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1900] DEVELOPMENT OF THE EMBRYO-SAC 43 
and more or less completely joined to it. The most plausible 
explanation for this seems to be that the segmentation for both 
divisions was nearly or quite completed before the formation of 
the first spindle, and that when they appeared on the nuclear- 
plate of the second spindle the segments had come together in 
pairs only to be separated again on going to the poles. No true 
resting stage seems to intervene between the two divisions. The 
above results are especially interesting, since three for the 
reduced number of chromosomes is one of the smallest so far 
found in plants. The later divisions in the embryo-sac were 
not observed. The spindle seems to be formed simply by the 
elongation of the kinoplasmic mass, no multipolar condition 
being noticed, and the mature spindle is long and slender but 
usually with obtuse poles. After each division a distinct mem- 
brane is deposited at the cell-plate, thus forming the axial row 
of four cells. The resting nuclei often show very distinct 
radiations from the nuclear membrane; especially is this the 
case with the lower one which now commences another period 
of growth before division in the embryo-sac. 
SUMMARY. 
Convallaria—The hypodermal cell divides into an upper and 
a lower cell, of which the inner cell becomes the archesporium 
and the upper forms part of the wall. This is also the case in 
Potamogeton and Canna. 
The stages of the growth and development of the archespo- 
rial nucleus are identical with those of the nuclei of the micro- 
sporangial archesporium. 
The first division of the archesporial nucleus is the hetero- 
typic division and corresponds to the first pollen-mother cell 
division in every respect. — 
The two spindles accompanying the second division are 
formed simultaneously. In appearance this division is identical 
with the second pollen-mother cell division and quite different 
from either the vegetative or heterotypic. A transverse division 
of the chromosomes could not be demonstrated. 
