66 MORPHOLOGY OF THE CELL. 



and from all Abietineae that have been examined. The small angular granules or 

 larger individual crystals are usually deposited in the soft lamella between the 

 elements of the bast-tissue. Much more widely distributed even than in their bast, 

 calcium oxalate occurs deposited in the cell-wall of the primary cortical paren- 

 chyma of the branches and leaves of Gymnosperms, with the possible exception 

 of some Abietineae ; here also the middle lamella of the common wall between 

 each two cells is the place where the crystals are formed, as also in the bundles 

 of thick- walled cells beneath the epidermis {e. g. Ephedra). The thick- walled 

 often branched fibre-cells abundantly scattered through the parenchymatous tissues 

 of Gymnosperms, the so-called ' spicular cells,' not unfrequently contain crystals 

 deposited in their outer mass of layers ; these occur in unusually large numbers 

 and great perfection in Welwitschia mirabilis. If the crystals are dissolved in 

 hydrochloric acid, the empty cavities in the substance of the cell- wall retain com- 

 pletely the form of the crystals, so that the unpractised observer thinks that he 

 still sees them. Finally, fine granules are abundantly scattered through the thick- 

 ened outer wall of the epidermis of Gymnosperms (Welwitschia, ' Taxus baccata, 

 Ephedra, &c.) or, in other cases, well-developed small crystals (Biota orienialis, 

 Libocedrus Doniana, Cephalotaxiis Fortunei, &c.). 



Connected with these deposits in the cell-wall itself are the clusters of crystals 

 discovered by Rosanoff (Bot. Zeitg. 1865, 1867) in the pith of KePria japonica, 

 Riciniis communis^ and in the leaf- stalk of different Aroideae (Anthurium, Philoden- 

 dron, and Pothos), which, lying in the cavity of the cell, are united with the cell- 

 wall by simple or branched threads of cellulose, and are even covered with a 

 membrane of cellulose. 



The crystalline forms in which the calcium oxalate occurs in the cells of plants 

 are extremely numerous, an immediate consequence of the circumstance that this 

 salt crystallises in two different systems, according as it is combined with six or with 

 two equivalents of water. The calcium oxalate containing six equivalents of water 



of crystallisation ^^ ^Cfi^-\-^ 2l(\\ crystallises in the quadratic system, the fun- 

 damental form is an obtuse quadrate-octahedron (envelope-shaped) ; combinations 

 of the quadratic prism with the obtuse octahedron are met with in abundance. The 

 raphides, however, belong, as respects their behaviour in polarised light, according 

 to Holzner, to the klino-rhombic system, in which calcium oxalate crystallises with 



two equivalents of water of crystaUisation y^ Q^QOg-f- 2 aq. j. The fundamental 



form of the numerous combinations belonging to this class is a hendyohedron ; it 

 produces derivative forms which are very similar to calcspar (as, for instance, in the 

 deposits in the cell-wall), and others very similar to calcium sulphate. The clusters 

 of crystals may consist of individuals of one or the other system. 



On the physiological signification of calcium oxalate what is necessary to be said will 

 be found in Book III. ch. 2. Here however a few remarks may be made on the 

 directly recognisable relation of the crystals to the cells which produce them. 



When the crystals remain so small that their volume appears inconsiderable in rela- 

 tion to that of the cell itself, this latter retains its usual character; it may possess 

 protoplasm, nucleus, chlorophyll, and starch (as in the case of the hairs of Gucurbita or 



