178 



cylinder of the stem. Hy this time also the central vascnlar 

 strand of the leaf is clearly evident, and the apical cell of the 

 leaf is readily made out. It is, however, not until a much 

 later stage that the tracheary tissue is formed. 



The root of the young bud does not emerge until the leaf 

 is nearly complete. From this time on the further growth is 

 due to the activity of the stem apex, from which the new 

 leaves and roots are presumably developed in the same way 

 as in the other species that have been studied. How long it 

 is before fertile leaves are developed was not ascertained, but 

 in the rapidly growing species of a tropical climate it is likely 

 that this takes place before long. The occurrence of very small 

 fertile individuals (Fig. 154) points to this. 



ANATOMY OF THE YOUNG SPOROPHYTE. 



In (). pendulum the young primary root soon breaks through 

 the prothallium and rapidly elongates, but owing to its britt- 

 leness, it is easily broken off, and it is impossible to state here 

 just how far it develops before the bud is formed upon it. The 

 development of the second root varies much. The first root 

 sometimes reaches a length of three or four centimeters before 

 the second root can be seen at all. The growth of roots is in 

 all respects similar to that of the later ones. There is a large 

 tetrahedral apical cell whose divisions are quite regular, and 

 there is soon visible the axial vascular bundle which extends 

 for some distance into the foot, where it ends blindly. The 

 vascular bundle of the second root joins the first at the junction 

 of bundle of the latter with that of the foot (Fig. 127). 



The first tracheary tissue appears at the point of junction — 

 short, somewhat irregular pointed tracheids with reticulate 

 thickenings. Fi'om this point the development of the tracheary 

 tissue proceeds toward the apex of the roots. As in the later 

 roots, the bundle is diarch, as is plainly seen from cross sections 

 (Fig. 144). The endodermis is very clearly defined, and the 

 characteristic radial markings are extraordinarily clear, especially 

 in sections treated with a double stain of safranine and gentian 



