304 Iskikowa.—Shi dies on the Embryo Sac 
apparatus, secondary pole nucleus as well as antipodal nuclear group being 
present (Text-fig. IX, 5 and r, 2). The antipodals always acquire no 
separating walls, and sooner or later each nucleus becomes chromatic, 
assuming an irregular shape, and finally disintegrates as shown in Text- 
fig. IX, 6 a, 6 b. It is often the case that two antipodal nuclei do exist 
instead of three, or sometimes none, probably owing to an early disintegra¬ 
tion. This is no doubt a very interesting point, and deserves a close 
investigation. Thus, the result of the writer's investigation confirmed 
the report of Gibelli and Ferreo, except 
for the early stage in development. 
Therefore it seems not unreasonable to 
think that the present genus should be 
included in another distinct family, and 
it should not be regarded as representing 
an isolated group in the Onagraceae. 
This has already been suggested by 
Tackholm (68, 69 ), on account of its 
deviated morphological characters of 
the gametophyte as well as of the 
sporophyte. 
The morphological nature of the 
tetranucleate as well as 16-nucleate 
embryo sacs has been a subject of 
discussion by many investigators, and 
the prevailing opinion is to regard it as 
a modified form (Magnus ( 39 ), Fisher 
( 17 ), &c.). The following graphical re¬ 
presentation (Text-fig. XI), which was 
modified from the figures given by 
Fisher, Palm, and Dahlgren, would serve 
as a general sketch of the homology 
of all tetranucleate embryo sacs hitherto 
known to occur among the Angiosperms. 
As shown in the diagram, the embryo sacs of the Onagraceae, of 
Codiaeum , of Gastrodia , and of Clintonia are of a monosporic nature, and 
those of Dicraea , of Cypripedium , of Podostemon, of Hydrobium, and of 
Helosis are bisporic, while in Plumbagella it is really tetrasporic. If in the 
latter case the nuclei divide once more, the sac assumes the Lilium type\ if 
they divide twice, the sac acquires the type which comprises all known 
cases of the 16-nucleate embryo sacs. 
Nearly all the tetranucleate embryo sacs do not possess antipodals, but 
contain a single polar in each of them. As stated above, the axis of the 
spindles at the second division of the nucleus of the embryo sac cell are as 
Text-fig. X. Sagittal section of ovule, 
x 30. 1. Trapa natans ; 2. Trapa natans 
var. incisa. 
