ELEMENTARY ORGANS. 



CHAPTER I. 



ELEMENTARY ORGANS. 



5. Vegetables are composed of solids and fluids. There 

 are three solids : an extremely delicate elementary membrane, 

 elementary fiber of extreme fineness, and organic mucus. From 

 one or all of these are formed several classes of tissue^ which 

 make up all vegetable structures. 



6. Membrane is certainly the most important of the three 

 primitive conditions of vegetable substance. It enters into the 

 composition of all the various tissues, and no doubt forms the 

 great mass of vegetables. With respect to the constitution of veg- 

 etable membrane, two opinions have been held : one, that it is an 

 inorganic substance, destitute of fibers, like the fine film composing 

 a soap bubble ; another, that it is organized. The chemical con- 

 stitution of membrane is almost identical with starch, into which 

 it is readily transformed. It is called cellulose. Membrane, in its 

 early stage, is extremely thin, but becomes thick by the deposition 

 of other matter. It is entirely destitute of visible pores ; never- 

 theless, it is permeable to fluids under certain circumstances. 

 Pores have been described as existing in the membrane, as it 

 composes the tissues, but they have more recently been shown 

 to be an optical illusion : the apparent pores being pits within 

 the membrane, making some parts transparent and thinner than 

 others. That this is the case, has been proved by the chemical 

 action of substances making the membrane opake, when the 

 pores ceased to be discoverable, and all the membrane became 

 of a uniform appearance. 



7. Elementary Fiber exists in various parts of plants, usually 

 united with membranous vessels, and generally assuming a 

 spiral direction. Most botanists consider it a simple, solid fiber. 

 Its extreme fineness would lead us to this opinion, since the 

 largest kind does not exceed 7 q 00 of an inch. It is not 

 always coiled ; sometimes it is straight, at others curved, and 

 sometimes forming a single line ; at others anastomosing, and 

 forming a reticulated tissue, and at others, branching. It in- 



5. Of what arc vegetables composed ? How many solids ? What arc they ? 

 "What are formed of these ? — 6. Which is the most important? What does 

 it form ? What is the chemical constitution of membrane? Its state in 

 its earliest stage ? Has it any pores ? Is it permeable to fluids ?— 7. Where 

 does elementary fiber exist? In what forms ? 



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