1905] SHATTUCK—ULMUS AMERICANA 215 
of three polar nuclei fusing in Ulmus and I have frequently observed 
three or four nuclei in contact and evidently preparing to fuse (figs. 
58-59). Several cases were found where a well formed egg appeared 
in the antipodal end of the sac (figs. 36, 50, 54, 56). Notwithstand- 
ing the fact that in each of these cases the structures seemed to be 
normal eggs in every particular, I hesitated to adopt this interpreta- 
tion until later, when embryos were discovered in the antipodal ends 
of two sacs, and in each of which a larger and older embryo appeared 
in the micropylar end (figs. 51-52). These antipodal embryos are 
wholly within the sac and I do not think they were produced 
apogamously. 
In 1895 CHAMBERLAIN (5) found in Aster novae-angliae what he 
termed an antipodal oosphere, calling attention to its cytological 
resemblances to the ordinary oosphere, and stating that ‘“‘we need 
only fertilization and the formation of an embryo to completely 
establish its right to the name.” 
Lately Miss OppERMANN (17) has found an antipodal egg in 
Aster undulatus, with the sperm lying against the cytoplasm of the 
egg, thus proving that fertilization does actually occur. 
‘TRETJAKOW (19) has found the antipodal embryo which, since 
Miss OPpPERMANN’s discovery we are justified in concluding comes 
from a fertilized antipodal egg, thus making the history complete 
and establishing beyond a reasonable doubt the right to call this - 
structure an egg. As the conditions mentioned above were all found 
in Ulmus, I feel justified in calling these antipodal structures eggs. 
There are two well formed synergids which enlarge nearly to the size 
of the egg. One of these usually disappears about the time the pol- 
len tube enters the sac. The other generally persists until after the 
fist division of the egg. 
The polar nuclei were never found actually fusing, though they 
Were often found in close contact (fig. 33), in which condition they 
seem to remain for some time. 
Wwi1e (21) has shown that in Elodea the actual presence of the 
ea in the ovule is necessary in order to stimulate fusion. 
ae "a So has arrived at the same conclusion in regard to 
bas oa find that the polar nuclei of Ul/mus americana behave 
€ manner, fusion occurring at least before fertilization. 
