Seed in the Scitamineae . 
25 
Binn. ( — A ntomum), Elettaria sp., and A Ipinia mutica , Roxb., 
the characteristic inner layer of the outer integument continues 
over the apex of the embryonal cavity, thus forming both 
faces of the collar and the germinal lid (Fig. 37). At the 
point of junction of lid and collar there is a break in the 
continuity of the layer, which makes it easy for the embryo 
to push out the lid in germinating. It will be noticed that, 
in the formation of collar and lid, all these genera differ from 
Costus. The form of aril above described has been met with 
only in Costus. On ripe seeds of Amomum , Elettaria , and 
Alpinia one finds no marked micropylar excrescence, but 
a soft, loose, veil-like covering over the whole seed (ar. Figs. 
37, 39), which is attached to the underlying tissues only at 
that end. An examination of the ovules shows the origin of 
this enveloping structure. From the micropylar end of the 
outer integument arises a downward outgrowth, and from the 
inside of the funiculus just above the micropyle arises another 
outgrowth which extends across the micropyle and then 
downward over the first-named one. From the back side 
of the funiculus arise two corresponding outgrowths that 
extend downward and form a double covering for that side 
of the ovule (ar., Fig. 34). That the adult aril is really 
double may be seen on careful examination near the point 
of origin (ar., Fig. 39). The ovules of Alpinia alata, A. Dietr., 
and Globba bulbifera , Roxb., show similar outgrowths, and 
probably their seeds have similar enveloping arils. The use 
of this form of aril to the seed is not easy to suggest. The 
aril of Costus much resembles those of the Marantaceae, and 
may well play a part in the rupture of the capsule and the 
escape of the seeds. And it is possible that this soft, yielding 
envelope outside of the firm testa may, when fresh, have the 
power of swelling and causing the bursting of the fruit. 
The seeds of Amomum and Elettaria show no sign of the 
dense chalazal mass found in those of Costus. But the ovules 
of Globba show the beginning of a similar development; while 
in the seeds of Alpinia mutica it is carried much farther than 
in Costus . On the nearly ripe seed of this species there may 
