CR FS TA LS IN THE CELLS OF PLANTS. 
65 
to be described; both from a morphological and physiological point of view the 
difference is very great. 
Calcium carbonate occurs, where 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 
Hght (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 Alg3e, Acetabtdaria, Corallifia, 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 
Cystoliths, club-shaped outgrowths of the walls of certain cells projecting into 
the cavity, found in Urticaceae and Acanthacese {vide infra). 
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 
insolubility in acetic acid, and their solubility in hydrochloric acid without evolution 
of bubbles, to consist of Calcium oxalate. This salt is widely distributed, especially 
in the tissue of the Crustaceous Lichens, most Fungi, and Phanerogams, and in 
the form of very small granules of crystalline structure, of clusters, of bundles of 
needles {Raphides), or often of large, beautiful individuals with perfectly formed 
crystalline faces. 
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 lentigeriim, 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 hyphae of the mycelium of 
Phallus cajtinus. 
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 iji 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 Rheim, &c. They are deposited in a' 
protoplasmic nucleus {e. g. in the cotyledons of Cardiospennimi Halicacabuiii), 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 Liliacese and Aroideoe, the 
crystals of calcium oxalate occur mostly in the form of bundles of long very slender 
needles, forming the so-called Rafhides, which lie parallel to one another, and 
F 
