174 



THE MARATTIALES 



leaf traces with these takes place exactly as in the younger plant. Fig. 157, B, shows 

 the separate leaf traces and the free axial strand, while in A the leaf traces are 

 becoming fused with the broad central strands and the axial strand is also anastomos- 

 ing with one of the latter. This has taken place at the point of junction with a 

 root. While in the younger sporophyte the mucilage ducts are confined to the central 

 region, in the older plant they occur also in the peripheral region of the stem (fig. 

 157, m). The details of the vascular bundles are shown in figs. 158 and 159. 



B Q 



Fig. 158. — Details of vascular bundles from sections shown in fig. 156. 

 A and B are the ends of the crescentic bundle shown in fig. 156, D ; C, is a leaf trace and D part of an older bundle. X l 



SO. 



To recapitulate: The vascular system in the young sporophyte of Dancea 

 begins as a single axial strand, which is continuous through the cotyledon and root. 

 At a very early period a second vascular bundle or stele is formed in the second leaf 

 connecting with the primary strand, and this is followed by a similar single strand 

 or stele in each succeeding leaf, up to about the seventh. Up to this time, except 

 for the steles of the secondary roots, the whole vascular system is built up of united 



Fig. 159. 

 A, part of central stele; B, the commissural bundle from a young sporophyte of Danaa jcnmani. X150. 



leaf traces and there is no cauline bundle in the strict sense of the word, although 

 we may speak of the bundle, or stele of the stem, as soon as there is a solid central 

 strand formed below the junction of the earlier leaf traces. This primary stele 

 never has the form of a true protostele, however, as the xylems belonging to the 

 separate leaf traces can be recognized and the compound nature of this central 

 bundle is unmistakable. 



