DIFFERENCES BETWEEN ANIMALS AND PLANTS 



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It has been already mentioned that in animal cells an envelope or cell-wall 

 is by no means always present. In adult vegetable cells, on the other hand, 

 a well-defined wall is highly characteristic; this is composed of cellulose, 

 is non- nitrogenous, and thus differs chemically as well as structurally from the 

 contained protoplasmic mass. Moreover, in vegetable cells, figure 12, B, the 



FIG. ii. Karyokinesis, Mitosis, or Indirect Cell Division (diagrammatic). A, Cell with rest- 

 ing nucleus; B, wreath, daughter centrosomes and early stage of achromatic spindle; C, chromo- 

 somes; D, monaster stage, achromatic spindle in long axis of nucleus, chromosomes dividing; 

 E, chromosomes moving toward centrosomes; F, diaster stage, chromosomes at poles of nucleus, 

 commencing constriction of cell body; G, daughter nuclei beginning return to resting state; H, 

 daughter nuclei showing monaster and wreath; 7, complete division of cell body into daughter 

 cells whose nuclei have returned to the resting state. (After Bohm and von Davidoff .) 



protoplasmic contents of the cell fall into two subdivisions: i, a continuous 

 film which lines the interior of the cellulose wall; and, 2, a reticulate mass con- 

 taining the nucleus and occupying the cell-cavity. The interstices are filled 

 with fluid. In young vegetable cells such a distinction does not exist; a 



FIG. 12. A. Young Vegetable Cells.Showing Cell-Cavity Entirely Filled with Granular Pro- 

 toplasm Enclosing a Large Oval Nucleus, with one or more Nucleoli. B. Older cells from same 

 plant, showing distinct cellulose- wall and vacuolati.on o f protoplasm. 



finely granular protoplasm occupies the whole cell-cavity, figure 12, A. As 

 regards the respective functions of animal and vegetable cells, one of the 

 most important differences consists in the power which vegetable cells possess 

 of being able to build up new complicated nitrogenous and non-nitrogenous 



