THE OLDER SPOROPHYTE 



171 



formed of rows of large cells which become more or less fused together and their 

 contents, composed of a dense granular mucilage, stain very strongly, either with 

 safranine or with Bismarck brown, which were the principal stains used in preparing 

 the sections. Numerous tannin cells are also present, scattered irregularly through 

 the cortical tissue and also in the vascular bundles. 



Figure 155, B, is a median section through the base of one of the later roots, 

 showing its connection with the corresponding bundle in the stem. The elongated 

 cells (j-c) are the cortical sclerenchyma cells already referred to. These are shown 

 on a larger scale in C and D, where the conspicuous pitted walls can be seen. 

 The shaded cells in the figure are tannin cells. 



Figure 156 shows cross-sections taken at different heights from a sporophyte of 

 D.jenmani, a plant of about the same age as that which was shown in the preceding 

 series of longitudinal sections. Sections made near the apical region. A, B, and C, 



Fig. 155. 



A. Another section of specimen shown in fig. 154. 



B. Base of a root showing sclerenchyma, 5c, in cortex. X40. 



C. Sclerenchyma cells, showing pitted walls. X320. 



D. Surface view, showing pits. 



show two pretty well advanced leaves and the first trace of a third, the apex of which 

 is indicated in C and E. UnHke the earher leaves with their single leaf trace, these 

 later leaves, as we have seen, have the petiole traversed by two vascular bundles 

 whose sections are plainly visible. These, as we have remarked from a study of the 

 longitudinal sections, fuse into one near the base of the leaf (A), and two small 

 bundles are also present on either side, belonging to the stipules. As the sections 

 are followed downward, the main bundle is found to divide into the double leaf trace 

 entering the stem, and the two small stipule bundles become united with these, so 

 that within the stem, at about the level of the stem apex, two distinct bundles are 

 seen, corresponding to each leaf. The leaves are now arranged in two series, 

 indicating that the dorsiventral character of the stem in this species is established 

 and the youngest leaf lies almost opposite the next youngest one, whose leaf traces 

 can be seen. E shows the stem apex with the apical cell, x, and the youngest leaf 

 rudiment, /. 



