' M l
34 ON THE FERTILIZATIO>-
p o i n t e d processes passing off f rom it in rarious directions (Plate V, fig. 11), and that in the
course of evolution it becomes separated into a central, prominent dilation, and a seiies of
horn-like cells radiating from it. Be this as it may, at this stage there is a prominent
c e n t r a l cell pressing down upon the outer surface of the embryo-sac, and two or more
elongated peripheral ones arising from it laterally and clasping the adjacent surfaces
of the sac (Plate V, figs. 14, lo). At this period the apex of the embryo-sac is still
r e a d i l y separable from tho cells, the site of contact with the central one, however,
b e i n g sometimes recognisable after separation has taken place, due to its staining
d i f f e r e n t l y from the rest of the sac-wall (Plate V, fig. 13). ' The ccntral cell continues
t o increase more and more in prominence, pressing down, invaginating, and apparently
u l t i m a t e l y penetrating through the apex of the embryo-sac, and, at the same time,
t h e peripheral cells shoot out into long horn-like processes with dilated bases adherent to
t h e sides of the central one, and frequently sliowing soeondary dilations farther out, which,
l i k e the basal ones, are nucleate (Plate V, figs, 12, 14, 15). From their position and relations
to neighbouring stnictures, these lateral processes appear to be specially adapted to fix the
c e n t r a l cell as it presses down on the apex of the embryo-sac. Subsequently, as the result
of a process of free-cell formation, or rather, perhaps, of rejuvescence followed by celldivision
on the part of the contents of the central cell, a series of three cells arises within it
a r r a n g e d in linear series (Plate V, fig. 12). The two first of these appear to play the part
of a suspensor, the basal one appearing to be adherent above to the membrane of the mothercell,
and therefore through it to the under surface of the apical cap of the nucellar
parenchyma. The distal or inferior cell swells up, becoming, first, more or less hemispherical
a n d then broadly clavate, and the dense protoplasmic contents give origin by free cell
division to an aggregate of nucleate protoplasts constituting the pro-embryo (Plate V,
figs. 12, 14, 15). At this stago the central cell and its contents measure about 0-033 x 0-016
mm. Subsequently, as increased growth in the secondary cells goes on, they come to press
upon the interior of the walls of the parent one, and its outlines become undistinguishable.
T h e embryo-sac remains apparently structui-ally unaltered for a short time after the
access of insects to the receptacle, merely increasing in capacity, due to accumulation of
fluid witiiin it. At a period when the embryogenic cell already has begun to enlarge,
a n d its central portion to press down on and adhere to the apes of the sac, the latter
continues, in some cases at all erents, to retain its original, single, large nucleus (Plate V,
fig. 13). A little later, however, this disajipears, and is replaced by a large number of
much smaller secondary ones, which are scattered over the inner surface of the wall of
t h e sac, and at the same time an increase in tho substance of the network of cytoplasm
seems to occm- (Plate V, figs. 9, 10). So long as the embryogenic cell merely depresses
t h e apex of the sac, the latter is readily separable under the influence of reagents from
t h e apical cap of the nucellar parenchyma, but after adhesion or actual perforation of
t h e apex has occurred, this is no longer the case, and the sac adheres so firmly to the
cap that on several occasions I have been able to detach them from the rest of the
ovule en masse by tearing off the micropylar extremity, the lower portion of the sac
b e i n g drawn out of the inferior half of the ovule in the process of removing the two
portions from one another. Time has not yet sufficed for an examination of the details
of the evolution of the embryo after this stage has been reached, and I have therefore
t o proceed next to a description of certain of the characters presented by the mature
flowers and their seeds.
OF PIOUS EOSBUEGflir.
C.—Characters of femaU jloiocrs in ma/ure receptacles which have been entered by insects.
Tho following figures show the measurements of two mature flowers from the si
r e c e p t a c l e :—
1. Flower provided with a well-developed pedicel—
Total height from base of pedioel to apex of ovary 5'6I mm.
Height from base of pedicel to origin of perianth 2 85 mm.
Total height of ovary .q j
Height from the upper edge of stylar insertion to »pes of ovary , . . 0 -6 mm,
Breadth of ovary at level of upper edge of stykriusertion . . . . 0-88 mm.
Length of style and stigma ^^
Breadth of stigma CU mm!
Height of base of ovary above tips of perianth o-2 mm
2, Flower absolutely sessile-
Total height fro-n base, i.e., origin of perianth to summit of ovary . . 2-02 mm.
Height from base to level of bifuroation of tbe fibro-vnscular buadle, . 0-79 mm.
Height from bifurcation of fibro-vascular bundle to base of ovary proper 0'2 mm.
Total height of ovary Qg
» Height from the level of upper edge of stylar iosertion to summit of
mm.
Breadth of ovary at level of upper edge of stylar insertioa . . . . 1-08 mm.
T h e following are the dimensions of an exceptionally tall flower :—
Total height from base of pedioel to summit of cutiaular slieath of
6-46 mm
Height from base of pedicel to origin of perianth
Height from origin of perianth to level of lifm'cation of iibro-vascular
bundle
Heiglit from bifurcation of flbro-vascular bundle to base of aoheno . 0-5i mm'
Height of aohene ^ gg
Height from summit of acbene to cuticular sheath of summit of ovary! 0-28 mm'
Height frum level of upper edge of atylar insertion to summit of
o^-wy
Ereadth of ovary, including gelatinous sheath, at the level of upper
0--6 B
edge of stylar insertion 1'22 mm
Breadth, esclading gelatinous sheath J QQ
T h e total hsiglit of the flowers now Taries very greatly on aoconnt of the varying
amount ot elongation of the axis, both below the origin of the perianth and between this
point and the base of the ovar j proper, whieh has taken plaee i n different instances (Hat e
I I I , % . 4). Iho peduncle is softened and semi-transparent, so that the fibro-vascular handle
can be seen shimng through its snbsfanee. The lobes of the perianth retain their oririnal
s r » and are wel preserved, not showing any signs of softening, but being dried up and of
I d tl' b r • '« " - a
and the base of the ovary is nmeh softened, and the tissue to a great extent converted into
« t r a n s p a r e n t platrnous snhstanee in which tire bifurcation of the vascular bundle bene" h
tire ovary can be rcad.Iy seen. The cuticular stratum of the entire ovary is widely s e p a ^ d