PLANT DEVELOPMENT. 21 



B. Cellulose, or cell-fabric. This consists chiefly of car- 

 bon and water; it makes the fabric of all plants. This 

 wall surrounds an inelastic jelly-like substance (from which 

 it is separable) called 



C. Protoplasm, or First mould (Gr. protos, first, plasma, 

 mould). Protoplasm consists chiefly of carbon, water, and 

 nitrogen, the elements that form animal fabric. It has the 

 inherent power to move in every direction toward inorganic 

 substances; to convert them into organic matter; and to 

 transmit to this organic matter its own powers of digestion, 

 growth, and reproduction. It is a homogeneous mass, usu- 

 ally globular; its periphery, or limiting surface, — called 

 the film, — is slightly firmer than the rest of the mass of 

 protoplasm ; but it is exactly identical with it, and insepa- 

 rable from it, and may be compared to the surface of a drop 

 of water, or of a mass of fresh jelly. This protoplasm — 

 of course including its film — is sometimes called 



D. Primordial utricle, or First-bladder, — a name given 

 it by Mohl, — because it is the first-formed part of every 

 organism, whether vegetal or animal. We have already 

 seen it in the embryonic vesicle of the higher plants (Fig. 

 3, A). A denser portion near the centre of the mass is 

 called the nucleus; it is the seat. of vital activity. Within 

 the nucleus there is often to be seen a well-defined spot 

 with the vitality almost of an eye; this is called the 

 nucleolus, or little nucleus. 



Protoplasm is the first beginning of every cell. It builds 

 itself, out of itself; it next constructs, out of its own ma- 

 terials, the cellulose, which is the wall of its house ; which is 

 separable from it ; and which completes the vegetal cell. 



"We find all the elements of protoplasm in inorganic nature. "We 

 combine them in the exact proportions in which they exist in the 

 living cell ; but we cannot make protoplasm. Nor is it ever free in 

 nature. It is always pre-existent in a mother-cell, or in a wandering 

 mass called Plasmodium, as in the slime-moulds (53). Farther than 

 this we cannot go. The most daring explorer is arrested here, at the 

 threshold of life, by this silent door-keeper. "We can no more tell 

 whence came this first living mother than we can tell whence came the 

 first inorganic atom. 



38. Digestion and Growth. — We watch one of these 

 little plants (which are usually associated in masses). It 



