COURSE OF BUNDLES IN THE STEM. 



237 



Ueris amara (Figs. 92,93), foliage shoot. The arrangement of leaves in the terminal bud 

 is ^. Each bundle descends through 10 or 11, rarely 12, internodes and inserts itself 

 there on that of the 5th lower leaf. Meanwhile it describes the form of an elongated S, 

 since it bends from the vertical, first to the ascending or anodic side of the leaf-spiral, 

 then to the descending or kathodic 

 side in a tangential direction. The 

 bundles thus run separately through 

 5, 6, or 7 internodes. By their coale- 

 scence there are formed 5 sympodial 

 bundles, which traverse the whole 

 stem : these complete a circuit in 65 

 internodes, while the separate bundles 

 appear as one-sided branches from 

 them. The oblique course of the leaf- 

 traces is contrary in direction to the 

 leaf-spiral ; i.e. if the latter were right- 

 handed, the bundles would curve up- 

 wards towards the left. Oblique con- 

 necting bundles appear later between 

 the leaf-traces, originating in the 

 1 4- 1 8th internode which has vascular 

 bundles. 



To this type belong further Arabis 

 albida, Jasminum fruticans, Sarotham- 

 nns scoparius (comp. Nageli, Han- 

 stein, I.e.). 



2. Leai'es spirally arranged. Leaf- 

 trace of more than one bundle, pectinat- 

 ing at most ivith the fifth trace beloiv. 

 Several (3 or 5) bundles go from 

 one leaf through the stem, and unite 

 sooner or later with one another. 

 These pectinate with the trace of 

 the fifth or a still lower leaf. 



Lepidium sativum. The cotyledons 

 and the two succeeding almost oppo- 

 site primordial leaves have traces 

 with a single bundle. Of the later 

 leaves, which are all arranged spirally, 

 some few of the first have 3 bundles, 

 one strong median bundle, and two 

 weaker later ones, which unite im- 

 mediately on entering the stem. In 

 all the later leaves the median bundle 

 is divided into 3. At the point of 

 transition from stem to leafs bundles 

 are seen, of which the median ones 

 are formed first, the two marginal 

 ones last. The 3 median bundles 

 are rather stronger, and unite above 

 to form the median bundle of the 

 leaf. Below, they separate from one 

 another, and the 2 weaker marginal 

 bundles unite with them, so that the leaf-trace now descends through the stetn as three 



Fig', 92. 



FiS- 93- 



Figs. 92, 93.— Iberis aiiiara, after Nageli. Fig. 92. Scheme of the 

 course of the bundles in the young foliage shoot ; the ring of bundles 

 spread out in a vertical plane. The figures indicate the successive 

 bundles of the leaf-trace at their point of exit from the ring into the leaf. 

 ~-F>S- 93 {'5)- Transverse section through tiie internode above the point 

 of exit of bundle 5 ; meaning of figures as in Fig 92. 



