TETRAD AND EMBRYO-sac MITOSES TT 
Pellia, by Davis,* in Asc/epzas,t by Strasburger, and in certain 
Liliaceae by Schniewind-Thies i has not been observed to 
_occur. 
From the facts above presented it will be seen that in Crucia- 
nella, as in Asperula, the first splitting of the chromosomes is longi- 
tudinal. In early anaphase the daughter rods which open out 
from a double V-form into rings, separate finally at the ends of the 
limbs of the V, the angles being directed toward the pole. Later 
a second longitudinal splitting appears, the formation of grand- 
daughter rods being completed before the close of the first mitosis. 
This division is, therefore, heterotypic and corresponds in essential 
details to the heterotypical mitosis in the spermatocytes of the 
salamander as described by Flemming. 
The final evidence for this conclusion in regard to the embryo- 
sac-mother-cell has not been obtained without any doubt, but I 
believe that we may conclude from the otherwise complete corre- 
spondence in the two cases that the first embryo-sac-mother-cell 
division is also heterotypic. 
The resting stage occurring between the first and second di- 
visions is characterized by its short duration, and by the varying 
degree of diffusion of the chromatin. This variation is considerable 
not only among related species, but is evident in comparing the 
pollen and embryo-sac tetrad divisions in the same plant, as 
Strasburger $ has observed to be the case in Lilium, It is notable 
that in the Rubiaceae alsothe daughter nuclei of the pollen mother- 
cell enter the resting stage less completely than in the corre- 
sponding nuclei in the ovule. If this prove to be generally true we 
may attribute the behavior to the closer analogy between the tetrad 
divisions in pollen and those of cryptogams, and the greater irregu- 
larity in the tetrad divisions in the ovule to the changed condi- 
tions which have been brought about in that organ. 
_ Although the variation in the character of the resting stage is 
* Davis, B. M. Nuclear Studies in Pelia. . Bot 15: 147. 
T Einige isn zu der Pollenbildung per Asclepias. Ber. deutsch. bot. 
Gesellsch. 19: 1901. 
D. Ps T. Die Reduction der Chromosomezahl und die ihr folgen- 
den Kerntheilungen in den Embryosacmutterzellen der Angiospe permen. Jena, 1901 
3 Ueber Cytoplasmastructuren, Kern und Zelltheilung. Jahrb. wiss. Bot. 10: 252. 
1897. 
