302 
Ishikawa—Studies on the Embryo Sac 
E. Doaonaei 
Modilewski 1909 
Circaea Lutetiana 
C. quadrisulcata 
Oenothera biennis 
Oe. Lamarckiana 
Oe. rhizocarpa 
Oe. tetraptera 
Oe. coccinea 
Oe. nutans 
Oe. pycnocarpa 
Godetia sp. 
G. gloriosa 
G. Whitneyi 
G. amoena 
Gaura Lindheimeri 
G. parvifiora 
Ludwigia prostrata 
Jussieua repens 
J. villosa 
y. suffruticosa 
Podostemaceae : 
Podostemon subulatus 
Hydrobiuni olivaceum 
Farmeria nietzgerioides 
Balanophoraceae: 
Helosis guayanensis 
Euphorbiaceae : 
Codiaeum sp. 
Ceramanthus sp. 
Urticaceae: 
Elastostemma acuminatum (in some cases) 
W erner 
1914 
Ishikawa 
I 9 1 5 
Modilewski 
1909 
Werner 
J 9 1 4 
Renner 
Geerts 
1909 
Werner 
1914 
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Chodat et Bernard 
1900 
Arnoldi 
1912 
>> 
Strasburger 1910 
Thus, it may not be unreasonable to assume that all the genera of the 
Onograceae are provided with a tetranucleate embryo sac except one 
deviated genus, Trapa , which has been reported by Gibelli and Ferreo ( 22 ), 
working on Trapa natans , as having a normal 8-nucleate embryo sac. 
According to those investigators the embryo sac of Trapa natans directly 
develops from a mother-cell just as in the case in Lilinm . As their paper was 
published so long ago as 1891, these results require a re-investigation, and 
it is much to be desired to undertake it inasmuch as the present genus 
has been put into different families by different authors. 1 
It was therefore thought advisable to examine Trapa natans and 
its var. incisa . Although the material was not quite sufficient for tracing 
whole developmental stages, yet two essential points were clearly made out. 
The embryo sac mother-cell forms a tetrad due to the reduction division 
as shown in Text-fig. IX, 2, 3, and the chalazal megaspore develops 
the embryo sac (3, 4). The mature embryo sac is very slender, 
slightly recurved, tapering upwards, and provided with a normal egg 
1 For instance, in Onagraceae by Bentham and Hooker; treated as an appendix to the 
Onagraceae by Eichler; included in Hydrocaryaceae by Raiman in Engler’s Pflanzenfamilien; 
reunited into Oenotheraceae by Engler in Syll. der Pflanzenfam. (ed. 8) ; and treated even as an 
isolated member of Halorrhagidaceae by Endlicher, Lindley, Parmentier ( 54 ), &c. 
