MALE FERN. 



345 



(a) With the low power note (1) the epidermis, a 

 single layer of narrow cells with thick dark-brown outer 

 walls ; (2) the scale-hairs, each consisting of a single- 

 layered plate of cells arising from the epidermis ; (3) the 

 sclerenchyma, a band of compact tissue with thick 

 yellow lignified and pitted walls, separated by (4) a layer 

 of compact outer parenchyma with thick but colourless 

 walls from (5) the large central parenchyma in which 



Fig. 84. FERN. 



Part of Transverse Section of Stem, showing 

 two of the Vascular Strands. 



(6) the vascular bundles are embedded. The tissues 3, 

 4, and 5 constitute the ground tissue ; in 5 the cells are 

 separated by intercellular spaces (in which short glandular 

 hairs sometimes occur), have thin pitted cellulose walls, 

 and contain abundant starch grains. 



(fe) In a single vascular bundle, note (1) the sharply 

 marked endodermis, consisting of a single layer of narrow 

 cells with thick brown or yellow walls, surrounding the 

 proper vascular tissue ; the latter consisting of (2) 

 pericycle, usually a single layer at the two ends of the 

 bundle and a double layer at the sides, its cells polygonal 

 with cellulose walls and starchy as well as protoplasmic 

 contents ; (3) phloem, surrounding (4) the xylem which 

 occupies the centre of the bundle. The phloem consists of 

 sieve-tubes, polygonal in cross section, apparently empty 



