87 
and Affinities of Trap ell a. 
be that when this little known region is more thoroughly 
worked out, Trapella may turn out to be a fairly common 
plant. 
Development of the flower . — In the youngest buds that I 
have been able to investigate, all the organs were already 
formed. Fig. 1 6 is an antero-posterior section of a bud 
less than i mm. long. In it are seen the functional and 
reduced loculi of the ovary (loc. and red. 1. respectively), and 
the insertion of the upper sessile ovule (ov. 1 ). The lower 
ovule — which originated side by side with the upper — fills 
up the rest of the cavity of the ovary, but is not represented 
in the figure, since its point of insertion cannot be given. 
In Fig. 17 is the section at right angles to the antero-posterior 
plane, showing the insertion of the stamens and the state of 
pollen-development. As yet the pollen-mother-cells (p. m. c .) 
are undivided, and lie enclosed in the tapetal layer {tap.). At 
this stage about equal parts of the ovary are inferior and 
free respectively, and the vascular bundles, drawn darker, show 
some differentiation, though of course they are not lignified 
as the parts have still to undergo great stretching. Gradually 
the lower part of the ovary elongates, leaving the ovules 
high up, attached to the axile placenta quite at the top 
(Fig. 1 5) : then later on, after fertilization, the uppermost 
ovule comes almost to fill this deep ovary. 
Development of ovule and embryo-sac . — Up to a certain point 
the developmental history of both upper and lower ovules is 
identical ; since, however, in all cases it is the upper one only 
which becomes a seed, it will be the history of this one which 
I shall follow, except where otherwise indicated. 
The ovule is essentially anatropous from a very early stage 
(Fig. 2,4). The nucellus is small in comparison with its 
developing integument (ct). In stages a trifle earlier than the 
one figured, the undivided archesporial cell may be seen, 
occupying the upper part of the nucellus, and invested only by 
a single epidermal layer. In Fig. 24 the archesporium has 
divided into two cells : an upper one (e. s. m. e.), which is the 
embryo-sac mother-cell, and a lower one (c), which later will 
