WEATHERWAX: SPIKELETS OF ZEA. Mays 491 
hairs arranged in definite areas... Each hair has its origin in a single 
epidermal cell (see TExt-FIGs. 17-24) which divides anticlinally, 
giving rise to four, or occasionally five, cells. Each of these cells 
divides transversely a num- , 
ber of times and produces 
a long filament, the four 
filaments being loosely at- 
tached to each other, leav- 
ing an intercellular canal 
in the middle of the hair. 
Some of the filaments are . 
longer than others, and, as A/S 
a result, the hair tapers to r i 7) 
a point, where it consists } 
of but a single cell or a “y 22 
single row of cells. The 
upper ends of many cells of 
the hair are turned out- 
ward, giving the pollen tube 
easy access to the canal in . 
the middle (TExT-FIG. 25), 2 21 
through which the tube Fics. 17-24. Steps in the development of 
stigma hair. Fics 25 and 26. Cross sec- 
reaches the main part of 
the silk. It seems that it 
is only through these hairs that the pollen tube can gain entrance. 
The ovary contains a single ovule, which is of a modified campy- 
lotropous form. At about the time of the differentiation of the 
megaspore mother cell, the integuments begin to grow up around 
the nucellus. The tissues on the adaxial side of the ovule grow 
so much faster than those on the other side that, at time of the 
maturity of the embryo sac, that organ, with the tissue immedi- 
ately surrounding it, has been completely inverted. The ovule 
is attached for a considerable distance along one side, and no 
funiculus is present; the embryo sac remains straight, as does the 
developing embryo. The one part of the outer integument seldom 
grows further than the top of the ovary, where it forms a folded or 
wedge-shaped body, closing the stylar canal (TEXT-FIGS. 27, 28). 
The micropyle is formed by the inner integument, and the 
nucellus protrudes through it (TEXT-FIG. 29). 
23 
0) 
a 
tions of stigma hairs, X 200. 
