Development of Cassytha filtformis, L. 403 
ening takes place to a considerable extent throughout, but 
continues very rapidly at the upper end, so that in the ripe 
fruit a great cap of dense cellulose covers the upper end, four 
times the thickness of the cap produced by the inner layer 
of mesocarp. The cells have now become exceedingly nar- 
row, with faint, disintegrating nuclei in the middle, the rest 
of the cell being filled with cellulose. While the inner meso- 
carp cells are usually quite brown in color, the endocarp is 
lemon yellow. These two layers, particularly the inner, 
invest the soft parts beneath with an armor of cellulose, 
which must be an excellent protection from all ordinary 
mechanical dangers. The only interruption to this is the 
minute aperture of the micropyle, which is filled with cellular 
tissue that will be referred to again. This aperture at the 
upper end has the radicle of the embryo extending vertically 
down from it and lying with the thicker or radicular end 
toward it, as shown in Fig. 2. 
Internal to the horny cap is the outer indusial layer. It 
shows rather large columnar cells, very delicate-walled and 
empty (9). It fades out toward the micropyle. Within it, 
in a lateral position and almost or quite absent at the two 
poles, are several layers of loose, thin-walled empty cells 
(10), the tegmen. By the growth of the embryo these are 
crowded and partially absorbed until they leave only an 
irregular thin lamellated layer pressed close to the testa. 
Next to the embryo, and separated from it by a mere base- 
ment membrane, is a series of obliquely placed spiral cells 
(11). These seem to form a very copious raphe and com- 
pletely enclose the embryo. In the ripe seed they become 
narrowed toward the base. At the micropylar end they give 
way to a strand of fibrous tissue, which completely plugs up 
the end of the micropyle left by the fruit and seed coats. 
This strand extends down one side through the middle of the 
cellular tissue of the sorus. It is directly continuous with 
the style of the flower. 
The embryo in the ripe seed is a globular yellow body 
