2 
Sac cael RR ce em SOR ee a eee ae ee eee 
5 3 ‘ ae . * 
3 ‘ 
1897] THE LIFE HISTORY OF SAGITTARIA VARIABILIS 257 
bulging of the female nucleus toward the male nucleus has also 
been observed in Pinus Banksiana and P. Laricto.3 In the case of 
the large female nucleus of Pinus, however, the bulging appears 
only as a papilla-like protuberance, while in Alisma and Sagit- 
taria the whole side of the nucleus appears to be drawn out. 
What the physiological significance of this bulging is cannot be 
stated, but it seems to be one of the characteristic phenomena 
of fertilization in the higher plants. 
Although the method of staining employed did not bring out 
the centrospheres of the oosphere nucleus as readily as those of 
the sperm nucleus, they were sometimes seen, and when they 
appeared they were found lying just beyond the bulge of the 
oosphere nucleus toward the sperm nucleus (fg. 27). Thus, 
during the approach of the two sexual nuclei each one is pre- 
ceded by its two centrospheres. Just before the contact of the 
sexual nuclei, two pairs of centrospheres appear on opposite sides 
of the approaching nuclei (fig. 30), and when the nuclei are in 
contact a little later, the two pairs appear to be fusing (fig. 37). 
These appearances are the same as those I observed during the 
fusion of the polar nuclei of Alisma, and seem to point strongly 
to a pairing and subsequent fusion of the four centrospheres 
which are thus brought together. Although these appearances 
very properly can receive such an explanation, it must be borne 
in mind that other movements and other explanations are pos- 
sible. Thus, the two centrospheres which appear on the upper 
side in figs. 30 and 37 may be interpreted as belonging to the 
female nucleus, while the lower pair may have come from the 
male. This would do away with the so-called “quadrille 
movement.’’ I think, however, that Guignard’s explanation of a 
conjugation in pairs is the more reasonable one, from the fact 
that during fusion of cells not only the nuclei themselves fuse, — 
but apparently also the cytoplasm, chromatophores, and pyre- 
noids, indicating that during fusion all protoplasmic bodies of 
the same nature in the cells are involved in the act. The evi- 
dence which led me to infer a a of se during 
3 Bor. Gaz. 23: 40, 41. 1897. 
