60 



MORPHOLOGY OF THE CELL. 



2. Vessels, or ducts. 



a. Dotted. 



b. Spirally marked. 



c. Annular. 



d. Reticulated. 



e. Trabecular. 



3. Bast-cells, Bast-fibres, or Liber-fibres. 



III. Sieve-cells, or Cribrose-cells. 



IV. Latex-cells. 



Intercellular spaces and canals are neither cells nor tissues, 

 but they require consideration in connection with them. 



I. Cells of the Fundamental System, Parenchyma in the -widest 

 sense, including Modifications for Protective Surfaces. 



PARENCHYMA. 



203. This term is applied at present to all t}'pical cellular 

 tissue except that which belongs to the epidermal system. It 



therefore constitutes 

 the mass which sur- 

 rounds fibro-vascu- 

 lar bundles, forming 

 pith, medullary rays, 

 the pulp of leaves 

 and fruits, etc. It 

 occurs in nearly all 

 parts of all plants. 



The elements of 

 parenchyma are sim- 

 ple cells more or less 

 separable from each 

 other, in some cases 

 by slight pressure, 

 and in others by the 

 cautious use of a 

 macerating solution. 



The cells vary greath' in form, but usually are polyhedral or 

 spheroidal. Extended classifications of the cells themselves, 

 based upon form, have been made, but they are of no utilit}- 

 and of small historical interest. Yet three principal shapes ma}' 

 well be distinguished ; namely, short or isodiametric, elongated, 

 and flattened. 



FIG. 37. Parenchyma from stem of Marrubium. 4. (Jacobs.) 



