8o 



BOTANY 



therefore be discussed at any length. The distribution 

 of the conducting tissues is, however, materially different 

 so far as the stem is concerned. The root has its strands 

 placed like those of the dicotyledon, but it never increases 

 in thickness and does not show, therefore, any develop- 

 ment of cambium or secondary woody elements. The 

 strands in the stem are confined to the central cylinder, 

 but each conjoint strand of bast and wood passes up the 



stem separately. Each is 

 surrounded by a protecting 

 sheath of hardened cells 

 and never contains any 

 cambium. The strands 

 are numerous and are 

 arranged in a series of 

 circles. When the number 

 is very great this circular 

 arrangement cannot easily 

 be seen and the strands 

 appear to be scattered 

 thickly through the central 

 cylinder (Fig. 36). They 

 are found to be continuous 

 with similar strands in the leaf, which as before are called 

 the veins. These run in the main parallel to one another, 

 and do not form the complex network which is seen in 

 the leaf of a dicotyledon. 



The relations of the leaf to the stem are a little 

 different from those of most dicotyledons. The bases of 

 the leaves sheathe the stem and do not as a rule fall off 

 in autumn. The leaf, however, sooner or later dies, but 

 its base remains where it was. As the stem grows 

 older, as in the case of many palms, these leaf bases 

 cover nearly the whole of the trunk, causing the latter 

 to appear much thicker than it really is. 



The leaf has palissade parenchyma in a narrow layer 

 under both surfaces. 



FIG. 36. Diagram of transverse sec- 

 tion of stem of monocotyledon. 



