354 LYCOPODIALES 
‘of a root. An alternative view was there propounded that the Lycopod 
embryo is a body prone to parenchymatous swelling, and that the 
“protocorm” is a consequence of secondary specialisation. It remains to 
group the facts of embryogeny in the eligulate Lycopods in accordance 
with that alternative view. 
The simplest type of embryogeny in the genus is that of Z. Seago, 
a species already recognised as primitive in the characters of the sporophyte. 
The embryo accommodates its growth in length to the level of its parent 
prothallus ; excepting for this the embryo is of a constant type, without 
any complications of parenchymatous swelling. I regard this as a primitive 
condition for the genus, and the main features are these: a suspensor 
and foot of moderate size, passing directly into the primitive shoot, which 
escapes early from the prothallus, and expands its first leaves as green 
assimilating leaves. The apex of the axis, which provides a definite leaf- 
succession, is established early at the centre of the upper tier; the first 
root is formed early and exogenously, and it is followed soon by others of 
endogenous origin. Thus the young plant is simply and directly set up 
as an independent unit (Figs. 183, 184). The type most nearly corre- 
sponding to ZL. Se/ago is that of Z. Phlegmaria. Notwithstanding the pro- 
nounced saprophytism of the prothallus, the embryogeny is practically 
identical in all essentials with that of Z. Se/ago, though more exactly 
worked out (Fig. 185). But it is different with the clavatum-annotinum-type. 
Here the primary embryogeny is the same as in Z. Phlegmaria, but the 
deeply underground position of the saprophytic prothallus necessitates longer 
and more efficient nursing of the embryo before it can establish its 
physiological independence. The. absorptive surface and storage capacity 
of the embryo are accordingly enlarged by parenchymatous swelling of 
the foot. The directness of the adaptation is here indicated by the fact 
that the enlargement is on whatever side is nearest to the greatest source 
of supply. The late differentiation of the several parts, and the tardy 
emergence of the embryo from the prothallus, are all in accord with the 
necessarily longer nursing period: while the colourless scale-character of 
the earliest leaves is also a natural and secondary consequence of the 
subterranean embryogeny. It is not difficult to see in the clavatum-type 
an embryogeny essentially like that of Seago, but secondarily modified in 
relation to the subterranean habit of the prothallus. This accords well 
with the fact that the species included are more highly specialised than 
Z. Selago as regards the characters of the sporophyte (Fig. 186). 
The cernuum-inundatum-type on general characters of its prothallus and 
sporophyte takes a middle, position. The embryogeny opens as in other 
Lycopods: but the foot-tier, which is enlarged in the clavatum-type, here 
remains small. The ortgin of the cotyledon is as in Z. Se/ago, but the 
swelling in the upper tier, which begins early on the side directed down- 
wards, profoundly disturbs the subsequent arrangements, so that detailed 
comparisons become difficult, and, as a consequence, the origin of the axis 
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