602 THE WONDERS OF GEOLOGY. Lect. VI. 



the granules escape, and float in the water till they 

 become fixed to some other body ; they then reproduce 

 cells, which are aggregated after the same pattern as in the 

 parent plant. The common mould or mustiness is a cluster 

 of plants formed of cells only ; and there are some vegeta- 

 bles in which the entire plant consists of but one isolated 

 cell; such are the yeast fungus {Tortula cerevisice), and the 

 red snow (Leparia nivalis). In these examples we see that 

 all the functions of vegetable life, namely, absorption, assi- 

 milation, the fixation of carbon from the atmosphere, re- 

 spiration, exhalation, secretion, and reproduction, are effected 

 by one single cell. Even in the highest and most compli- 

 cated orders of vegetables, in which there is a variety of 

 organs adapted for the performance of different offices, these 

 functions are effected by the agency of cells, which obtain 

 materials of formation and support from the ordinary 

 chemical agents around them. Thus an aggregation of 

 simple cells forms the cellular tissue : a fusion or blending 

 of several cells produces the vessels, and so forth ; and by 

 cells are elaborated the gum, resin, oil, starch, gluten, &c : 

 and by cells specially endowed, are secreted the narcotic 

 of the poppy, the deadly poison of the nightshade, and the 

 stimulant aromatic of the clove. 



In like manner, in animal structures, all the various 

 processes of vitality are performed by cells or globules, 

 varying in size from infinite minuteness to forms visible to 

 the unassisted eye. Thus one system of cells secretes the 

 bile, another the adipose substance, another the nervous 

 matter, and so forth ; but how these special products are 

 formed by cells apparently of similar organization we know 

 not. Whether the special endowment belonging to the 

 system of cells of a particular organ depends on the 

 intimate structure of the wall or tissue of such cells, and 

 this structure be so attenuated and infinitesimal as to elude 

 our observation ; or whether it results from the transmission 



