LIFE HISTORY OF PINUS 137 



It has been held by various students that all the nuclei in the 

 embryo-sac of Angiosperms are potential eggs. Murbeck ('01) 

 has recently, as recorded by Overton ('02), demonstrated the 

 development of an embryo inAlckemella; Chamberlain ('95) dis- 

 covered the presence of an antipodal oosphere in Aster ; -and 

 many earlier investigators have made similar observations regard- 

 ing the synergids and antipodals. 1 The discovery of archegonia 

 that have originated not only from superficial cells at the top and 

 along the sides of the prothallium, but from cells considerably 

 removed from the surface as well would seem to give direct 

 affirmation to the suggestion made by Atkinson ('01) that all the 

 cells of the prothallium in Gymnosperms are potential eggs. 



Among the many archegonia studied, I have found two in 

 which the nucleus of the ventral canal-cell approximated that 

 of the egg in size. Fig. 268 shows such a condition in Pinus 

 Strobus, but even here the nucleus of the ventral canal-cell is 

 much smaller than that of the egg. It is, however, remarkably 

 large for the nucleus of the canal-cell in this species, and is 

 apparently still in a normal condition, whereas this nucleus is 

 ordinarilly in an advanced stage of disintegration when the egg 

 has reached maturity. A much more marked increase in the 

 size of the nucleus of the canal-cell has been observed in Pinus 

 austriaca as illustrated in fig. 269. Here it has attained a com- 

 paratively enormous size and presents almost exactly the same 

 structure as the nucleus of the fully developed egg, though 

 slightly smaller than the egg-nucleus. Chamberlain ('99) fig- 

 ures a similar enlargement of the nucleus of the ventral canal- 

 cell in Pinus Laricio and concludes that this cell is the homo- 

 logue of the egg. It will be noted that in the instances described 

 above, no ventral canal-cell has been formed, but that in both 

 cases the nucleus of the canal-cell lies free in the cytoplasm of 

 the egg 2 (figs. 268, 269). The failure to form a wall cutting 

 off the ventral canal-cell from the egg, or the early absorption 

 of this wall if it has been formed, seems to me ample reason 

 for the unusual size and persistence of the nucleus of the canal- 



1 Miss Opperman, a student in my own laboratory, has recently discovered the 

 fertilization of an antipodal egg in Aster, a description of which is soon to be 

 published. 2 



2 See note at close of Appendix. 



Proc. Wash. Acad. Sci., September, 1904. 



