16 



PLATE Vni. 



HISTOLOGY OF FLOWEEING PLANT. 



Stf.m — 



JJiAG. 1. Transveese Section of a one-year-old stem of Horse Chestnut — 

 Pith or medulla in centre. 



Fihro-vascular Inmdles arranged in a ring round the jiith — ■ 

 Wood or xylem, including medullary sheath. 

 Cambium, a soft cellular layer. 

 East or phlcEm outside the cambium. 

 Cortex, connected with the pitli by the medullary rays. 

 Epidermis. 



Note. — The part of the stem outside the soft cambium is readily removahle, and is the separable bark. 



Fig. 1. Transverse Section of same stem under the microscope — 

 Pith, consisting of parenchyma cells. 

 Fibro-vasciilar bundle — 

 Wood or xylem — 



Vessels, large openings. 

 Wood-cells between the vessels. 

 Cambium, small tliin-walled cells. 

 Bast or phloem — 



Soft portion, made up of thin-walled cells. 



Hard portion, or liber layer, made up of round thick-walled cells, the cewtral cavity 

 being almost obliterated. 

 Medullary rays, brick-shaped cells between the fibro-vascular bundles. 

 Cortex, angular cells, parenchyma. 

 Epidermis, a single layer of squarish cells. 

 Fig. 2. Long. Section of the Horse Chestnut stem — 

 Pith-cells. 



Fibro vascular bundle — 

 Wood- 

 Spiral vessels of medullary sheath, elongated tubes with spirally thickened walls. 

 Annular vessels, elongated tubes with ringlike thickenings. 

 Potted ducts, elongated tubes thickened so as to leave thin places, the dots. 

 Wood-cells, elongated, and when older with thick walls, and then called woody 

 fibres or wood prosenchj'ma. 

 Cambium, thiu-walled cells. 

 Bast- 

 Soft bast, elongated thin-walled cells. 



Hard bast, thick-walled and elongated cells forming the flexible bast fibres. 

 Cortex, parenchymatous cells. 

 Epidermis, a single layer of cells. 

 Figs. 3, L Sections of stem of Butcher's Broom magnified — 

 Differences from Horse Cliestnut stem — 



Fibro-vascular bundles are not arranged in a ring round pith, but scattered irregu- 

 larly. 

 Xo cambium and therefore no provision for increase after first year. 



