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| 
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. 
1896.] Embryo-sac of Alisma., 125 
may be the homologue of the oosphere. These three nuclei 
are not surrounded by any definite cell-walls, but the cyto- 
plasm in which they are imbedded is rather dense. Immedi- 
ately beyond the antipodal cells is the lower polar nucleus. 
This is much the largest nucleus in the antipodal region, and 
it contains usually one large nucleolus. Its centrospheres lie 
on the upper side, toward the upper polar nucleus. 
Conjugation of the polar nuclei and their centrospheres. 
The two small granules lying on one side of the resting 
nucleus are now generally called controspheres by English 
writers, and this term is here employed as the most appro- 
priate. The dense centre is appropriately designated by the 
usual term “centrosome,” while ‘‘attraction-sphere” will be 
used for the hyaline layer surrounding this. 
I might here state that all my observations on these bodies 
favorable circumstances shows a delicate radiate structure. 
he whole structure is limited from the surrounding cytoplasm 
by @ definite granular layer, which is easily distinguished and 
ne Propriately be called a membrane. The centrospheres 
- re embryo-sac are much more prominent than in the sur- 
naa tissues, and in this respect they agree with the 
t As stated above, when the two polar nuclei begin to travel 
that ¢ each other, they have their centrospheres so ohare 
v they Precede the nuclei; however, in a few cases, at the 
JY beginning they were seen on the opposite side. _ In my 
of eations I was able to find all stages of the conjugation 
Nuc] © polar nuclei, until their complete union to form the 
Cleus of the embryo-sac, or definitive nucleus (figs. 3, 4, 5, 
ON the observations agree in general with those of Guigna 
. 
table Batre and distribution of attraction-spheres and centrosomes in vege- 
» Bor. Gaz., 19: 445-459. 1894. 
