The Ohio Naturalist. 
[Vol. VIII, No. 2, 
216 
Summary. 
1. The arehesporial cell of Asimina triloba remains un¬ 
differentiated during the winter, no differentiation being apparent 
until about April 14. 
2. Tetrad megaspores are of rather frequent occurrence. 
3. The parietal layer of the ovule develops greatly. 
4. The great elongation of the embryo sac is striking. 
5. The length of time that the polar nuclei remain in con¬ 
tact is quite unusual (three weeks and over). 
6. The evanescent condition of the antipodals is rather 
unexpected in this farm. 
7. The oospore remains undivided relatively long (between 
three and four weeks). 
8. Endosperm forms ih a peculiar manner. The first wall 
is transverse and divides the sac into two equal parts. The for¬ 
mation of a linear series of endosperm now follows, continuing 
until about a dozen cells are formed when a vertical division 
begins at the base of the sac. 
9. The embryo is minute and imperfectly developed, even 
in the seed. 
10. Comparatively few large microsporocytes are formed. 
11. There is a peculiar development of sterile tapetum-like 
tissue in the microsporocytes. 
12. The pollen grains are ready to be shed by May 5. 
13. The study shows that Asimina triloba differs in its 
development from the Ranunculaceae and Papaveraceae and, 
14. Resembles the Ceratophyllaceae more or less closely in 
its development. 
DESCRIPTION OF PLATES. 
All drawings were made with the use of the camera lucida at table dis¬ 
tance. A Bausch and Lomb microscope was used with the combination 
lenses indicated with each description. 
Fig. 1. —Sept 30, 1905. Cross section of ovulary showing undiffer¬ 
entiated ovules. B. & L. 1 in.-£ in. 
Fig. 2.—Jan. 6, 1906. Section of ovule showing undifferentiated con¬ 
dition still present at this date. B. & L. 1 in.-£ in. 
Fig. 3.-—April 14, 1906. Tip of ovule showing the differentiated 
arehesporial cell. B. & L. £ in.-£ in. 
Fig. 4.—April 21, 1906. Shows arehesporial cell divided into parietal 
cell and megasporocyte. The parietal cell is divided into two by a vertical 
wall. B. & L. J in.-4 in. 
Fig. 5. —April 21, 1906. Tip of ovule showing incipient integuments 
and further division of parietal layer. B. & L. 1 in.- T V in. oil immersion. 
Fig. 6.—April 28, 1906. Shows four megaspores arranged in a row; 
the three upper ones are dissolving. B. & L. £ in.-£ in. 
Fig. 7.—April 28, 1906 Shows extensive parietal tsisue and four 
megasporocytes, the two outer divided by a vertical wall. B. & L. J in.- 
i in. 
Fig. 8.—April 28, 1906. Same as Fig. 7. —Four megaspores, the two 
outer ones divided by a vertical wall. B. & L. £ in.-£ in. 
