io Humphrey . — The Development of the 
The seed-coat or testa is developed from both integuments 
of the ovule and from the layers of the chalaza into which 
the integuments pass at their bases. The inner integument 
is, at the time of fertilization, of a nearly uniform thickness. 
The micropylar portion lying above the apex of the embryo- 
sac becomes soon thereafter so overgrown and pressed together 
by the outer integument that the micropyle is tightly closed 
(m., Fig. 6) ; and with continued growth it becomes less and less 
easily recognizable (m., Fig. 10) until finally it can be identified 
only by comparison with earlier stages. When the young seed 
has reached a length of about 1-25 mm., there begins an unequal 
growth in the region of the base of the nucellus which results 
in an upward turning of the lower end of the inner integument 
(Fig. 6), heretofore directed downward. This bend becomes 
more and more pronounced, though but a small part of the 
integument is involved. When the seed is about 3 mm. long, 
there begins in the chalazal tissue the differentiation of 
a double cell-layer abutting directly upon the end of the 
inner integument and bending downward around the seed at 
a uniform distance from the surface and just within the 
vascular bundle (eh. i. i., Figs. 8, 16). Thus what may be 
called the outer and inner coats of the chalaza are marked 
off ; and, as they are in unbroken connexion with the original 
integuments, the subsequent differentiation of the whole testa 
proceeds uniformly. The discrimination of that part of the 
adult testa which is formed from the true integuments from 
that part developed from the chalazal coats is possible only 
by the study of its development. The inner integument 
forms in the ripe seed the internal tissue of the testa, con- 
sisting of two rows of large, empty, thin-walled cells, those 
of the inner row with colourless walls, while those of the outer 
row have amber-coloured membranes (eh. i. i., Fig. 19). The 
outer integument of the chalaza is twelve or fifteen cells in 
thickness. The outer layer is composed, from the first, of 
cells slightly elongated at right angles to the surface (ext., 
Fig- 15 a )- As the seed grows these cells continue to 
elongate, forming a palisade-layer ; and when the adult size 
