the Nitrogenous Matter of Plants, 37 



liquid and by the abundance of nitrogenous granules contained 

 within the membraniform envelope. 



Hitherto the nucleus has been referred to as a nearly spherical 

 globule ; however, this form is not always that which it presents, 

 although it is the most widely met with when the liquid it con- 

 tains completely fills it, which happens in those portions of plants 

 which are gorged with a large quantity of water; but when its 

 cavity is less full, or when it is in motion, it has sometimes a 

 wrinkled appearance (as in Erodium moschatum), and at others a 

 WTinkled and tuberculated appearance at once {Salvia Sclarea), 

 and is very irregular in its outline. 



With regard to the dimensions the nucleus may attain, there 

 is great variety ; but in general it bears a pretty direct relation 

 to the size of the cells when these have attained their complete 

 growth, or a little before that period. Thus it is that the nucleus 

 is found highly developed in the Liliacese, Commelinese, the 

 Orchidacese, Cactacese, Crassulacese, Aroidese,' in most Cheno- 

 podiese and Solanese, and in the fleshy parts of all plants, such as 

 the fruit of Rosacese, Rhamnese, Ampelidse, Grossulariacese, &c., 

 which generally exhibit cells of large volume. On the other 

 hand, it is small in most Graminese, Apocynese, Amentacese, and 

 Jasminese, whose cells are commonly small in size. 



The volume of the nucleus, compared with that of the cell, 

 when young, is proportionally very great, as may be seen in 

 the epidermis of the unexpanded flower oi Helleborus niger, or in 

 the young merithalli, spongioles, leaves, flowers, and pollen in 

 course of growth; for in such examples the dimensions of the 

 nucleus are so considerable that it sometimes occupies one-fourth 

 of the whole of the cell-cavity. But when the cell has attained 

 its full development, it is adherent to it, and occupies a far 

 smaller proportional space within it than heretofore, being then 

 reduced to one-tenth, one-fifteenth part, or even less of its cavity. 

 However, though the nucleus itself does not keep pace with the 

 growth of the cell, we shall find that, in the subsequent modifica- 

 tions it soon undergoes, it will, by means of appendages given off 

 from it, acquire an equal increase with the cell, and a degree of 

 development proportionate to the extent of its walls. 



When examined relative to its consistence, the nucleus is found 

 to be soft and extensible ; sometimes, when distended by its con- 

 tained liquid, it is ruptured in the attempt to detach by a sudden 

 pull the small lamina of tissue to be submitted to examination. 

 Its surface may be smooth, tuberculated, or wrinkled — varieties 

 of appearance of which we shall presently recognize the cause. 

 Lastly, it is not unusual to see it bordered by little vesicles; but 

 these by degrees decrease in size under the eye of the observer, 

 and ultimately merge into it. 



