Metaphyta L ilium. 



but differing in certain points of detail The tissue of the 

 strand is confluent with the fundamental parenchyma, but 

 the cells bounding the strand are much smaller and thicker 

 walled: these cells are elongated and form a prosenchy- 

 matous sheath to the strand. Towards the outer side of the 

 strand, i.e. that next the surface of the stem, immediately 



FIG. 65. MOXOCOTYLEDONOUS STEM, (Maout and Decaisne.) 



A. Diagrammatic transverse section. 



B. Diagrammatic longitudinal section. 



inside the prosenchymatous sheath, 

 is found a mass of tissue which cor- 

 responds to the phloem or bast of 

 the fern strand, and goes by that 

 name. It consists of sieve-tubes, 

 long, thick- walled prosenchymaand 

 thin-walled parenchyma. Next the 

 inner side of the strand lies the 

 xylem, or wood, which also consists 



of three elements, tracheides, or vessels with dotted walls, 

 one or more spiral and annular vessels, a quantity of pro- 

 senchyma, and a little parenchyma. We have already 

 briefly glanced at the general structure of the cells compos- 

 ing these several types of tissue. As we shall, however, 

 require to use these terms constantly in the remainder of 

 this and in the succeeding sections it may be well to give 

 at this point a few more details regarding them. 



L 2 



