XIV.] LIVING MATTER AND ITS EFFECTS. 221 



it is called a nucleated cell. The protoplasm contains the 

 protein compounds, and the larger proportion of the saline 

 and watery constituents of the plant. The cell-wall is mainly 

 cellulose and water. Saccharine and fatty matters probably 

 exist, diffused through the protoplasm, in all the cells; starch, 

 in the form of granules, is to be found in most. 



The embryonic pea-plant, then, is no simple homogeneous 

 mass, but is an aggregate, made up of a muldtude of distinct 

 nucleated cells, each of which is essentially composed of a 

 protoplasmic body invested by a cell- wall. The fact that 

 this cell-aggregate is alive, does not become manifest until 

 the pea is exposed to certain conditions. But, every one 

 knows, that if a pea is planted in the ground in moist and 

 warm weather, it shortly bursts its coat. The seed-leaves 

 enlarge and come to the surface ; while the rootlet grows 

 into the soil. The stem shoots up; its minute and colourless 

 leaves rapidly enlarge and become green ; new leaves are 

 developed ; and, by degrees, a tall plant rises above the 

 ground, the bulk and weight of which soon becomes many 

 thousand times greater than that of the embryo. Then the 

 plant blossoms, and in the centre of each flower is found a 

 hollow organ, the pistil. From the walls of this, small 

 bodies termed the ovules grow out, and each ovule contains 

 a microscopic nucleated cell — the ettibryo cell. In the fer- 

 tilised ovules, the embryo cell divides and subdivides, each 

 new cell growing until it becomes as large as, or larger than, 

 that from, which it. proceeded ; and, thus, by degrees, the 

 single cell is converted into a cell-aggregate, which assumes 

 the shape of the embryo plant. This, inclosed in the dis- 

 tended envelope furnished by the ovule, is the pea — while 

 the enlarged pistil becomes the peascod. 



Thus, the plant under consideration goes through a series 

 of changes, the starting-point of which is the simple nucleated 



