126 



MINUTE STRUCTURE OF THE STEM. 



of the fascicles, and they 

 curve considerably in their 

 course, so that it is often dif- 

 ficult to follow the foliar trace 

 for more than a short dis- 

 tance. If the stem has alter- 

 nate leaves, the direction of 

 the foliar traces will of course 

 be different from that in a 

 stem with opposite or verti- 

 cillate arrangement of the 

 leaves. The following figures 

 exhibit the course and dis- 

 tribution in a few eases : — 

 In the leafy shoot of Clem- 

 atis, Fig. 102, the leaves, are 

 opposite and decussate. From 

 each leaf there descend three 

 fibro-vascular bundles ; for 

 instance, at the lower node 

 there are a, b, c, and e, /, d. 

 The leaves at the node next 

 above decussate with those 

 below ; each of them has 

 three fibro-vascular bundles, 

 respectivelj-, i, gr, I, 

 and k, h, m, which 

 become somewhat 

 smaller as the}' de- 

 scend to the next 

 node, where they be- 

 come blended with 

 the bundles there. 

 An examination of 

 the third node shows 

 that the two leaves 

 there contribute bun- 

 dles to the axial cyl- 

 ■"" inder; there is again 



a blending of the bundles at the node below. 



ai c- 



Fig. 102. Diagrammatic view of a leafy stem of Clematis, showing the arrangement of 

 the fibro-vascular bundles ; a, 6, c, — e, /, rf, the fascicles from the lower pair of leaves ; 

 »i ff) ^ — *i *> ™> tbe fascicles from the second pair of leaves ; g, /■, s, —p, n, <j, the 



