1904] LAND—EPHEDRA TRIFURCA 9 
slit a short distance down one side (fig. 44). The pollen enters the 
open end of the integument, and drops down to the bottom of the 
pollen chamber (fig. 44), where it lies in contact with the archegonial 
end of the female gametophyte. So far as known, there is no other 
gymnosperm in which the pollen grain is placed so near the arche- 
gonia. 
The archesporium could not be traced definitely back to a single 
hypodermal cell, but there are indications that such may be its 
origin. The earliest stage in which a suggestion of differentiation was 
observed is shown in fig. 26, March 8, 1903. The lower larger cell 
in this figure is beyond doubt the megaspore mother-cell. The large 
cell above will divide again and again, and thus place the megaspore 
mother-cell deeply within the nucellus. In jig. 27 the divisions of a 
similar cell are clearly apparent, and the conspicuous megaspore 
mother-cell is shown. In general not more than one megaspore 
mother-cell is organized, but instances were noted in which two 
and very rarely three mother-cells were present. Sometimes, but 
not always, each of these cells produce megaspores. In general one 
mother-cell soon gains an advantage over the others and causes their 
rapid disintegration. 
The mother-cell grows rapidly, meanwhile encroaching on the 
surrounding nucellar tissue. The reduction division occurred about 
March 8, 1903 (fig. 28). The second division quickly follows the 
first, and the more deeply placed megaspore alone functions. Accord- 
ing to both Strasburger and Jaccard, three megaspores only are pro- 
duced in the forms studied by them. In E. érijurca either three or 
four may occur (figs. 29, 30). In many instances the upper cell does 
not divide; again, the division may be incomplete, or it may be 
completed entirely. In no observed instance does the division of 
the upper cell take place until two lower megaspores are entirely 
separated; fig. 29 shows such a late division of the upper cell. It 
seems that the more deeply placed cell because of its relation to the 
food supply is enabled to divide first. From this it follows that the 
most favorably placed megaspore—the lower one—is enabled to grow 
so rapidly as to preclude much further development on the part of the 
others. The megaspore remains a very short time in the resting con- 
dition. The number of chromosomes at the reduction division is 
