THE TETRANUCLEATE EMBRYO SAC OF CLINTONIA 
R. WILSON SMITH 
(WITH PLATE V) 
The following results are published in the belief that from the 
standpoint either of morphology or of phylogeny it is important 
we should become acquainted with the variations of the angio- 
sperm embryo sac. By searching out and comparing all deviations 
from the normal type, we may hope to ascertain the directions in 
which the embryo sac is varying at the present time, and perhaps 
we may also discover some clue to the path along which it has 
come. The results here given were obtained from a study of 
Clintonia borealis, collected in the neighborhood of Toronto and of 
Lake Joseph, Ontario. 
The youngest ovaries, collected May 9, showed the ovules 
already completely anatropous, each with a large archesporial 
cell, having its nucleus in the synapsis stage (fig. 1). The arche- 
sporial cell undergoes no cell division, neither cutting off a parietal 
cell nor dividing into megaspores, but, as in many liliaceous ovules, 
passes directely into the embryo sac. Its nucleus, however, 
suffers a twofold reducing division which is of considerable interest. 
The nucleus in the synapsis stage is very large; it is usually 
situated slightly below the middle of the cell, and occupies fully 
four-fifths of its width. In the condition represented in fig. 2, the 
protoplasm is becoming denser about the periphery of the nucleus 
in preparation for spindle formation, and the loops of chromatic 
material are beginning to separate and spread throughout the 
nuclear space. Subsequently, when the fibrils of the spindle are 
quite distinct, the chromatin is found segmented into chromosomes, 
which frequently appear in the x’s, y’s, and other forms, character- 
- istic of the heterotypic division. 
The number of these chromosome pairs I have not been able. 
to determine with certainty, since the nucleus is too large to be 
included. in one section. Further, since all my sections are cut 
209] [Botanical Gazette, vol. 52 
