ANDERSON: EMBRYOGENY OF MARTYNIA LOUISIANA 153 
division of one of the three normal ones. FIG. 34, a cross section 
of the chalazal end of an embryo-sac in the same stage as the 
above, shows the arrangement of the four antipodals. At this 
stage, the nuclei of the antipodals appear as densely staining 
homogeneous masses. 
As the embryo with its very long suspensor grows through 
the center of the elongating embryo-sac, large endosperm cells 
rich in cytoplasm are formed, but when it reaches the lower 
part of the sac where the first division of the embryo takes 
place, the endosperm growth practically ceases in the middle 
and upper part of the sac. The cells of this part of the sac are 
rather large and similar in shape to those first formed, while 
those in the lower part are smaller and not so rich in cytoplasm 
(FIG. 35). It is also seen from Fic. 35 that the embryo-sac has 
enlarged considerably, especially the lower part which contains 
the developing embryo. The nutritive jacket is still very active 
in the elaboration of food for the growing endosperm. FIG. 36 
shows in outline the relative size of the embryo, endosperm and 
integument at the time the embryo is in the two-cell stage as 
seen in FIG. 35. 
THE EMBRYO 
After fertilization, the egg with its nucleus occupying a 
nearly central position in the lower part of the cell grows rapidly 
in length (Fic. 33). Its manner of growth down through the 
endosperm is similar to that of a pollen tube, for it becomes a 
long narrow cell with the nucleus retaining a position near the 
growing tip. No division seems to take place until the distal 
end has transversed nearly two thirds the length of the embryo- 
sac. The lower portion of the cell is rather dense in cytoplasm 
and stains deeply, but the upper portion has very little and 
stains so faintly that the course of its growth is hard to trace. 
After the distal end has reached the lower portion of the 
embryo-sac, a transverse division occurs, which forms a very long, 
slender suspensor cell and a short, rounded distal one, the em- 
bryonal cell (Fic. 37). In most instances the cytoplasm of the 
embyonal cell contains many plastids and other densely staining 
granules, while that of the suspensor is very poor in plastids. 
After the first division two others occur almost simultaneously. 
The suspensor cell divides, forming a short cell next the embryo- 
nal cell, which has enlarged preparatory to division, and, at the 
