BOOK I. 



GENERAL MORPHOLOGY, 



CHAPTER I. 

 MORPHOLOGY OF THE CELL. 



Sect. i. Preliminary Inquiry into the Nature of the Cell. — The 



substance of plants is not homogeneous, but is composed of small structures, 

 generally indistinguishable by the naked eye ; and each of these, at least for a time, 

 is a whole complete in itself, being composed of solid, soft, and fluid layers, different 

 in their chemical nature, and disposed concentrically from without inwards. These 

 structures are termed Cells. For the most part, a group of them are in close contact 

 and firmly united ; they then form a Cell-tissue. But every plant which completes 

 its term of life has at least one period in which certain cells separate themselves 

 at definite points from the union, and, after isolation, each begins for itself a 

 separate course of life (spores, pollen-grains, ovum-cells, gemmae). 



The shape and size of the whole plant, the form, structure, and volume of 

 the cells are subject to regular changes, and their nature cannot therefore be 

 inferred from the knowledge of one single phase, but rather from the sum of 

 changes which may be called the life-history of the cell. And as, moreover, each 

 cell fulfils its own definite part in the economy of the plant, i. e. is specially intended 

 for certain chemical or mechanical purposes, so also cells show a variety in form, 

 which corresponds to the different functions. These differences, however, do not 

 usually arise until the cells have passed through their earlier stages; the youngest 

 cells of a plant are only slightly distinguishable from one another. 



The law of configuration that prevails in all cells is also more clearly evident 

 in the young state ; the more the developing cells assume the special purposes for 

 which they exist, the more difficult it becomes to recognise this law. The morpho- 

 logical law of cells, thus briefly pointed out, we will now endeavour to expound 

 more in detafl. 



By far the largest proportion of cells in the living succulent parts of plants, 

 e. g. young roots, lea^ves, internodes, fruits, are seen to be made up of three 



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