oOO Vegetable Physiology. 



The circulating movement of the protoplasm in the interior of 

 cells is observed in many young cells, and may perhaps be uni- 

 versal in early stages of growth ; but in most nascent tissues it is 

 difficult to get an observation without injuring the structures so 

 much as to disturb the internal economy of the cell, through 

 endosmotic or exosmotic actions. It may be seen very well, 

 however, in young hairs of Flowering plants, which, projecting 

 from the epidermis of organs, may be examined without the 

 necessity of dissection. In these the movement is seen in the 

 protoplasm lining the walls, and in addition, the viscid threads^ 

 which run across the cavity and connect the nucleus with the 

 primordial utricle move about, change their form, and carry along 

 the nucleus with them. The protoplasm is usually almost 

 colourless in these cases, and the motion is only rendered visible 

 by the presence of minute granular matter which always exists in 

 the protoplasm. These movements cease very early in plants 

 growing in air, but they persist in the cells of many water-plants, 

 where the movement may be seen not only in the transparent 

 young organs, but in sections of the full-grown leaves, c^c, where 

 the presence of chlorophyll-granules above referred to renders the 

 movement very evident. 



It has already been shown how important the protoplasmic 

 cell-contents are in reference to the formation of cells (vol. xvii. 

 p. 78 et seq.)^ and we shall have presently to direct attention 

 to the evidence of their agency in producing the various other 

 substances which are met with in living cells. But protoplasmic 

 substances are not only accumulated in the cells for the purposes 

 of reproduction or nutrition of the individual cell in which they 

 occur ; we find tissues in what we may term the " resting" 

 structures of plants, wherein the cells are loaded with a store of 

 protoplasmic matter to serve as material for future wants. This 

 is especially the case in seeds, buds, bulbs, tubers, and the like. 

 The outer layers of the cells of the endosperm of the corn grains, 

 beneath the hard skin, and the cells in the vicinity of the embryo, 

 contain no starch, but are filled with protoplasmic nitrogenous 

 matters in the form of globules or granules of semifluid consist- 

 ence (fig. 11). A small quantity of this same substance exists 

 with the starch in the inner cells. A portion of the cells of the 

 embryo of beans (fig. 2) and pease exhibits a similar character, and 

 this accumulation of assimilated nitrogenous matter is a constant 

 phenomenon in seeds. As will be shown hereafter, this matter is 

 removed from the cells and consumed by the young plant during 

 germination. 



None of the substances met with in the contents of cells have 

 greater claim to the attention of the physiologist than cldorophyll, 



