312 
Is hik aw a,—Studies on the Embryo Sac 
Ecological Consideration of Tetranucleate Embryo Sac. 
Of the papers dealing with ecological consideration of the tetra¬ 
nucleate embryo sac, those by Magnus ( 39 ) and by Kusano ( 36 ) seem to be 
the only ones in which the authors try to explain the origin of the modified 
embryo sac in detail. According to the former investigator, the feeble 
reproductive part of the Podostemaceae lifts itself above water at the 
flowering time, and becomes exposed to the direct sunlight of the Tropics. 
It is therefore subjected to a xerophytic condition under which, and within 
only a few days’ time, the gametophytic part of the life cycle should be com¬ 
pleted. Thus, an abbreviation of certain processes in the gametophyte and 
some amount of modification in the nucellar tissues are necessarily brought 
about by pressing need for a rapid growth. Kusano states that in Gastrodia , 
as the reproductive organs develop at the expense of the food material 
stored in the subterranean tuber alone, the nutritive substance must be 
economically distributed to the organs, especially because of the great 
rapidity of growth of the flower shoot, gametophyte, and the fruit. Thus, 
he attributes the origin of the abbreviation of the sac to the extreme 
restriction of the food and time, and concludes that the physiological 
adaptation in the gametophyte has brought forth morphological adaptation. 
And, according to him, the embryo is fed for a time with nourishment in the 
sporophytic tissue, as is the case with the Podostemaceae. However, in the 
case of Oenothera and other genera of the Onagraceae there is no such 
pressing ecological condition which can explain the occurrence of the 
aberrant embryo sac. Nor does any morphological or physiological devia¬ 
tion happen in the ovular tissues, although a curious relation exists between 
the hypostase and starch grains, which apparently has nothing to do with 
the tetranucleate gametophyte and development of the embryo. Thus, 
the writer is led to the conclusion that the tetranucleate condition of the 
gametophyte of the Onagraceae was caused by mutation, but the subsequent t 
physiological counterbalance was not so markedly disturbed, that it became 
fixed without any special modification of the surrounding tissues. 
Additional Note. 
Among the tetranucleate embryo sacs of the Onagraceae examined by 
the writer, those of Godetia are the largest, while those of Ludwigia are the 
smallest. The sac of Gaura comes next to that of Godetia , then follow 
those of Epilobium , Oenothera , Circaea , and Jussieua, as shown in Text-fig. 
VIII, i—12. In Text-fig. VIII, 9 a, 9 b, 9 e, three successive sections of three 
developed embryo sacs are shown, which especially are worth mentioning; 
if they are reconstructed, three mature sacs, which are arranged in an axial 
row, are obtained. Judging from the remnants of the tapetal cells, the 
