672 CONCLUSION 
origin of the first root is again fully illustrated within the Lycopods: 
in Selaginella (Fig. 190) the first root originates laterally from the hypo- 
basal tier, and near to the suspensor: in Lycopodium (Figs. 183, 185, 
186, 188) and in Jsoetes (Fig. 191) it springs from the epibasal tier, and 
is thus necessarily in a lateral position upon the whole embryo. Its 
orientation relatively to the cotyledon also varies: in Jsvetes it is opposite 
to the cotyledon (Fig. 191), in Lycopodium and .Selaginella it is frequently 
on the same side of the axis as the cotyledon, but this is not constant 
in S. sfinulosa: in Ferns it is on the same side as the cotyledon (Fig. 
-15). It thus appears that the root is not definite in level or in orienta- 
tion relatively to the other parts; while in point of time, its extreme 
delay in JZ. cernuum and its absence in Salvzmia are cases too well 
known to require remark. It is notable that though the root in Seed- 
Plants directly faces the suspensor, this is not the case in any: Pteri- 
dophyte: in them it is always a lateral appendage, however nearly it may 
sometimes approach the centre of the hypobasal hemisphere. Accordingly 
it cannot be held to be itself the continuation of the primitive axis. 
Though the root may appear late in the embryology of certain Lycopods, 
the converse is seen in the Ophioglossales ; in them the precocity of the root 
upsets the balance of parts usual in other embryos. This is seen in moderate 
degree in such types as Botrychium virginianum (Fig. 261) or B. obliquum 
(Fig. 264), in which, though the embryo differentiates slowly, the root soon 
takes a prominent place; but in Botrychium Lunaria (Fig. 263) and 
Ophioglossum vulgatum (Fig. 260, 260 és) it is clear that the root, rushing 
forward in its development, outstrips the other parts, and becomes the 
prominent feature of the embryo. The extreme is, however, found in 
Oph. pendulum, and so prominent is the root here that Campbell has 
described the embryo as consisting of ‘roots only.”1_ This may probably 
be held as the consequence of precocity of the root carried to a greater 
degree than in other species: and the precocity finds a ready biological 
meaning in its mycorhizic function. It may be held that the embryo 
hurries it forward as an accessory aid to nutrition, and the parts of the 
shoot are correlatively delayed till sufficient store is at hand to justify 
their development above ground. 
Though the balance of parts in the embryo may be thus disturbed by 
the precocity of certain parts, still more profound disturbances appear 
associated with parenchymatous swellings of the nature of haustoria or of 
storage tubers, and these are usually accompanied by considerable curvature, 
and distortion of the axis. Such swellings are of two sorts: intra-prothallial 
haustoria, to which the name “foot” has commonly been applied, and 
extra-prothallial tubers, known under the name of “protocorm.” In simple 
types of embryo with suspensor the hypobasal tier of the embryo may 
remain small, though. functionating as an haustorium (Z. Selago, Fig. 183, 
and L. Phlegmaria, Fig. 185): but in others it may enlarge in the direction 
1 Ann. Jard. Buit.,-vol. xxi., p. 189. See remarks on p. 469 above. 
