CORTEX. 



[CH. IV 



suffice to know that the cells to which it gives origin in 

 Helianthus go to form fibrous and vascular elements which 

 partly fill up the spaces between the original bundles. 



Cortex. 



The points to be noticed in the cortex are not many. 

 Under the single layer of epidermis are several layers 

 of cells of which the walls are thickened in such a way as 

 to give a certain clumsy look to the outline, and which 

 have moreover a peculiar gloss or sheen. 



These two characters, the glistening texture and the 

 peculiar thickening of the walls, are common to tissue of 

 this kind, which is known as collenchyma. 



FIG. 27. 



TBANSVERSE SECTION THROUGH A KIDGE ON THE STEM OF CLEMATIS. 

 Beneath the epidermis the section shows a mass of collenchyma remark- 

 able for the thick walls separating adjacent cells : the protoplasmic 

 contents have fallen out of many of the cells. 



Lastly, the cortex contains running through it a 

 number of ducts or tubes known, from the nature of their 

 contents, as resin ducts. In transverse section a duct 

 appears as a space surrounded by a rosette of 5 or 6 

 cells. The physiology of resin ducts is obscure and need 

 not be discussed. 



