate. It occurs, according to De Bary, in the form of roundish 

 grains in the plasmodium of Physarum. The calcium carbonate imbedded in 

 the cell-walls of many marine Algse, Acetalularia, Corallina, Melobesia, &c., seems 

 to be still more finely divided, their structure becoming in consequence stony and 

 brittle. It occurs in an excessively fine state of division, in the form of molecules 

 .invisible even under a magnifying power of 800, in the structures known as 

 Cystoliihs, club-shaped outgrowths of the walls of certain cells projecting into 

 ;^ e cavity, found in Urticaceae and Acanthaceae {vide infra). 

 BB, 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 

 r jsolubility in acetic acid, and their solubility in hydrochloric acid without evolution 

 |H| bubbles, to consist of Calcium oxalate. This salt is widely distributed, especially 

 ^H the tissue of the Crustaceous Lichens, most Fungi, and Phanerogams, and in 

 ^He form of very small granules of crystalline structure, of clusters, of bundles of 

 nieedles {Raphides), or often of large, beautiful individuals with perfectly formed 

 crystalline flices. 



In Fungi and Lichens the crystalline granules are commonly small, and are 

 not deposited in the interior of the cells, but on the outside of the cell-walls, 

 and frequently in such large numbers that the hyphal tissue becomes opaque and 

 brittle in consequence. In some Lichens, as in Psorosma lentigerum, according to 

 De .Bary, minute granules of calcium oxalate are deposited in the cell-walls of 

 the dense cortical tissue. It is only exceptionally that crystalline deposits occur 

 in the interior of the cells of Fungi, as, for example, in the form of radiate 

 spheres (sphere-crystals) in the swellings of some of the hyphse of the mycelium of 

 Phallus caninus. 



Little or nothing is known of the occurrence of calcium oxalate in most Algae, 

 in Muscineae, and in Vascular Cryptogams ; but it is found very abundantly in the 

 tissues of most Phanerogams. In Dicotyledons it often occurs in the form of 

 large beautifully perfect Crystals in the cavities of cells {e.g. in the mesophyll and 

 petiole of Begonia, and the stem and root of Phaseolus). Clusters of crystals 

 are, however, much more common in this class, and are especially abundant in 

 •the bark of many trees, in the rhizome of Rheum, &c. They are deposited in a 

 protoplasmic nucleus {e.g. in the cotyledons of Cardiospermum Halicacabum), the 

 separate crystals being completely formed only in the exposed part. Sometimes 

 also (as in the hairs of Cucurbita) small and perfectly developed crystals are seen 

 in the circulating protoplasm. 



In Monocotyledons, especially those allied to the Liliaceae and Aroideae, the 

 crystals of calcium oxalate occur mostly in the form of bundles of long very slender 

 ^Jjeedles, forming the so-called Raphides, which lie parallel to one another, and 



