(351 ) 
About this time the ovule enters upon a very rapid period of 
growth, and the nucellus, no longer compact, is cleft by the 
endosperm, which extends toward the chalaza. The endo- 
sperm gradually assumes a cellular character, beginning in 
the region of the embryo. Only in the micropylar region is 
there any approach to compactness, most of the mass consist- 
ing of large thin-walled cells with small protoplasmic content. 
The first cleavages of the embryo are transverse and a row 
of cells is thus formed (fg. 67). The subsequent divisions, 
however are for some time irregular and result in the forma- 
tion of a globular mass of cells (jigs. 68-70), in which no dif- 
ferentiation beyond that of the epidermis is visible. A later 
stage was observed in figure 77 in which the cotyledons were 
being formed. In this case the differentiation into root-cap, 
periblem and plerome was well under way. At this stage 
the dimensions of the mature seed are approximately reached. 
Luffa 
When the undulations, which mark the origin of the ovules, 
become evident upon the surface of the placenta (see text- 
figure 5, H’) the groups of cells lying beneath the apex of each 
incipient ovule present a highly meristematic character. 
One of these cells soon appears larger than its neighbors and 
possessed of a very conspicuous nucleus. Sometimes there 
may be two such in an axial row, the outer one adjacent to 
the epidermis. The first indication of an archesporium is 
not always clear. Sometimes the spore-mother-cell itself 
appears in the hypodermal mass (fg. 72). In such a case it 
is quite conspicuous but no very definite tapetum is apparent. 
Subsequent divisions of the overlying cells, however, are 
mostly in periclinal planes (7g. 73). Thus a tier of several 
cells is formed above the sporogenous cell. The latter 
increases in size (fg. 74) until it becomes about two-fifths 
the length of the nucellus. 
The development of the ovule is rapid from the time when 
the first indication of the archesporium is apparent. When 
the spore-mother-cell is well differentiated (7g. 72) the ovule 
