12 PEOPAGATIOlir OF PLANTS. 



ticulturists are compelled to confine themselves to seek- 

 ing a knowledge of the best means of promoting the 

 development and multiplication of the cells, which, in 

 their aggregate form, compose the plants that contribute 

 so much to the welfare and pleasure of all members of 

 the animal kingdom, man included. 



The plant-cell, however minute, is not a solid body, nor ^ 

 composed of a single element, but in structure is made 

 up of several parts, and these are the result of a combina- 

 tion of several substances. Within the young cell we 

 find a viscid liquid, which has received the name oi proto- 

 plasm (meaning formative matter), and usually floating in 

 this there are numerous granules, the nature of which has 

 not been fully determined, but they are supposed to be a 

 kind of cell-kernels or nuclei, that probably play an im- 

 portant part in the production of new cells. As the cell 

 acquires age and enlarges, the protoplasm forms a gela- 

 tinous coating on the inside of the true cell membrane, 

 or what may be considered the proper wall of the cell. 

 This membraneous inner surface of the cell-wall is called 

 the internal utricle by Mulder, and primordial utricle 

 by Mohl. It is only visible in new and very young cells, 

 and soon disappears; but, when present, maybe detected 

 under the action of a tincture of iodine, which turns it 

 yellow. As the cells thicken the internal utricle, also 

 the cell-kernels or grannies, become incorporated with the 

 cell-walls. The chemical composition of the complete 

 or mature cell is made up of three elements, carbon, 

 hydrogen and oxygen; but in this young and immature 

 state the protoplasm contains nitrogen, and the nitrogen- 

 ous substances are known undei* various names, such as 

 gluten, albumen, and other well-known products of veg- 

 etables. 



Commencing with the individual cell, we find them in 

 a vast number of plants so minute that they are invisible 

 to the unaided eye, and their forms can only be deter- 



