CHALK-STONES. 



[ 132 J 



CHARACE^. 



a pen-knife; then diffuse it througli the 

 water, and set it aside for a few seconds. 

 Next remove the finest particles which are 

 suspended in the water, together with most 

 of the water, and allow the remainder to 

 become perfectly dry. Moisten this re- 

 mainder with oil of turpentine, and warm it 

 over a spirit-lamp ; then add Canada balsam, 

 and digest it upon the tin-plate (iNTR.xxiv.), 

 but without its frothing. A preparation thus 

 made seldom fails ; and when magnified 300 

 diameters, the mass is seen to be chiefly 

 composedof minute well-preserved organisms. 

 As thus prepared, the cells of theForaminifera 

 first appear black, with a white central spot 

 (PI. 18, fig. 2), which is caused by air-bubbles 

 contained within the cells. The balsam gra- 

 dually penetrates into the cells, the black 

 rings of the air-bubbles disappear, and the 

 minute, frequently very elegant cells of the 

 Foraminifera become visible. See Flint, 

 and Foraminifera. 



The crystalloids are best examined in 

 common whiting, or powdered chalk which 

 has been shaken with water and set aside. 

 A veiy minute quantity removed with a dip- 

 ping tube will exhibit them. 



BiBL. The various works on geology, as 

 those of Lyell and Ansted ; Mantell, Won- 

 ders, Sfc, Medals of Creation, and y4nn. Nat. 

 Hist. 1845. xvi. p. 73 {Chalk and Flint of 

 S.E. of England); Bowerbank, Trans. Geol. 

 Soc. vi.; Ehrenberg, Ueb. d. Bild. d. Kreide- 

 fels. Sfc, Ahh. d. Berlin, Akad. 1838 (or 

 Weaver's Abstract, Ann. Nat. Hist. 1841. 

 vii.); id. Ueber lebend. Thierart. d. Kreid. 

 AbJi. d. Berl. Ak. 1840 (or Taylor's Scientific 

 Memoirs, iii. ; Morris, Catalogue of British 

 Fossils ; D'Orbigny, Bull, de la Soc. Geol. d. 

 France, iv. (or Weaver's Abst., Ann. Nat. 

 Hist. 1841. vii. p. 390). 



CHALK-STONES.— This term is vul- 

 garly applied to the white concretions formed 

 around the joints in chronic gout, or, as it is 

 sometimes called, rheumatic gout. They 

 consist of very minute needles of urate of 

 soda (PL 8. fig. 12 b). 



CHAM.ENEMA, Kiitz.— A supposed ge- 

 nus of Leptotricheous Algae, consisting of 

 dusky-coloured jointed filaments, forming 

 flocks in various syrups. Doubtless the myce- 

 lia of some Fungi, such as Penicillium. 



BiBL. Kiitzing, Sp. Alg. 158. 



CHANTRANSIA, Desv. See Trente- 



POHLIA. 



CHARA, L. See Charace^e. 

 CHARACE^.— A family of plants for- 

 merly classed among the Algae, but which, 



from the character of their reproductive or- 

 gans, evidently have a more elevated posi- 

 tion. They may be placed on the boundary 

 between the Algae and the Hepaticaceae. 

 They are remarkable for their well-known 

 ' circulation,' first discovered by Corti. The 

 Characeae are aquatic plants, of filamentous 

 structure, exhibiting elongated axes furnished 

 at intervals with whorls of branches (fig. 121). 

 In some species this axis is a simple tube 

 (fig. 128), sometimes a tube with a cortical 

 layer of smaller tubes surrounding it (figs. 

 122, 123). Some authors have divided the 

 species, on this and some other grounds, into 

 two genera, Nitella (simple tubes) and Char a 

 (corticated tubes); but, according to Al. 

 Braun, who has devoted great attention to 

 this family, the characters will not hold. 

 The mode of ramification of the simple tubes 

 is seen in figs. 128 & 129) ; that of the com- 

 pound axes is fundamentally the same, but 

 other cells arise fi-om the branch cells at the 

 articulations, one above and one below each 

 branch (C. crinita). Those on the upper 

 side of the branches grow up over the cen- 

 tral axis to meet those descending from the 

 under side of the branches of the whorl next 

 above, the ends becoming intercalated about 

 the middle of the internode ; in this course 

 of growth cell-division takes place, and the 

 primary cortical tubes are not only made up 

 of many lengths in each internode, but each is 

 perpendicularly divided into two, one large and 

 one smaller tube ( C. vulgaris), or produces a 

 secondary tube on each side (C. aspera) ; the 

 primary tubes stand out as ribs from the 

 surface. These cortical tubes describe a 

 spiral course around the internode. Fila- 

 mentous radical cells are also produced from 

 the whorls. The cells of the main axis and 

 its branches, and the primary cortical cells, 

 are those in which the circulation of their 

 contents may be best seen. The cell-wall is 

 lined by a close layer, like a pavement, of 

 chlorophyll-globules, arranged in a somewhat 

 spiral order; within them lies a thick layer 

 of semi-gelatinous consistence(the circulating 

 protoplasm), and the centre is filled up with a 

 watery fluid. The circulation in the ordinaiy 

 cells consists in the movement of the gelati- 

 nous protoplasmic sac, as one mass, slowly 

 up one side of the cell, across the ends, and 

 down the other side, not perjiendicularly, 

 however, but in an oblique or spiral course, 

 as indicated in fig. 129. The fluid in the 

 centre does not circulate, but contains vesi- 

 cles, granules, or other bodies floating in it, 

 which are free, and when resting upon the 



