74 MORPHOLOGY AND LIFE HISTORY 



network? Is there any connection between 

 the cell-cavities of adjacent cells? 



(d) In a similar manner examine the cellular struc- 

 ture of the hypodermal sclerenchyma. 

 (e) Make drawings illustrating the features ob- 

 served in (c) and (d), showing four cells of the 

 epidermis, and three or four of the underlying 

 sclerenchy ma-cells. The cells should not be 

 less than 10 to 15 mm. in diameter. 



(/) Make similar studies and drawings of the cells 

 of the parenchyma. 



(g) Study one of the smaller fibro- vascular bundles 

 and distinguish, from the circumference toward 

 the center: 



(1) The outer bundle-sheath, or endodermis. 



(2) Within the endodermis, and adjacent to it, 

 a single layer of starch-bearing parenchy- 

 matous cells, the phloem-sheath. 



(3) Thick- walled bast-fibers. 



(4) Larger, thin-walled cells, having their cell- 

 walls perforated, the sieve-tubes. 



(5) Associated with the cells mentioned in 

 (2)-(4), parenchyma-cells (phloem-paren- 

 chyma), containing starch. 



(6) The cells mentioned in (3)-(5) constitute 

 the phloem-region, of the bundle, or 

 phloem. 



(7) Within the phloem is the xylem-region, or 

 xylem, composed of 



(8) Large, conspicuous tracheids, whose walls 

 have ladder-like (scalariform) markings, as 

 seen in longitudinal section. Each tra- 

 cheid is formed from a single, elongate, 

 tapering cell; the living matter, or proto- 



