1909] MCALLISTER—EMBRYO SAC OF SMILACINA 205 
confronted with a series of changes leading to a method of embryo 
sac formation quite different from any which has been hitherto 
described. 
The cell walls which separate the four megaspores break down 
and disappear. Immediately following the formation of four fully 
separated daughter cells and nuclei (figs. 8, rz) we find a stage in 
which the same four nuclei are seen occupying a large cell with no 
traces of cell walls separating them (fig. 14). The evidence of the 
disappearance of the walls between the megaspores is not based on 
scattered examples, selected from a large number of specimens, but 
on a large number of continuous series of stages taken from a single 
inflorescence. 
Fig. 11 shows four cells fully separated by cell walls, while in the 
next older flower on the same shoot are found four nuclei in a common 
cavity (fig. 14). In fig. 13 the cell walls formed by the second or 
homeotypic division have entirely disappeared, while a slight but 
distinct cleft, extending across the cell, shows the location of the wall 
formed between the nuclei in the first division. 
A statistical examination of a number of racemes to determine 
the exact stage of development of the mother cell or its products in 
each ovule, gave very conclusive evidence of the continuity of these 
series. The following is a fair example of an average shoot of the 
proper age. In this shoot of nine flowers the youngest flower had 
mother cells in a stage later than synapsis. The next older flower 
contained mother cells in the prophase and metaphase stages of the 
first division. The third showed in one ovule a heterotypic anaphase 
stage, and the other ovules showed the heterotypic telophase snide 
The fourth flower showed the earlier stages of the second or homeotypic 
division. The fifth contained daughter nuclei of the second division 
In the telophase stage, and the sixth showed nuclei of this division 
Separated by cell walls. The next older flower showed in a part of 
ts ovules the four nuclei still separated by cell walls, while the rest 
of its ovules showed little or no trace of cell walls between the four 
nuclei. The ninth flower, the oldest on the raceme, showed four- 
celled embryo sacs in all its ovules, with no traces of cell wall separat- 
ing the nuclei. The series here described shows no trace of the 
Stowth of one megaspore at the expense of the other three, or of the 
