Notes on the embryo-sac of Passiflora adenophylla 



Melville Thurston Cook 

 (with plate 19) 



While in Cuba, about two and a half years ago, the writer had 

 occasion to make a study of the characters of the embryo-sacs 

 and embryos of a number of tropical plants. While pursuing this 

 work attention was called to Passiflora ade^wphylla Mast."*" which 

 was growing luxuriantly in the botanical garden of the Agricul- 

 tural Experiment Station at Santiago de las Vegas. Unfortunately, 

 a sufficient amount of material for a complete study was not 

 secured before leaving the island. However, the facts brought 

 out by the study were so interesting that it has been considered 

 advisable to present them at this time. 



The early stages in the formation of the embryo-sac were not 

 observed. The four-nucleate stage (fig. i) did not vary from the 

 usual form. It was about twice as long as broad and the two 

 nuclei at the micropylar end were somewhat larger than the two 

 at the antipodal end. In the eight-nucleate stage (fig, 2) the sac 

 had elongated to about three times the length of the four-nucleate 

 sac and the antipodal half w^as considerably narrower than the 

 other half The egg was considerably larger than the two syn- 

 ergids, the antipodals were well defined and the two polar nuclei 

 unite near the egg (figs. 2 and 4). 



The pollen-tube is very prominent (figs. 3, 6, and 7) and the 

 two sperm-nuclei are clearly visible after their escape into the sac 

 (fig. 3), Double fertilization was very evident (figs. 4 and 5) and 

 was observed in a great many preparations. In fact the writer 

 has never examined plants in which double fertilization was so 

 conspicuous. 



However, the most interesting feature of this study was the 

 peculiar behavior of the pollen-tube, which, as previously stated, 

 w^as very prominent. In the majority of cases it does not dis- 

 charge its nuclei but continues its growth within the sac, eventually 



* Determined by Dr. J. N. Rose, of the National Museum, Washington, D. C, 

 where a specimen has been deposited- It is a native of Brazil, 



273 



