LIFE HISTORY OF PINUS 95 



uncinata the number is larger, averaging about five. As 

 many as nine have been observed in a given prothallium in 

 Pinus montana var. uncinata. The form of the mature egg 

 depends largely upon the number and arrangement of the 

 archegonia. When there are not more than two or three, as is 

 frequently the case in Pinus Strobus, they may become almost 

 spherical in outline. 



Division of the Central Cell. As the central cell prepares 

 for division the cytoplasm between its nucleus and the neck- 

 cells is apparently resolved into fine granules, and there is a 

 more or less pronounced condensation of the cytoplasm about 

 the lower side of the nucleus. At the same time the nucleolus 

 disappears wholly or in part, the nuclear reticulum becomes 

 more open and broken, and the chromatin collects or condenses 

 at various places on the network (fig. 182). Soon a clear 

 court, similar to that described by Hof ('98), Fulmer ('98), 

 Nemec ('98 and '99), Strasburger ('oo) and others, makes its 

 appearance along the lower half of the nucleus. Inasmuch as 

 this nucleus is pressed close against the neck-cells such a court 

 does not arise along its upper side (figs. 183, 184). Delicate, 

 granular threads cross this court and press against the nuclear 

 membrane, while at the same time the upper and lower surfaces 

 of the nucleus become irregularly indented (fig. 185, plate XVII). 

 As the chromatin condenses to form the spireme, an achromatic 

 network, as already described for the corresponding stage in the 

 division of the generative nucleus in Pinus^ becomes apparent 

 in the nuclear cavity (figs. 182-185). When the spireme is 

 fully established it presents a beautiful nioniliform appearance, 

 and the longitudinal splitting of the band becomes apparent at 

 some points. The threads which arose earlier in the cytoplasm 

 seem at this time to have been again resolved into granules (fig. 

 186). Whether any of them enter the nuclear cavity and con- 

 tribute to the formation of the achromatic spindle has not been 

 definitely ascertained. The spindle, when formed, lies wholly 

 within the area previously occupied by the nucleus. Webber 

 ( J oi) finds the origin of the spindle in the division of the gener- 

 ative cell in Zamia to be intranuclear. Farmer and Williams 

 ('96 and '98) ascribe such an origin to the spindles studied in 



