ANALYTICAL CLASS-BOOK OF BOTAlfY. 



31. FORMS or TH* CELL. Very young plants, 

 whatever they are destined to become, contain only the 

 rudiments of fibre ; and their whole substance may be 

 raid to consist of roundish or oral colls, as you hare seen 

 at fig. G. But as the adjacent parts multiply and enlarge, 

 the cells, being compressed on all sides, assume a twelve- 

 form, and in the mass hare the appearance of an 



irregular honeycomb. This is well shown in the highly 

 magnified section of Elder pith, fig. 7. There is a great 

 variety in the forms of the cell, and some of them are 

 extremely elegant When subjected to pressure on two 

 opposite sides, they become flattened. This form uni- 

 versally occurs in the cells of the outside integument, or 

 skin, of plants. A row of these flattened cells may be 

 seen at the upper and under surfaces of the Melon leaf, 

 fig. 6, and also in the bark and some other parts of the 

 section of wood, fig. 2. Sometimes the cells assume the 

 ranee of prisms or cylinders ; here they are spindle- 

 shaped, there they are drawn out into long tubes or flat 

 filaments, and again they become stellate, and take the 

 shape of beautiful little stars. 



32. LIFE OF THE CELL. The cell walls, though 

 entirely closed, are penetrable by liquids, and through 

 them every cell sucks up as much as it needs of the nu- 

 trient matter that surrounds it. This being acted on 

 by the vital forces, a chemical change takes place, and a 

 separation occurs. The nutritive portion is taken up fur 

 the nourishment and support of the tissues, while the 

 remainder is-fipclled, as useless. In these acts the life 

 of i lie cell essentially consists ; and the life of the whole 

 plant, which is but an aggregation of cell lives, can be 

 but a repetition of the same processes. 



33. GnowTH OF THE CELL. The nutrient matter 

 thus absorbed is applied to the interstices of the cell 

 wall*, which, if no obstacle intervene, extend themselves 

 in all directions, until they reach a definite size, when 

 they are either absorbed by new cells, or they remain 

 permanently fixed. Having once attained to a full 

 growth, their vitality gradually diminishes, until at 

 length they cease to have any part in the actions of life. 

 Each individual cell may be considered as an independent 



. organism, having its own particular life, which it may be 

 aid to support by its own labor ; and though, like the 

 Corals, Sponges, and some higher animals, the Cells live 

 in a community, yet each of them, BO long as it exists, 

 always maintains its own individual life, character and 

 action, truly as any of these. 



34. MULTIPLICATION OF CELLH. When the nutrient 



material has accumulated in a sufficient degree for tho 

 support of the new cells, they immediately begin to bo 

 formed. There are two principal modes of cell forma- 

 tion first, by partitions, and secondly, by gemmation, or 

 BCDDINO, from the free extremity. 



(1.) By PARTITION. Tho cell lining is infolded, 

 until its extending edges meet and eoliere, when a double 

 wall of cellulose is deposited, to strengthen and sustain 

 the new structure. Thus two, four, eight, or e\ 

 greater number of Daughter-cells arc formed, while gene- 

 rally the Mother-cells are absorbed in the new growth; 

 but sometimes they remain. 



(-.*.) GEMMATION-. In this form there is a regular 

 growing point, from which buds are protruded. Some- 

 times the cells thus formed are again multiplied by ]>:ir- 

 tition, and thus both modes arc combined. Some of the 

 microscopic plants that develope in fermenting infusions, 

 as the Yeast plant, are said to grow by gemmation, 

 while in many of the fresh-water plants known as Con- 

 fervas, both forms are observed. The production of new 

 cells sometimes goes on with inconceivable rapidity 

 This may bo seen in tho rapid growth of the common 

 Mushrooms, which are composed entirely of cellular 

 tissue. These frequently spring up and grow to tho 

 height of several inches in a single Bight ; and in one of 

 them it has been computed that twenty thousand new 

 cells are formed every minute ! The growth of Mush- 

 rooms, like all vegetable growth, consists entirely of a 

 multiplication of cells. 



35. PARENCHYMA. Cellular tissue collectively is 

 called PARENCHYMA, and sometimes it is convenient to 

 have this distinctive term. When tho cells arc equally 

 flattened on all sides, as in tho pith of Elder, fig. 7, 

 tho parenchyma is COMPLETE ; when they are not sub- 

 jected to equal pressure, as in the Melon leaf, fig. G, it is 



INCOMPLETE. 



36. ORIGIN OF THE CELL. This is not, as yet, 

 very clearly established ; but a certain little body 

 termed tho NUCLEUS is supposed to play an important 

 part in the process, because in the structure of cells it is 

 seen that the particles arrange themselves around this 

 as a common centre. It is not, however, always present. 

 In fig. 5 are represented two cells of the Snowberry, each 

 with its nucleus, a. There are also various currents to 

 bo seen, cither proceeding from or toward the nucleus, 

 their direction being indicated by arrows. These cur- 

 rents are, without doubt, a result of the vital action in 

 the azotized semi-fluid lining of the cell wall, by which, 



Formi.rib.cJl. I*. Growth. Multlpllotlon. The two model 

 WhB/lftTUulCOb*eoQjtdr*dr luuacaofnpld powth PIT- 



nohym*. When complete Incomplete ? Origin of the OIL Wb>t Im- 

 portant pvtr Iltmlwj-iprc*cntJ 



