120 Smith on Structure and Parasitism 
Plate XV, Fig. 4, shows the stage immediately following. 
The egg has divided longitudinally, and the suspensor consists 
of four cells. The lowest of these is destined to become the 
hypophysis of the future embryo. 
In Fig. 5 the egg has divided into octants, and the hypophysis 
is plainly marked. The suspensor is still four-celled. The 
endosperm has increased greatly in bulk, and numerous small 
starch grains are found in its cells. 
Fig. 6, of Plate XV, illustrates an almost mature seed. 
The integuments have become thin and flattened, and the endo- 
sperm contains much starch. The embryo has attained its 
full development. The regions are not clearly marked out, 
but the hypophysis here shows only anticlinal divisions. This 
is in harmony with Koch’s statement that the primary root 
forms no root-cap. 
SUMMARY. 
1. Aphyllon uniflorum is parasitic on Aster corymbosum. 
The degeneration attendant upon its parasitic habit is expressed 
by: 
(a) Absence of chlorophyl. 
(2) Degeneration of bract-leaves. 
(c) Loss of root-hairs. 
(2) Reduction of the bundle-system, and the greater 
relative development of phloem than of xylem. 
(e) Small size of seed and primitive embryo, and the 
development of this embryo within a mass of pre- 
cocious endosperm which completely surrounds 
the embryo and suspensor. 
2. Parasitic roots form intimate connections with host-roots, 
but the host-roots are not entirely starved beyond the point 
of attachment. 
3. Stomata are present on bract-leaves, flower-stalk, calyx 
and corolla. 
