March, 1907.] The Embryology of Sagittaria lancifolia. 99 



nucleus but advanced the idea that it might "play an important 

 part in the transfer of food material from the funicular region, 

 beyond the antipodals, to the cotyledons, and especially in 

 facilitating the formation of the cap of endosperm which covers 

 the tip of the cotyledon." This idea has been supported by my 

 papers on the Nymphceacece* in which I found similar structures 

 and by Ikedaf, who demonstrated the antipodals to be in the 

 course of the food supply in certain species of Liliacece. In 5. 

 lancifolia I find further evidence in favor of this view; in many 

 instances the antipodals disappear and this part of the sac is 

 extended into a pocket-like structure (Fig. 3) in which we find a 

 mass of protoplasm extending to the lower endosperm cell. At 

 this time the embryo (Fig. 17) was well advanced. 



Embryo. 



Although the author did not secure the very youngest stages 

 of the embryo, after examining a large number, it seemed evi- 

 dent that the embryo had followed exactly the same line of 

 development as the embryo of 5. variabilis. The elongation of 

 the embryo was due to the repeated division of the cell next to 

 the suspensor. By the time tour cells in addition to the large 

 suspensor cell had been formed, the apical cell divided by the 

 formation of a longitudinal wall (Figs. 5, 6). After this the 

 longitudinal divisions were found to be somewhat irregular 

 (Figs. 7 to 16). The longitudinal cell walls were frequently very 

 indistinct but the number of cells could be ascertained by count- 

 ing the^ nuclei of the serial sections. My material was unsatis- 

 factory'for making a study of the more advanced stages of the 

 embryo but it apparently followed the same course of develop- 

 ment as 5. variabilis. 



From the facts herein presented it appears that the internal 

 and external characters do not necessarily co-ordinate. In the 



case of Nymphcsa advena of the north and the Nymphcsa 



of Cuba which so far as external characters are concerned are 

 strikingly similar the embryos show considerable differences, 

 while in the case of S. variabilis and 5. lancifolia the external 

 characters are strikingly different and the embryological char- 

 acters are practically the same. But we are now confronted by a 

 new question which can only be answered by future investiga- 

 tions: Are the embryological characters of the plant more or less 

 plastic than the external characters? 



* The development of the Embryo-sacs and Embryos of Castalia 

 odorata and Nymphsea advena. Bull. Torr. Bot. Club. 24: 211-220. 



t Ikeda, T. — Studies in the Physiological Functions of the antipodals 

 and Related Phenomena of Fertilization in LiliaccEe. I. Trycirtis hirta 

 Bull. Coll. Agri. Tokyo Imp. University. 5: 41-72. 1902. 



