The Morphology of Ruppia Maritima. 137 
and I have, therefore, no occasion to alter or .add to Murbeck’s 
excellent description. 
In brief, the changes are very similar to those which lead up to 
the first division in the pollen mother-cells. The megaspore mother- 
cell and its nucleus enlarge, while the latter goes through the 
synapsis and succeeding stages, the staining reactions being 
essentially the same and even the fine kinoplasmic fibers appearing 
in the cytoplasm the same as in the corresponding stages in the 
pollen mother-cell. 
In the spindle formed for the first reduction division, eight chromo- 
somes appear (Pl. XII, fig. 80), as Murbeck also announces in 
Ruppia rostellata. Although the chromosomes are here much thicker 
than in the sporophytic karyokinesis, they are nevertheless still so 
small that any definite declaration concerning their shapes and 
method of splitting is well nigh impossible. Still, as Murbeck has 
noted, the ring and Y-shaped forms characteristic of the heterotypic 
division are occasionally apparent. 
After the nucleus of the megaspore mother-cell has divided, we 
find a wall laid down separating the two daughter-cells (cf. Mur- 
beck, 1902, fig. 45). In this connection, reference might be made 
to the case already noted under the megasporangium (p. 136), where 
a double megaspore mother-cell was found. producing in each case 
two such daughter-cells (Pl. XI, fig. 78). 
The second division follows closely on the first, with a very slight 
pause, similarly as in the pollen mother-cells. The two walls re- 
sulting from these divisions are, however, laid down at quite different 
planes with respect to each other, that is, the wall dividing the 
two inner cells is periclinal, while that separating the two outer is 
anticlinal. Thus the two outer cells are both in contact with the 
third cell, and are separated by it from the innermost cell. The 
plane of the anticlinal wall is, however, obliquely situated with 
regard to the plane of a horizontal or vertical median section of 
the megasporangium; in other words, it is oblique to the plane of 
the paper on which such a section is represented, so that an ob- 
lique position of the two upper cells with respect to this plane 
results. 
This arrangement is shown by Murbeck (1902, pp. 13, 14, 
fig. 51). But often, due partly to the manner of cutting the section 
and partly to the orientation of the outer anticlinal wall, the pos- 
ition and even the number of cells is not so apparent, since one 
of the two upper cells then lies more or less completely over the 
other. Such a case is represented in PI. XI, fig. 79, which a hasty 
