ELEMENTARY STRUCTURE. 17 



Stage of our inquiries. The more particular description of many 

 of them will be given under the head of Physiology, or, when 

 treating of the plants which yield them, in Systematic Botany. 

 The detailed account of others, again, belongs to Chemistry, and 

 the applications of Botany to Medicine, the Arts, Domestic 

 Economy, and Manufactures. By some authors the term endo- 

 chrome is used to indicate the whole contents of the cell; it is 

 chiefly employed in describing the Algje. We shall tirst describe 

 certain contents which are present more particularly in young 

 cells, and which are actively concerned in their origin and de- 

 velopment, as Avell as in the formation of other substances after- 

 wards contained in them. These are the Protoplasm, Primordial 

 Utricle, and Nucleus. These commonly disappear when the 

 secondary layers begin to be deposited on the walls of the cell. 



Protoplasm. — This substance, which is abundant in all young 

 cells, is a white or yellowish, opaque, viscid fluid, either per- 

 fectly smooth, or of a more or less granular nature. It may be 

 always detected by the application of sugar and sulphuric acid, 

 when it assumes a pink or rose colour. It should be noticed, 

 however, that this colour is frequently not developed for some 

 minutes. Iodine colours it yellow or brown. It is coagulated by 

 acids and alcohol. It contains nitrogen as an essential ingredient, 

 in addition to the three elements — carbon, oxygen, and hydrogen, 

 of which we have seen the primary cell-membrane is alone com- 

 posed. The protoplasm is called by some German writers 

 " schleim,'" and in some Enghsh works " mucus," or " mucilage." 



Primordial Utricle. — When a cell containing protoplasm is 

 placed in Avater, or allowed to remain for some time in alcohol, 

 or is exposed to the action of iodine, the contents separate 

 from the wall (Jig. 34), and are then seen to be bounded by 

 a more or less defined portion of pro- r-- 04 



toplasm having the appearance of a 

 membrane, and which by its contrac- 

 tion has removed all the other con- 

 tents of the cell from its surface. 

 Mohl, who first discovered this struc- 

 ture, and who believed it to possess 

 all the appearances of an inner cell 

 lining the outer one, called it the Pri- 

 mordial Utricle, because this so-called 

 membrane exists previous to the cell- 

 wall formed of cellulose. Whether ^. „, ^ „ , , , . . 



„ I xu i • ^ J i^2£^. 34. Cell of the leaf of 



such an appearance, as that just de- jungermamna Tayiori. 

 scribed, can be considered as owing After Mohi. 



to the presence of a distinct membrane ha\ang the charac- 

 ters of an inner cell, as thus supposed by Mohl; or whether 

 it should not be rather considered as a thin film caused by 

 the coagulation of the surface of the protoplasm by the action 

 c 



