3 
a 
1905] SHOEMAKER—HAMAMELIS VIRGINIANA 263 
end of the embryo sac as is found in Hamamelis, but here it persists 
into the ripe seed. The epidermal layer of the integument is not 
used up, and around the chalaza there is a small fragment of the 
nucellus left in the ripe séd. This is never stored with food mate- 
rials, and so cannot be called perisperm (fig. 28). The macrospore 
is buried about as deeply as in Hamamelis. It germinates only in 
the lower ovules, the upper ones never showing typical embryo sacs 
and being less developed progressively toward the top of the ovary. 
In the sterile ovules the cells of the outer integument become very 
much enlarged and at last empty. The substance of the nucellus 
is absorbed, and the ovules become polygonal bodies, resembling saw- 
dust, which fill the upper part of the ovary. The outer integument 
of the fertile ovule (fig. 28) grows into a wing. The embryo is 
Straight, and in bulk bears about the same relation to the endo- 
sperm as in Hamamelis. 
SUMMARY AND CONCLUSION. 
1. In Hamamelis the anthers have two microsporangia from the 
beginning. 
2. The generative cell in the pollen grain has a cell wall developed 
Which is afterward dissolved. 
3- The pollen tube when grown artificially shows a marked ten- 
dency to form cellulose plugs, and also forms spheres into which the 
Contents of the tube are withdrawn. Thus far these phenomena 
ave not been observed in normal growth. 
4. The development of the pollen tube in the style may be divided 
into three periods: first period of growth, hibernation, and second 
Period of growth. During hibernation the walls are thickened and 
the diameter of the tube enlarged, in the next stage having a 
smaller size and thinner walls. 
5 There are several macrospores developed, only one of which 
becomes functional. It is deeply buried in the nucellus by the growth 
of tapetal tissue. 
6. The germinating macrospore is nourished through a strand of 
conductive tissue from the chalaza. 
7- The antipodals are sunk in the tapering lower end of the 
embryo sac. This tip is surrounded by deeply staining tissue which 
for a time resists the dissolving action of the endosperm. 
