PRACTICAL BOTANY 



Runner, taking care here also to avoid the base of the 

 hypocotyledonary stem, and treat as before. Observe 



1. Centrally a parenchymatous pith. 



2. The primary xylem groups, usually four in number, 

 retain their original position, relatively to the pith. 



3. Four large wedges of secondary xylem have originated 

 internally from the four cambium zones. These are separated 

 from one another laterally by 



4. Four broad parenchymatous rays, which lie on the same 

 radii as the primary xylem. Outside the xylem is 



5. The cambium, having similar characters to that of the 

 stem, and giving rise peripherally to 



6. Secondary phloem. Note if possible 



7. The four groups of primary phloem now separated from 

 the primary xylem, but still on radii alternating with the latter. 

 The section is bounded by 



8. A narrow band of cork with a cork-cambium at its inner 

 limit : this originates from the pericycle, and this point should 

 be ascertained by cutting sections successive ly at older points. 

 It is to be noted that the endodermis, cortex, and 

 piliferous layer, are absent in these sections, these being 

 thrown off on the formation of the layer of cork from the 

 pericycle beneath them, which thus cuts them off from a 

 physiological connection with the central cylinder. (Compare 

 Fig. 8, p. 91.) 



ii. Ligneous Type. 



For comparison with the root of Phaseolus, which is charac- 

 teristic rather of that of herbaceous plants, observations should 

 also be made on the roots of some woody plant. The root of 

 the Elm has its cortex densely crowded with mucilage-cells, 

 and in other respects is not very suitable for work : the Horse- 

 Chestnut (./Esculus Hippocastanum) is a better type of a root 

 of an arboreous plant. Dig up roots of ttiis plant carefully so 

 as not to break off the finer fibrils : wash them gently from the 

 soil, and observe the reddish-brown colour of the thicker and 

 more mature parts, while the ends of the thinner fibrils are 

 pale-coloured. Note also on passing from young portions to 



