Nichols, A morphological study of Junvperus communis var. depressa. 221 
to lie about the peripbery of the young embryo sac, which 
begins to enlarge and within tbree days has increased in 
Yolume about twenty-five times (fig. 71). In tbe embryo sac re- 
presented by tbis figure sixteen free nuclei were £ounted. Tbe 
growth of tbe female gametopbyte now proceeds rapidly, while 
nuclear divisions continue to take place simultaneously, and by 
May 25 th , just previous to tbe formation of cellular tissue, its 
Volumetrie ratio, as compared with tbat of tbe megaspore at tbe 
time of tbe first nuclear division, is about 12 500: 1. Tbe embryo 
sac bas assumed tbe form of a prolate spheroid, tbe longitudinal 
axis of wbicb measures about 1400 /u. A figure of tbe entire cell 
at tbe time of wall formation. if drawn to tbe same scale as 
figs. 68, 70, and 71, would be 1.5 m. in lengtb. Fig. 72 represents 
probably the last free nuclear division, and in tbis preparation not 
only are all of tbe nuclei undergoing division, but all are in tbe 
same pbase of mitosis. Tbe axes of tbe spindles are for tbe most 
part parallel witb tbe major axis of tbe embryo sac. No attempt 
was made to count tbe number of nuclei present after tbe last 
free division. Tbe number bas been variously estimated in different 
gymnosperms. Miss Ferguson (1904) writes tbat “about 2000 
bave been counted in Pinus Strobus at tbe time wben tbe nuclei 
are being separated by tbe development of dividing walls 1 ’, and 
according to Noren (1907) tbe number in J. communis appears 
to be scarcely smaller. Growtb still continues after tbe formation 
of prothallial tissue, and at tbe time of fertilization tbe female 
gametopbyte bas acquired a lengtb of fully 2800 
Tbe manner in wbicb tbe cell tissue of tbe prothallium is 
organized agrees closely for tbe most part witb tbe observations 
of Mlle. Sokolowa (1890) and Noren (1907) to wbicb reference 
bas already been made. Immediately after tbe last free nuclear 
division delicate anticlinal walls are laid down separating tbe 
nuclei, but no periclinal walls are formed, so tbat tbe cells “appear 
as uncovered boxes, tbe opening extending toward tbe center of 
tbe prothallial cavity” (Ferguson 1904). Wben viewed from their 
inner, open ends tbe cells appear as in fig. 75. Their nuclei lie 
slightly below tbe free inner margins of tbe walls, and from tbem 
arise delicate Strands of cytoplasm wbicb radiate toward the free 
edges of tbe walls. An optical section tbrougb tbe nucleus and 
parallel to tbe megaspore membrane (fig. 76) sbows tbat tbese 
radiations are restricted to tbe open ends of tbe cells, tbe re- 
mainder of tbe cell cavity being intersected by coarser Strands of 
cytoplasm. Tbis relationship is even more clearly brought out in 
a radial section (fig. 74). Here it is seen tbat tbe outermost 
fibrillae are continuous from one nucleus to tbe next. As tbe walls 
are secreted tbese strands advance (fig. 7 7), so tbat, up to the 
time wben tbe inner ends of tbe tube-bke cells become closed in, 
all tbe nficlei of tbe embryo sac are connected witb one another 
by kinoplasmic fibrils. 
According to Mlle. Sokolowa (1890) and Noren (1907) no 
cross walls are formed until tbe tube-like cells meet at tbe center 
of tbe prothalhal cavity. Miss Ferguson (1904), however, finds 
