ENDOSPERM OF UTRICULARIA 7 
That portion of the placenta immediately beneath the ovule 
begins modification before the megaspores are formed. An ovoid 
mass of tissue, involving a thousand or more cells, begins to 
stain more deeply and soon becomes sharply delimited from the 
surrounding tissue, the cells differing both in size and shape as 
well as staining reaction (Fig. 11). 
This mass of tissue may include several thousand eells des- 
tined to receive the micropylar haustorium and is thus clearly 
marked out long before fertilization has taken place. Its later 
behavior will be taken up with discussions of the female game- 
tophyte and the endosperm. The cells adjacent to this nutri- 
tive tissue specialize along very different lines, especially do 
those on the funicular side become large and greatly elongated 
(Fig. 16). 
FEMALE GAMETOPHYTE 
The female gametophyte developes in the usual manner from 
the innermost of four megaspores that lie in linear series (Fig. 
3). These are bounded externally by a thin nucellus consisting 
of a single layer of cells. Before the first division of the domin- 
ant megaspore the nucellus begins to break down at the tip (Fig. 
4) and soon disappears entirely, leaving the naked female game- 
tophyte protruding from the ovule (Fig. 5). 
Meanwhile the single massive integument has arched over and 
pushed down parallel with the funiculus, and by the time the 
embryo-sac has reached the two-nucleate stage the integument 
touches the placenta at the base of the ovule (Fig. 5). But the 
female gametophyte, as noted above, has escaped confining struc- 
tures at this end; it quickly makes contact with the placenta and 
begins digesting its way into this tissue (Fig. 6). 
It follows, therefore, that no micropyle is really developed 
since the gametophyte, after the megaspore stage, is never com- 
pletely enclosed. A pseudo-micropyle is formed with contact 
between integument and placenta, but sections at right angles 
show that the female gametophyte has lobes on either side 
reaching out into the ovarian chamber (Fig. 9). These protru- 
sions of the embryo-sac are later encountered by the pollen tubes 
moving downward over the surface of the placenta among the 
ovules. 
