THE ENDOSPERM 183 



the data we possess. The phylogeny of the endosperm must be 

 traced, and the place of the polar fusion and of the triple fusion 

 in its history determined before opinions cease to differ as to 

 its morphological character. In view of such facts as we have, 

 however, we are inclined to hold with Strasburger that the 

 endosperm of Angiosperms is a gametophytic structure, and 

 that the polar fusion and the triple fusion are interpolations 

 in its history that do not change its essential character. The 

 fact that endosperm sometimes forms before fertilization indi- 

 cates that the triple fusion is not an essential prerequisite ; the 

 fact that endosperm forms without the polar fusion points at 

 least to the conclusion that it was once developed without it ; 

 the indifference of the male nucleus as to which polar nucleus 

 it fuses with (Lilium, Asclepias) does not show the selective 

 attraction connected with sex-fusion ; and the further fact that 

 when an undoubted fertilization occurs, whether of egg, of syn- 

 ergid, or of upper polar nucleus, an embryo is the result, indi- 

 cates that the presence of the male nucleus in triple fusion is of 

 subsidiary rather than of dominating importance. That the 

 fusing male nucleus does introduce parental characters that 

 manifest themselves in the endosperm is proved by the phenom- 

 enon of xenia, but this does not seem necessarily to prove the 

 sporophytic character of the endosperm. In fact, the develop- 

 ment and structure of the endosperm of Angiosperms is so much 

 like that of Gymnosperms that it seems easier to regard the 

 various fusions as merely resulting in a stimulus to growth than 

 to imagine a degenerate embryo assuming this particular de- 

 velopment and structure. Of course one might go to the ex- 

 treme, and regard the endosperm as neither gametophyte nor 

 sporophyte, but as a composite tissue involving both, but this 

 hardlv seems to be necessary. 



LITERATURE CITED 



1. Hofmeister. W. Neuere Beobachtungen iiber Embryobildung 



der Phanerogamen. Jalirb. Wiss. Bot. 1 : 82-188. pis. 7-10. 1858. 



2. . Xeue Beitriige zur Kenntniss der Embryobildung der 



Phanerogamen. Abhandl. Konigl. Sachs. Gesell. Wiss. 6: 533- 

 672. pZs. 1-27. 1859. 



3. Korxicke, F. Vorlaufige Mittheilungen iiber den Mais. Sitz- 



ungsb. Niederrh. Gesell. Nat. Heilk. Bonn. 1872. 



4. Strasburger, E. Zellbildungund Zelltheilung. Ed. 3. Jena. 1880. 



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