SKETCH OF THE RUDIMENTS OF BOTANY. 



ELEMENTARY ORGANS. 



1. The tissue of which plants consist, appears under four forms, 

 viz : cellular tissue, woody fibre, spiral vessels, and ducts. These are 

 called elementary organs. 



2. Cellular Tissue or parenchyma is composed of transparent vescicles, 

 variously cohering with each other. It is the only form universally 

 found in plants ; the other forms being often partially or entirely want- 

 ing. 



3. Woody Fibre is a tissue consisting of elongated tubes, similar to 

 the vescicles of cellular tissue, and is therefore often called elongated 

 cellular tissue. 



4. Spiral Vessels are formed of elastic tissue, twisted spirally into 

 the form of a cylinder, and capable of being unrolled. They only 

 exist in plants propogated by stamens and pistils, and hence the 

 two primary divisions of the vegetable kingdom into Vasculares and 

 Gellulares. 



.5. Ducts are elongated, transparent tubes, composed of tissue that 

 is not capable of unrolling. 



6. All these forms are covered by a membrane called the cuticle. 



7. From peculiar combinations of the elementary organs are formed 

 the compound organs. 



8. The root is formed by the descending and dividing fibres of the 

 stem ; and by it plants are with few exceptions fixed to the earth, and 

 nutriment absorbed. 



9. It is distinguished from the stem by the absence of leaves, of pith 

 even in those plants in which it is abundant in the stem, and of spiral 

 vessels. 



10. It usually consists of three parts ; the neck, (collum) or line of 

 separation from the stem ; the body or middle portion ; and the fibres 

 or little roots, through which the nourishment is principally derived. 



11. The following are the principal kinds of roots : 



a. Conical, or principal tap root as it is sometimes called ; tapering 

 downwards and emitting fibres from various parts of its surface ; as in 

 the carrot. 



b. Fusiform, when the conical root is attenuated towards the neck, 

 as well as below ; as in the radish. 



c. Napiform, when it is swollen out extremely in the upper part and 

 suddenly attenuated below ; as in the turnip. 



d. Abrupt, when the fusiform root is as it were cut off suddenly. 



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