206 Tue Lire HISTORY OF 
of the leaf. The larger portion of the two primary bundles unite 
to form the central bundle; these three bundles run parallel with 
the long axis of the leaf and are united with each other at intervals 
by small strands taking an oblique apical course from the central 
one to each lateral one. 
The sporophyll has two deep dorsal grooves, running parallel 
with the lateral bundles and just over them ; in these grooves occur 
' the stomata and glands, and in them are borne the sporangia and 
paraphyses. All the leaves bear scales which show a higher order 
of development as the leaves approach the type of the sporophyll. 
The sporangia are long-stalked and spherical with an annulus 
of about fourteen cells, four lip cells and four connectives. The 
spores are reniform with a smooth outer coat. The smaller cells 
on the pedicel at the base of the sporangium become very much 
inflated and when the sporangium opens they tilt it back, thus 
aiding in the escape of the spores. The paraphyses are long- 
stalked, branched and multicellular; the terminal cells being 
longer, curved, and enlarged at the apex. 
Explanation of Piates 
The figures were drawn with a magnification twice that indicated and the resulting 
figures were reduced one half. 
PLATE 23 
FiG. 1. Under side of a prothallium, showing its irregular branching : a, rhizoids ; 
4, ee 2T. 
. 2. A young prothallium showing sterigmata along margin. X 7. 
Fic. 3. Prothallium showing manner of branching at apex. ۰ 
F 
IG. 4. An older piece with the archegonia just forming. 4, rhizoids ; 4, arche- 
gonia ; c, ¿ei d, young sporophyte. X 9. 
Fic. 5. M 
ore 5. Margin of prothallium at apex, showing branching and 4, sterigmata. 
Figs. 6, 7. oe prothallia starting from margin of old ones. >< 120. 
Fic. 8. A you g prothallium, a, 
single oe of an old, edel x32 
Fic. 
with three growing points starting from a 
. F ; i 
9. Four marginal cells of the prothallium, each one giving rise to a rhizoid. 
. 10. Same as Fig. 9. X 87. 
I. A rhizoid formed from an initial cell. X 87. 
. 12. A rhizoid formed from two cells. % 120, 
> 13. Rhizoid with inflated. cell. 87, 
oo 
mar 
۳ Oo n 
