Seed in the Scitaniineae . 1 1 
is nearly reached, their radial walls begin to thicken. This 
thickening is greatest at first at their outer ends (Fig. 18 a), 
but finally the whole cell-lumen becomes obliterated except 
a small cavity at the base filled with granular remains of the 
cell-contents, and a smaller space at the outer end. A faint 
line connecting these remnants of the cell-cavity marks the 
place where the thickening walls have met (Fig. 19 a). The 
appearance of a well-defined ‘light line’ at about one-third of 
the length of these cells from their outer ends (/. /., Fig. 19 a) 
marks them as the true 4 Malpighian cells,’ so characteristic 
of the coats of many seeds. Overhage (’ 87 ) states that the 
walls in the region of this line are lignified, as Mattirolo has 
shown to be true for many other seeds. When these walls begin 
to thicken, those of the four or five cell-layers just below 
commence the same process (set., Fig. 18). This leads to the 
development of the second histological element of the testa, 
the sclerotic layer (set., Fig. 19). The remaining tissue of the 
outer coat remains thin-walled (nut., Fig. 18), and during the 
ripening of the seed is gradually compressed, until there 
remains only a thin band in which the original cellular 
structure is hardly recognizable (nut., Fig. 19). It seems 
probable that these cells furnish material for the characteristic 
development of the others, and that the name 4 nutrient layer/ 
applied to them by Holfert (TO), is appropriate. The basal 
part of the palisade-layer, the walls of the sclereids in a slight 
degree, and especially the compressed nutrient layer, acquire 
during the ripening an increasingly dark brown colour, so that 
the ripe seed appears nearly or quite black to the naked eye. 
While the foregoing description applies to the body of the 
seed, there are some respects in which the structure of the 
coat at the micropylar end requires special discussion. When 
the seed is about half grown, the downward bend of the inner 
integument about the apex of the embryo-sac becomes longer 
and thinner, forming a sharp projection of the seed-coat into 
the perisperm, which may be termed the micropylar collar 
(m. c., Fig. 12). This peculiar collar, which we shall find to 
be very characteristic of the Scitamineae, differs slightly in 
