70 



THE OPHIOGLOSSALES 



from the apical meristem of the shoot. The latter, as in the other Ophioglossaceae, 

 shows a large single initial cell, which in section closely resembles that of Ophto- 

 glossum moluccanum, having a broadly truncate base and being narrower above 

 (fig. 46, D). The apical meristem is of very limited extent and segmentation of the 

 apical cell is probably very slow. The second root, which in the case under con- 

 sideration arose near the base of the third leaf, is here very conspicuous and its stele 

 joins that of the third leaf near the base of the internode. The young leaf and root, 

 with the inconspicuous stem between them, have very much the appearance of a 

 bud at the base of the second leaf. The apex of the very young leaf grows from the 

 conspicuous single apical cell (fig. 46, Z)). This appears triangular in longitudinal 

 section and shows regular segmentation. The stele of the young leaf can be traced 

 up to the inner cells, cut oflF from the lateral segments of the apical cell. 



The apical cell of the stem is quite large and, as we have seen, is truncate below, 

 as it is in Ophioglossum. Seen in its transverse section it is triangular, so that its 

 form is really that of a three-sided prism. Both lateral and basal segments are cut 

 off from it, but only the youngest segments can be clearly distinguished. Below the 

 apical cell there is only a very small amount of tissue between the apex of the shoot 

 and the point of the junction of the two leaf traces and the stele of the second root. 

 This junction is marked by the presence of very irregular reticulate tracheids (fig. 

 46, D, tr). The tissues on the upper side of the root stele extend to within a few cells 



of the stem apex and may possibly 

 represent a portion of the internodal 

 stele that is not connected with the 

 leaf trace, but a study of later stages 

 does not support this view, and it 

 is almost certain that this youngest 

 tracheary tissue is the beginning of 

 the next leaf trace. 



From the very first, as Lang 

 pointed out, the shoot is perfectly 

 dorsiventral, although at first it grows 

 vertically upward. The leaves are all 

 borne upon the dorsal side, while the 

 roots invariably arise upon the ven- 

 tral side. 



The apex of the young root, 

 which in this case is on the point of 

 emerging, is occupied by a conspicu- 

 ous triangular apical cell, the segmen- 

 tation of which closely resembles that 

 of the root o( Botrychium. At first the root cap is mainly derived directly from the 

 outer segments of the apical cell. These segments undergo periclinal as well as 

 anticlinal divisions and the inner layers of the root cap (which at this stage is rela- 

 tively thick) show a fairly regular stratification. The outer cells of the root cap are 

 a good deal elongated, so that the free end of the root is decidedly pointed. At this 

 time, except for the irregular conjunctive tracheids at the base, no permanent tissue 

 can be seen in the stele of the young root. 



In the cross-sections of a young sporophyte of about the same age the third leaf 

 was rather further developed and the young fourth leaf could be seen, but the second 

 root was not so far advanced, or it may be that the root at the base of the third leaf 

 was the third root and not the second. The single apical cell, which was so prominent 



Fig. 47. — -Transverse section of young sporophyte of Hdminthos- 

 r^ac/i^yj, above terminal bud. /^,/*, lacunae; /^, second leaf. X65. 



B. Section passing through base of bud. f, young root. X 100. 



C. Stem apex. X2C». 



