SECT. I 



MORPHOLOGY 



125 



In the stems of Monocotyledons (Fig. 127) the vascular bundles 

 are scattered, and without any apparent regular order. Their 

 scattered arrangement is due to the varying distances to which the 

 bundles of the leaf-traces penetrate into the central cylinder of the 

 stem. This results from the prolonged growth in thickness of the 

 growing point after the procambial strands have been laid down ( 12 ). 

 A common arrangement of the bundles in monocotyledonous stems is 

 that of the so-called Palm type, in which each leaf-trace consists of 



FIG. 134. Diagram showing the course of the vascular bundles in a shoot of Taius Imccvtv. 



the numerous bundles which pass singly into the stem from the broad 

 leaf-base. The median bundle penetrates to the middle of the stem. 

 The depth to which the lateral bundles penetrate varies with their 

 remoteness from the median bundle. In their descending course the 

 bundles gradually curve outwards, and finally join other bundles 

 near the periphery of the stem. The number of internodes, therefore, 

 through which a bundle passes before coalescence, is variable ; the 

 median bundle, however, continues distinct for the longest distance. 

 The deeper penetration and greater length of the median bundle 

 become apparent in a median longitudinal section of such a stem 



