EMBRYOLOGY 349 
its greatest development is not always in the plane of the median wall, 
but on that side from which the greatest quantity of nutriment flows from 
the prothallus, and this brings about a torsion which the suspensor does 
not prevent. In fact, the “foot” is here an:opportunist growth, inconstant 
in position itself, and distorting in a variable manner the rest of the embryo. 
Soon after the origin of the first two leaves follows the origin of the first 
B A 
Fic. 186. 
Az=young embryo ot Lycopodium annotinum. .-I.=the basal wall; I1.-II].=the 
transverse wall; IV.-1V.=the wall separating the foot-tier from the stem-tier. S=an 
older embryo of Z. clavatunz, showing more advanced development of the two tiers, and 
especially of the foot-tier. © =an older embryo detached, with cotyledons (£71), a further 
leaf (BZ2), and the first root (4), and foot (7). MD=young underground, colourless 
seedling ; #=foot ; H’=root; M’,=origin of a second root ; &/=leaf-scales, of which the 
first pair are the cotyledons. A and BX150. Cx52. Dxx10. (After Bruchmann.) 
root, in a position variable relatively to them (Fig. 186c). The embryo 
then bursts the tissue of the prothallus, as a consequence of active inter- 
calary growth of the hypocotyl, which emerges upwards, while the root 
enters the soil downwards (Fig. 186D). The axis while growing through 
the soil is pale, and bears only colourless scale-leaves, but on emerging 
ultimately at the surface these pass into green leaves of the ordinary foliage 
type (Fig. 179 A). The embryology thus described is more complex than 
that of the Se/ago type: its details are plainly in accordance with the 
saprophytic specialisation of the prothallus, and with its position deeply 
