care being taken that no water is poured over them for a
day or two beforehand.

The first divisions of the fertilized egg cell resemble those in the
moss embryo, except that the first wall is parallel with the
archegonium axis, instead of at right angles to it. Very soon,
however, the embryo becomes very different, four growing points
being established instead of the single one found in the moss
embryo. The two growing points on the side of the embryo nearest the
archegonium neck grow faster than the others, one of these
outstripping the other, and soon becoming recognizable as the first
leaf of the embryo (Fig. 67, _A_, _L_). The other (_r_) is peculiar,
in having its growing point covered by several layers of cells, cut
off from its outer face, a peculiarity which we shall find is
characteristic of the roots of all the higher plants, and, indeed,
this is the first root of the young fern. Of the other two growing
points, the one next the leaf grows slowly, forming a blunt cone
(_st._), and is the apex of the stem. The other (_f_) has no
definite form, and serves merely as an organ of absorption, by means
of which nourishment is supplied to the embryo from the prothallium;
it is known as the foot.

[Illustration: FIG. 67.--_A_, embryo of the ostrich fern just before
breaking through the prothallium, x 50. _st._ apex of stem. _l_, first
leaf. _r_, first root. _ar._ neck of the archegonium. _B_, young
plant, still attached to the prothallium (_pr._). _C_, underground
stem of the maiden-hair fern (_Adiantum_), with one young leaf, and
the base of an older one, x 1. _D_, three cross-sections of a leaf
stalk: i, nearest the base; iii, nearest the blade of the leaf,
showing the division of the fibro-vascular bundle, x 5. _E_, part of
the blade of the leaf, x 1/2. _F_, a single spore-bearing leaflet,
showing the edge folded over to cover the sporangia, x 1. _G_, part of
the fibro-vascular bundle of the leaf stalk (cross-section), x 50.
_x_, woody part of the bundle. _y_, bast. _sh._ bundle sheath. _H_, a
small portion of the same bundle, x 150. _I_, stony tissue from the
underground stem, x 150. _J_, sieve tube from the underground stem,
x 300.]

Up to this point, all the cells of the embryo are much alike, and
the embryo, like that of the bryophytes, is completely surrounded by
the enlarged base of the archegonium (compare Fig. 67, _A_, with
Fig. 55); but before the embryo br