Nichols, A morphological study of Juniperus communis var. depressa. 225 
Division of the central cell nucleus. — About tbree 
days before fertilization the nucleus of the central cell divides, 
giving rise to the ventral canal nucleus and the egg nucleus. 
Strasburger (1879) figures the spindle of this division in J. vir- 
giniana, and it has recently been described in J. communis by 
Noren (1904, 1907) and Sludsky (1905). Up to this time the 
central cell nucleus has exhibited no unusual structural peculiarities 
It possesses a delicate reticulum in which dark staining masses 
and irregulär, light staining threads are discernible and has awell 
defined nucleolus (fig. 79). As the nucleus approaches division 
more or less continuous, comparatively thick threads arise in which 
a distinction between chromatin granules and linin is apparent 
(figs. 80, 81), and at the same time the nucleolus tends to stain 
less deeply and reveals a vacuolate structure (fig. 93). 
Coincident with these changes within the nucleus the nuclear 
membrane on the surface toward the asteroid becomes pressed or 
drawn inward in the manner shown by figs. 80 and 81, while 
delicate granulär radiations extend between the center of the 
asteroid and the invagination thus formed. The first impression is 
that these radiations represent fibers pressing into the nuclear 
cavity, but the careful examination of a large number of pre- 
parations has failed to reveal any actual connection between them 
and the spindle fibers eventually formed. Similar phenomena 
have been variously interpreted by different writers. Mur rill 
(1900) finds that in Tsnga the spindle fibers, arising within a fibrous 
mass beneath the nucleus “grow upward against and press in the 
nuclear membrane”, and that the membrane then “disappears below, 
and the spindle fibers press into the nuclear cavity”. Miyake 
(1903 a) reports that in Picea “the spindle fibers first arise from a 
clear court along the lower side of the nucleus and grow into the 
nuclear cavity”, pressing in the nuclear membrane in the manner 
described by Murrill. Miss Ferguson (1901) also describes a 
clear region with delicate granulär threads along the lower half of 
the nucleus in Pinus, and an irregulär indentation of the upper 
and lower surfaces of the nucleus. but she fails to ascertain whether 
any of the threads enter the nuclear cavity and contribute to the 
formation of the spindle, while Coker (1903b) concludes that in 
Taxodium the spindle fibers are almost entirely of nuclear origin. 
Of c-ourse, if such is the case, as Miss Ferguson remarks, “the 
cytoplasmic activity in connection with this division would be in- 
explicable”. Xevertheless, in the light of the writer’s observations, 
the asteroid does not appear to contribute to the formation of the 
spindle, and its only apparent use in Juniperus is to form a Support 
for the free lower pole of the spindle, a function already suggested 
by Mu-rrill (1900). 
The 'division of the central cell nucleus is consummated 
rapidly and takes place almost simultaneously in all the archegonia 
of a group. In one ovule, for example, eight such nuclei were found 
undergoing division. With the formation of a continuous spirem 
the distinction between chromatin and linin disappears, and the 
Beihefte Bot. Centralbl. Bd. XXV. Abt. I. Heft 2. 15 
