THE PEIMITIVE CELL. 



tiieir elementary composition, structure, habits, and the 

 vital laws that govern them ; and secondly, we regard 

 them in what may be termed their social or relative con- 

 ditions, as forming groups — species, genera, tribes, orders 

 and classes. The first comprehends Vegetable Anat- 

 omy, Structural and Physiological Botany, and the last 

 Systematic Botany. 



23. Under the first of these distinctions, in which 

 Natural History becomes a kind of biography, the Plant 

 will now be presented to your view ; and if you attend to 

 this branch of the study with a loving mind, you may safely 

 promise yourselves a rich reward; for in nothing are plants 

 more beautiful, more wonderful, than in their anatomical 

 perfection, the minute elemepts of their organism. 



24. A knowledge of the elementary composition 

 and intimate structure of those organs of which plants 

 are composed, is termed Vegetable Anatomy. This 

 may properly be considered the basis of the whole science, 

 since, if we thoroughly understand the parts, we can 

 more clearly and truly comprehend the whole. 



25. Let us take up the Convolvulus again, and make 

 a few more observations. At a glance we are struck 

 with a great dissimilarity of structure in the substances 

 of which its different organs are composed. In a single 

 leaf we find certain soft, succulent parts, which form the 

 expansion, or blade, and a fibrous portion that makes the 

 frame-work, its stalk and veins. But these differences 

 Become more apparent and remarkable when we throw 

 them into a stronger contrast. What could be more 

 unlike each other than the tough wood or coarse bark of 

 a forest tree, and the delicate petals of this little flower ? 

 In order to perceive the reason of these differences, we 

 must have recourse to the Microscope. 



26. FmsT EoEM of the Cell. — Let us take a 

 small piece of this Melon leaf, and place it so that its 

 cut edge, or thickness, will be presented to the action of 

 the lens (see fig. 6). We now find, instead of the plain 

 surface that appeared to the naked eye, a collection of 

 roundish sacs or bladders, that look somewhat like little 

 green eggs. Of these the whole substance, except the 

 stalk and veins, is composed ; and because they are closed 

 on all sides, like small chambers, they are called cells. 

 The upper cells are seen at ii, the lower ones at Z ; h, a 

 hair ; c, one of the canals connected with the breathing 

 pores ; s, spaces between the lower cells ; and/, a bundle 

 of fibre. 



27. Here we have arrived at the basis of the whole 



Subject or tho chapter. Two general aspects of the science. Plants as 

 Individuals — stud/ comprehends what? Plants in Groups — what? Which 

 division have you now entered on? Define Vegetable Anatomy. Observa- 

 tions on the Plant. Differences observed. Mioroscopic observation. What 



structure. This minute and delicate cell-work is the 

 parent of all the vegetable tissues, from the tender floret 

 that blooms and fades in a single day, to the heart of 

 Oak, that only hardens with the storms of centuries ; the 

 Mushroom, that lives, and grows, and perishes in an 

 hour; the Herb, Shrub, or Tree, whose life may be 

 measured by months, or years, or ages, from the little 

 Bell-flower, that blossoms at our feet, to the giant Plane- 

 tree of the primeval woods, may each be traced to- a com- 

 mon origin — in a cell-work so minute, that only by help 

 of the microscope can we detect its presence. All these 

 very different structures are built up of the same mate- 

 rial. The elements are few and simple, but their combi- 

 nations are infinite. 



28. A plant may be considered as an assemblage of 

 cells, out of which its whole fabric is wrought in a contin- 

 uous series, like a piece of lace-work ; and so simple is 

 the mechanical arrangement, that a little child may com- 

 prehend it ; while the wisdom of Sages may find subject 

 for study in the contemplation of its vital laws. 



29. Appearance op the Cells. — Sometimes they 

 represent a delicate net-work, as may be seen in the pith 

 at a, fig. 2, which represents a section of a woody stem. 

 They are oblong, and flattened in the bark, as at hh, 

 while at i i and e e they have nearly the same form ; and 

 because they seem to be woven, or wrought together, the 

 different textures thus formed are called Tissues. These 

 in the course of growth assume various modifications, 

 and receive different names. The primitive tissue of 

 plants is the Cellular Tissue, the component parts 

 and combinations of which we are now to consider. 



30. Structure of the Cell. — The walls are formed 

 of a firm, colorless, semi-transparent membrane, and 

 during its whole life they remain closed on all sides. 

 The substance of this membrane is composed of carbon, 

 hydrogen, and oxygen, and is called Cellulose. The 

 inner surface of the walls is coated with a viscid, yellowish- 

 semi-fluid substance, which, in addition to the elements 

 of pure cellulose, has a small portion of nitrogen, the 

 latter substance being always necessary to vital action. 

 Here, in this inner coating of its Sells, the substance of 

 which is called Protoplasm, all the vital forces of the 

 plant reside. Here are wrought all those marvellous 

 changes, which, the more we know them, the more do 

 they call forth our admiration and astonishment ; to wit- 

 ness, from means so few and simple, results so rich, and 

 varied, and manifold. 



discovered? What called? Why? Parent of tissues. (27) What may a 

 plant be considered? Appearance of tho cells. Why called Tissues ? Prim- 

 itive Tissue. Structure of the Cell. Substance of its walls. Of their semi- 

 fluid lining. In which is the vital action maintained ? 



