Studies on the Embryo Sac and Fertilization in 
Oenothera. 
BY 
M. ISHIKAWA, RIGAKUSHI, 
Botanical Institute, Tokyo Imperial University , Japan. 
With Plate VII and fourteen Figures in the Text. 
T HE present paper deals with the behaviour of the gametophytes and 
fertilization phenomena in Oenothera nutans and Oe. pycnocarpa as 
well as their hybrids ; these two species were formerly included in Oenothera 
biennis until Atkinson and Bartlett ( 2 ) separated them as distinct species. 
The materials were collected during the summers of 1911 and 1912 in the 
Botanic Garden of the Cornell University, Ithaca, New York, U.S.A., 
where this work was commenced, and after the writer’s return to Japan 
the work was carried out in the Botanical Institute of the Tokyo University, 
and completed in 1915. 
The embryo sac and fertilization phenomena of Oenothera were already 
studied by Hofmeister so long ago as 1847 ( 26 ), but he could not so fully 
make out detailed structures of the embryo sac as we do now. He 
published, however, a figure of tetranucleate embryo sac of Godetia 
rubicunda , a closely related species, and later in 1849 he gave a full descrip¬ 
tion thereof ( 27 ). The investigations, to which the modern cytological 
methods were applied, are of comparatively recent date. In 1908 Geerts 
(20) published a brief account of the development of the embryo sac and 
fertilization in Oenothera L amarckiana, wh\c\i was followed by a detailed paper 
which appeared in the next year ( 21 ). On the other hand, Modilewski ( 42 ) 
independently studied the same subject, and concisely described various 
cytological features observed not only in Oe. biennis , but also in some other 
plants belonging to the Onagraceae. The results obtained by these two 
investigators agreed in the essential points that the embryo sac is tetra¬ 
nucleate, and that one pole nucleus and the whole antipodal apparatus are 
absent. Renner ( 55 ) was the third who made a careful study of the embryo 
sac, fertilization, and subsequent nuclear divisions in Oenothera biennis , 
Oe. Lamarckiana , Oe. muricata , as well as their hybrids, and made some 
additional contributions, besides affirming the absence of the melogony 
[Annals of Botany, Vol. XXXII No. CXXVI. April, 1918.] 
