THE STRUCTURE OF THE STEM 



369 



bundle is surrounded by a sheath consisting of a few layers of 

 sclerenohyma belongmg to the conjunctive tissue of the stele. 



Viewed in longitudinal section the bundles are seen, as m 

 the other type, to be common bundles, being continuous with 

 those which belong to the leaves. Usually there are several 

 bundles in each leaf. Each can be traced inwards for some dis- 



FlGf. 754. 



Fig. 755. 



\ 



: — pe. 



[•"i'l. 753. Diagrum of course of bundles in the sbem oi 



a Monocotyledon (Palm). Fig. 76 (. Diagram of 



modP. of growth of stem of Monocotyledon ( Zea MaU). 



After Sachs. Fiff. 755. Part of a section of stem 



of Dracwna. pe. Cork. co. Cortex, m. Cambium 

 layer. 6, b. Bundles in course of formation. 



tance, after which its course gradually curves outwards, proceed- 

 ing obliquely down the stem; it ultimately joins a bundle origi- 

 nating from a lower leaf (fig. 753). 



In most grasses, in consequence of the great and rapid elon- 

 gation of the internodes, the bundles appear to lie perpendicu- 

 larly in the stem. They do not extend far towards the centre 

 of the stele, which becomes hollow. At the nodes the bundles 



VOL. I. B B 



