PTERIDOPHYTES 169 
root, while the two inner (dorsally directed) quadrants develop the stem 
and leaf, which pierce through the tissue of the overlying thallus (fig. 
394). Recent investigations, however, indicate that both the outer 
(ventral) quadrants may develop the foot, the two inner (dorsal) quad- 
rants forming a tissue that gives rise 
to leaf, stem, and root. This method 
of development suggests that of the 
embryo of Ophioglossales, with which 
group the Marattiaceae seem to be 
closely allied. 
Among Polypodiaceae the first divi- 
sion of the egg is parallel with the 
long axis of the archegonium (fig. 
395), the shoot cell being directed 
towards the apex (notch) of the pro- 395 
thallium. At the quadrant stage (fig. FIGS. 394,395. Diagram of quad- 
395) the two apicallv directed quad- rant stage of embryo: 394, Marattia, in 
F / which the first wall is transverse to the 
rants give rise to stem and leaf (the long axis of the archeg o n ium, the 
latter being ventral) ; while the two shaded quadrants giving rise to stem 
basally directed quadrants give rise f d leaS ,> 395, a polypod, in which the 
. first wall is parallel with the long axis 
to foot and root (the latter being of the arc he g oniuin, the shaded quad- 
ventral). The Stem and leaf, directed rants (directed towards the notch) giv- 
tOWards the notch, grow under the jn g rise to stem (upper quadrant) and 
. leaf (lower quadrant); in both cases 
prothallium and the leaf turns up the notch is to the right, 
through the notch. In such a case, 
the foot is the most temporary organ, functioning only so long as the 
gametophyte endures, while the primary root does not exist for a long 
time. The relatively permanent structures of the sporophyte are the 
stem, giving rise to secondary roots, and the leaves. 
Apogamy and apospory. The phenomenon of apogamy is so preva- 
lent among Filicineae that it deserves special mention. Apogamy is 
the production of a sporophyte by a gametophyte without the act of 
fertilization. Such a sporophyte may arise either from the unfertilized 
egg, in which case the apogamy is called parthenogenesis; or it may arise 
from the vegetative tissue of the prothallium, in which case it is called 
vegetative apogamy. It is found to be very common among ferns, and 
can be induced with little difficulty. 
The companion phenomenon is apospory, in which a gametophyte 
is produced by a sporophyte without the formation of a spore. These 
