MALE FERN. 347 



(4) The large scalariform vessels, with tapering ends 

 and ladder-like thickening of the side walls. This ap- 

 pearance is due to the very regular transversely elon- 

 gated bordered pits. 



(5) The smaller tracheids of the protoxylem, with 

 spiral fibrous thickenings on their walls. 



(6) The narrow square-ended cells of the endodermis, 

 the pericycle, and the conjunctive parenchyma of the xylem 

 and phloem. 



(7) The large short square-ended or polygonal cells of 

 the general ground tissue, separated by intercellular spaces. 



486. Macerated Tissues of Fern Stem. Cut out 



a few pieces of stem, or longitudinal sections including 

 portions of the vascular skeleton, warm them in a test- 

 tube with nitric acid and potassium chlorate ( 120), rinse 

 in water, and tease out the tissues by means of needles. 

 Examine the macerated tissue, noting the forms of the 

 isolated tissue elements and the markings on their 

 walls, for comparison with their appearance in sections. 



487. T. S. of Root. Cut transverse sections of a root, held in 

 pith. Note 



(1) The piliferous layer, some cells of which grow out to form 

 root-hairs. Remains of these may be seen on the old root, or the 

 hairs themselves may be found on carefully digging up a plant, 

 washing the roots gently to free them from soil, and examining the 

 young tips. 



(2) The thin- walled outer cortex. 



(3) The sclerenchymatous inner cortex, which forms a dense 

 thick ring around the vascular cylinder. The latter is sur- 

 rounded by 



(4) The endodermis, a single layer of rather flattened cells the 

 dot-like markings due to the thickening bands on the radial walls 

 are not easily seen and 



(5) The pericycle, partly single- and partly double -layered. 



(6) Two strands of phloem, one on either side of 



(7) The plate-like strand of xylem, which has the small pro- 

 toxylem elements at either end and is therefore diarch. 



488. Structure of Leaf. Cut transverse sections 

 of barren leaflet, held in pith. Note (1) the upper epi- 

 dermis, a single layer of cells containing chloroplasts ; 



