30 Humphrey . — The Development of the 
of the seed to such an extent that only a thin layer of nucellar 
tissue is left within the seed-coat, and this soon loses its cellular 
structure by compression {psp . , Fig. 54). A massive endo- 
sperm is formed in the cavity, but never wholly fills it. In 
the centre of the cavity is formed the almost cylindrical 
embryo (e. s., Fig. 55), and the space between it and the 
remnant of perisperm is occupied by a permanent endosperm 
containing starch except in its outer cell-layer, which forms 
an aleurone-layer. In the ripe seed the perisperm forms a 
mere film against the testa {psp., Fig. 56). In this species, 
then, we have a Scitamineous plant without functional peri- 
sperm. 
I have examined neither of the species of Ravenala. 
The remaining genus, Heliconia , has furnished the most 
complete material studied from this family. The work has 
been done chiefly on //. psittacorum , L. hi., though H. Bihai , 
L., shows the same features so far as comparison has been 
possible. 
Except for a few figures given by Richard (’ 31 ) of his 
H. cannoidea, which well show the general appearance of 
fruit and seed, and some similar, though not better, figures 
by others, I have found no references in the literature to the 
seeds of this genus. The ovary becomes a three-seeded 
septicidal capsule. 
In the earliest stage observed, the ovule shows both integu- 
ments in process of formation and an embryo-sac mother-cell 
which is separated from the nucellar epidermis by a tapetal row 
(Fig. 57, PI. IV). A little later, this mother-cell has divided 
into three cells (Fig. 58), and still later into four (Fig. 59). 
Four is the usual number of cells in the row thus formed, but 
I have seen five in at least one case (Fig. 60). Soon the 
lower cell of the series begins to enlarge at the expense of 
the others (Fig. 61), and finally it becomes the embryo-sac by 
the absorption of all between it and the nucellar epidermis, 
which meanwhile and later thickens into a micropylar pad 
(m.p., Figs. 63, 66). During this time the ovarian cavity has 
grown with the ovule, so that the latter has filled but a small 
