MORPHOLOGY OF THE CELL. 



consislinp: of a peculiar substance, which we call Cellulose (Fig. i, B, C, h). Close 

 to the inner side of this membrane, which forms a closed envelope, is a second 

 layer, also entirely continuous, the substance of which is soft and inelastic, and 

 which always contains albuminous matter; to this substance H. v. Mohl gave the 

 distinctive appellation of Protoplasm ^ In the cells now under consideration it 



forms a sac enclosed by the 

 cell-wall, in which sac other 

 portions of protoplasm are 

 also usually present in the 

 form of plates and threads 

 (Fig. I, B, C, /). Absent 

 from some of the lowest or- 

 ganisms, but present in all the 

 higher plants without excep- 

 tion, there lies imbedded in 

 the protoplasm a roundish 

 body, the substance of which 

 is very similar to that of the 

 protoplasm, the Nucleus {A, 

 C, k). The cavity enclosed 

 by the protoplasm-sac is filled 

 with a watery fluid, the Cell- 

 sap (B, C, s). In addition to 

 these, there are also very com- 

 monly found in the interior of 

 the cell granular bodies, which 

 however may be passed over 

 for the present. 



Cells, in the stage of deve- 

 lopment now described, consist 

 therefore of a firm membrane, 

 semi-solid protoplasm (includ- 

 ing the nucleus), and fluid cell- 

 sap. At first, however, the cell- 

 sap is wanting. If the same 

 cells are examined in a very 

 early stage of their development they are smaller (A), their cell-wall thinner, and 

 the protoplasm forms a continuous mass, in the middle of which lies the nucleus, at 



FIG. I. — Parenchymatous cells from the median cortical layer of the root of 

 Fritillaria impcrialis ; longitudinal sections ( X 550). A very young cells lying- 

 close to the apex of the root, still without cell-sap. B cells of the same description 

 about 2 mm. from the apex of the root, the cell-sap s forming separate drops in the 

 protoplasm/; between the drops are plates of protoplasm; C cells of the same 

 description about 7 — 8 mm. from the apex of the root ; the two cells to the right 

 below are seen in a front view ; the large cell to the left below is in optical section ; 

 the cell to the right above is opened by the section ; the nucleus shows, under the 

 influence of the penetrating water, a peculiar appearance of swelling (x, y). 



^ H, V. Mohl, Ueher die Saftbewegungen im Inneren der Zellen, Bot. Zeitg. 1846, p. 73. The 

 importance of this substance to the life of the cell was recognised at the same time by Nageli, 

 who, in conjunction with Schleiden, termed it ' Schleim.' (Zeitschr. fiir wissensch. Bot. von 

 Schleiden u. Nageli, Heft III, 1846, p. 53.) [The 'nucleus' was figured by F. Bauer in 1830 in 

 the stigmatic cells of Bletia TankervillicE from a sketch made in 1802. Meyen in the former year 

 i?idicated it in his ' Phytotomie.' It was first described by Robert Brown (see Misc. Bot. Works, vol. I. 

 p. 512) in 1833. Schwann in 1839 applied the term 'nucleolus' to the body previously discovered 

 by Schleiden (Schwann and Schleiden's Researches, p. 3). Cohn in 1850 pointed out the analogy 

 of the ' protoplasm ' of botanists with the ' sarcode ' of zoologists.] 



