93 



calypti-a. It is at first a somewhat flattened cone with a single 

 two-sided apical cell. As in most ferns the more rapid growth 

 of the outer side causes it to curve inward and the differen- 

 tiation of the petiole and lamina is soon evident. The latter, 

 while still quite small, devides into two lobes of unequal size 

 of which one becomes the basal lobe of the cotyledon ; the 

 other forms the second lobe, but also includes the apex which 

 continues to grow. It is not quite clear whether the formation 

 of the two lobes of the cot^dedon is to be considered as the 

 result of a monopodia! branching, or whether there is an unequal 

 dichotomy (PI. X, Figs. 55 and 58). 



Figs. 120 and 121 (PI. XIV) show longitudinal sections of a 

 young sporophyte shortly after it has emerged from the calyptra. 

 The foot is conspicuous, and between it and the base of the 

 cotyledon is a region of some extent which may be considered 

 to belong to the stem. The stem-apex is inclined and projects 

 but little. A single initial cell can be plainly seen. This is 

 usually, at least, of tetrahedral form, but narrow as seen in 

 longitudinal section. In cross section it appears as a nearly 

 equilateral triangle (PI. XIV, Figs. 126, 128). In some cases the 

 base of the apical cell appears to be truncate, but this may have 

 been due to the section having been cut somewhat obliquely. 

 The segments of the apical cell divide first into an inner cell 

 which contributes to the central cylinder of the stem, and an 

 outer cell from which arises the cortex and epidermis. The 

 arrangement of the tissues of the young leaf is very similar 

 to that of the stem, and the central strand of procambium- 

 cells joins the stem-bundle a short distance below the stem- 

 apex. Similar axial bundles are developed in the primary root 

 and a short one in the foot, all four bundles uniting in the 

 young sporophyte (PI. XIV, Fig. 121). The development of the 

 permanent tissues of the bundles begins near the point of junction 

 of the young bundles, and proceeds toward the apices of the 

 respective organs. All of the first formed tracheids are reticu- 

 lately marked. 



The root does not differ from that of other ferns. The tetra- 



