668 CONCLUSION 
This general principle may be illustrated by comparison of certain of the 
figures quoted in Part II. Thus in Fig. 185 4,8 (p. 348) of Lycopodium 
Phiegmaria the apical point T coincides very nearly with the intersection of 
octants, though it appears unsymmetrical owing to unequal growth caused by 
the precccity of the cotyledon (c), but it is righted by the appearance later of 
the second leaf (Figs. 185 c, D). It cannot be doubted that the case of Z. 
Selago is very similar, though the 
detailed study of cleavages is not 
yet to hand (Fig. 183, p. 346). 
Fig. 186 (p. 349) of ZL. annotinum 
shows the coincidence of the 
apex (Ss) with the cleavage-wall 
(11) very plainly indeed. As 
the cleavages have not yet been 
traced in the more aberrant 
L. cernuum, it is impossible to 
say more than that the ob- 
served facts do not preclude a 
similar origin of the axis, which 
comparison with hyloglossum 
makes probable (p. 353). In ' 
Selaginella spinulosa (Fig. 190, 
Pp. 357) a comparison of the 
stages A, C, D clearly shows 
that the small-celled tissue of 
the apex of the axis includes 
the intersecting octant walls. A 
similar origin of the axis to that 
in Lycopodium and Selaginella 
spinulosa may be traced for 
Ssoetes, notwithstanding the ab- 
a ‘ ' sence of a suspensor and the 
Diagrams to show in view from above and in section how 
growth with a single three-sided initial cell may be estab- small size and late definition of 
lished in an epibasal hemisphere divided into octants. The 
quadrant wall, Q, Q, and the octant wall, ¢, 0, are the first the apex (Fig. I9I, pp. 359- 
of the series of cleavages, continued by the walls z, z, 22, 77, a 
etc. The result is that the initial cell (x) is formed at the 360). The case of S. Martensti 
nearest possible point to the centre, consistent with the " : id i 
sequence of its segmentation. is interesting for comparison, 
since there is a single initial 
cell, a condition which is probably derivative as compared with that of S. 
spinulosa, with its small-celled meristem. Pfeffer’s drawings! demonstrate 
how this originates with the octant wall forming one of its lateral faces; 
in fact, at the nearest point to a central position compatible with its 
existence as a single initial cell. The embryo of Agudsetum shows this 
even more plainly: if a single initial cell is to be carved out of an 
epibasal hemisphere of four octants so as to be as near to the centre of 
Fic. 357. 
1 Hanstein’s Adhandl., i., Taf. iii. iv. 
