666 CONCLUSION 
undergoes octant-division:} the succession of the divisions is not always 
the same, but as a rule there is first a basal wall (x, B) parallel to the 
wall 1, 1, which divides the embryonic cell into hypobasal and epibasal 
tiers, and this is followed by quadrant and octant walls at right angles 
(Fig. 355 Q, Q; 0, 0), which divide each of those tiers into quarters. The 
result is a body which shows in many cases, by its elongating form, that 
there is a distinct polarity: its form and constitution are illustrated by 
diagrammatic figures (Fig. 355 1. 11), im which the suspensor is cross- 
hatched, the hypobasal tier dotted, and the epibasal tier left clear. Such 
a scheme will serve for all Pteridophyte embryos with suspensor which 
have been fully elucidated. 
Turning to embryos without a suspensor, the segmentation of the whole 
zygote into octants is similar to that seen above in the embryonic cell, 
where a suspensor is present, but with the suspensor completely omitted 
{compare Lguisetum, Fig. 214; Ophioglossaceae (excl. Botr. obliguum), 
Figs. 260, 261, 261; Jsoe¢es, p. 350; and all Filicales). It is represented 
diagrammatically in Fig. 355 ul., where again the hypobasal region is dotted 
and the epibasal left clear. Without attaching undue importance to the 
cell-cleavages themselves (for they resemble those in certain quite distinct 
bodies, such as capitate hairs), they may be held as indications of the 
growth, and, what is more important, of the polarity already defined in 
the body of the embryo. The first indication of the existence of this 
polarity is given by the position of the first segment-wall (1, 1), or B, B 
in cases where a suspensor is absent; and it may be shown that in all 
fully investigated cases the apex of the axis has a definite relation to that 
first wall. It appears at the centre of the epibasal hemisphere, that is, 
in close relation to the intersection of its octant walls: the point is 
marked (#) in the diagrammatic Figures 355 1., IJ., IIL 
It should be clearlygunderstood that however constant the orientation 
of the embryo may be in cases where a suspensor is present, the orienta- 
tion is not constant in the type without a suspensor: in these the apex 
of the axis bears no necessary or constant relation to the axis of 
the archegonium, either for Archegoniate plants at large, or for the 
several phyla of them, or yet for genera or even for individuals. As a 
matter of observation, the orientation of the definitive shoot is initiated 
sometimes with its apex towards the neck of the archegonium (compare 
Fig. 214 of Zguisetum, and Figs. 260-262 of the Ophioglossaceae, with 
the diagrammatic Fig. 356 11.); or obliquely to one side, eg. Lepto- 
sporangiate Ferns (compare Figs. 14, 15 with diagrammatic Fig. 356 i1.); or 
away from it (as in Marattiaceae, compare Fig. 292 with the diagrammatic 
1Compare especially Fig. 190 ot Se/ spinulosa; also, though less clearly, Pfeffer’s 
drawings of S. Martensit, Hanstein’s Abhandl., vol. i. Taf. 2, 3; Treub’s drawings of 
Lye. Phlegmaria (Fig. 185), but more fully in Ann. Jard. Bot. Buit., vol. v. Taf. xxiii., 
xxiv., and Bruchmann’s drawings of Lyc. clavatum and annotinum (Fig. 186); but more 
fully in Bruchmann’s own memoirs quoted above. 
