164 THE MARATTIALES 



to demonstrate an external endodermis in the stem bundles o(Jngwpterts,Marattia, 

 and Kaulfussia, and presumably similar treatment would show its presence in the 

 young s'em of -Dan^fl. 



It is evident that we can not speak of the young sporophyte in Daneea jamat- 

 censis as possessing in its early stage a " protostele," or "haplostele," to use Brebner's 

 terminology, unless we choose to call the single leaf trace of the cotyledon a protostele. 

 Just so soon as the two first leaf traces unite, the axial vascular bundle of the young 

 sporophyte has two quite independent xylems. 



Figure 147 is a longitudinal section of a sporophyte of D. elliptica, slightly 

 older than that of D. jamaicensis shown in fig. 138. The second leaf (/') had already 

 begun to develop the lamina, whose apex was forked so that there were two veins 

 present. A longitudinal section of one of the two leaf lobes is shown in D. The 

 stem apex closely resembles that of D. jamaicensis, the apical cell having much the 

 same form and size. The stem apex does not lie in the same plane as the leaf traces 



B 



Fig. 147. — Danaa elliptica. 



A. Nearly median section of a young sporophyte, showing 



origin of second root, r^ . X35. 



B. Central region. X150. 



C. Median section of second leaf. 



D. Apex of second leaf. X150. 



E. Stem apex, X150. 



^35- 



and hence does not show in the figure, which is a section passing directly through 

 the leaf traces. This plant showed very clearly the very earliest stage of the second 

 root (fig. 147, A, r). The apical cell of the young root is cut out from one of the cells 

 of the parenchyma below the stem apex, lying almost exactly half-way between the 

 two primary leaf traces. Only a single segment had been cut off from the apical 

 cell in this case and both the apical cell and this primary segment were easily dis- 

 tinguished from the surrounding tissue by their denser contents. There is nothing 

 to indicate that the cell which had assumed the function of the root initial was in 

 any way essentially different from the neighboring cells. If it is an endodermal cell 

 there is no way of recognizing this, as the endodermis could not be recognized in 

 this part of the sporophyte. Figure 147, B, shows an enlarged view of this young 

 root initial, lying above the junction of the two primary leaf traces. Conspicuous 

 reticulate tracheids with pointed ends are present in the trace from the cotyledon, 

 but as yet no permanent tissue has been developed in the bundle from the second leaf. 



