154 



STRUCTURAL BOTANY 



We see that each bundle on entering the stem from a 

 leaf (I) passes very gradually inwards, until it is only 

 a short distance from the middle of the stem. It then 

 turns straight down, and at last joins on to a bundle 

 which starts from a lower leaf. Now, this course is 

 not essentially different from what 

 we found in the Wallflower. The 

 great difference in the transverse 

 section depends on the fact that 

 the. bundles pass very gradually 

 inwards, so that when we cut the 

 stem across, our section passes 

 through a number of them at 

 various points of their inward 

 course. Thus the small outer 

 bundles (Fig. 57, & 3 ) in the 

 transverse section are those which 

 are nearest the leaf and have only 

 just entered the cylinder. (The 

 outline of the cylinder is indicated 

 by dotted lines in the diagram, 

 Fig. 58.) The intermediate bundles 

 (& 2 ) are cut through at a point 

 nearer the interior; while the 

 largest (b^ are those which have 

 approached nearest to the centre 

 of the stem and have turned straight down. 



In the bulb the course is still more complicated, for 

 here each bundle first bends in towards the middle and 

 then out again, and only joins on to other bundles near 

 the outside of the stem (see lower part of Fig. 58). 



FIG. 58. Diagram to 

 show course of the 

 bundles in the flower- 

 ing stem and bulb of 

 the Lilies, as seen in 

 longitudinal section. 

 Z, insertion of a foliage 

 leaf; s, insertion of 

 a bulb -scale. (After 

 Falkenberg. ) 



