BOTANY, 



ELEMENTARY ORGANS 



SIMPLE ORGANS. CELLS AND VESSELS. 



Cells, or Cellular Tissue. 

 An assemblage of cells joined together, composed each of a 

 spherical dodecaedric fusiform sac, generally from one-three- 

 hundredths to one-five-hundred ths of an inch in diameter; 

 membrane of the sac fine, delicate, imperforate, and most fre- 

 quently marked with dots ; colour green, owing to the interior 

 globules. The cellular tissue, which is the general, and 

 sometimes the sole element of plants, increases by the deve- 

 lopment of new cells, either in the intervals, or, in some cases, 

 in the interior of the old ones. 



Vessels. 

 Trachea. 



Each a tube formed by a spiral thread which may be un- 

 rolled in the form of a corkscrew, and included in a membrane, 

 as if it had been born in a cell ; form cylindrical ; diameter 

 from one-three-hundredths to one-three-thou sandths of an inch ; 

 extremities conical. They are found in all the organs of vas- 

 cular plants, the leaves of flowers, &c, principally around the 

 pith of dicotyledonous trees. 



Annular, or Radiated Vessels. 



Cylindrical tubes, not ramified, marked with regular trans- 

 versal rays, parallel with each other, not susceptible of being 

 unrolled, sometimes very close together, and, owing to the 

 presence of veritable solid rings, fixed at variable distances 

 from one vessel to another, but at equal distances in the same 

 vessel; diameter the same as in the tracheae. 



