96 MARGARET C. FERGUSON 



the FucacecB^ and spindles of intranuclear origin have been 

 described by others. But while the achromatic figure in the 

 division of the central cell in Pinus comes to lie completely 

 within the nucleus, I would not claim that it is wholly of nuclear 

 origin ; if such were its source, the cytoplasmic activity in con- 

 nection with this division would be inexplicable. The earliest 

 stages in spindle-formation in this mitosis have not been ob- 

 served as yet, but when the transitional steps between the phases 

 represented in figs. 186 and 187 have been observed we shall 

 doubtless find that the cytoplasm has had some part to play in 

 the institution of the spindle. During the early metaphase of 

 the division the nuclear membrane can still be distinguished, 

 and clearly consists of a weft of threads (figs. 187, 188). I 

 have not observed any phenomenon in the prophase of this 

 mitosis at all comparable with the beautiful figure shown by 

 Murrill ('00), as illustrative of the prophase of the division of 

 the central cell in Tsuga, 



When the spindle arises, it is " multipolar in an axial plane " 

 and thus corresponds, with slight variation, to the mitotic figure 

 described by Duggar ('00) in the microspore of Symj^lo carpus 

 Jxelidus, and by Wiegand ('99) in the microspore of Potamogcton 

 foliosus. In Pinus^ however, the upper extremities of the 

 threads do not at first unite into groups, but remain practically 

 free, and are closely pressed against the neck-cells (fig. 187). 

 The several poles, formed at the inner or lower extremity of the 

 kar3^okinetic figure, soon draw together forming a single, very 

 sharply defined pole ; or the fully developed spindle may remain 

 more or less truncate at its lower end. Blackman describes 

 this spindle as bluntly truncate at both extremities. I have fre- 

 quently observed such a spindle during a late anaphase of the 

 division, but this is only one of the various aspects which may 

 be presented during metakinesis and later stages in this mitosis. 

 The upper extremities of the achromatic spindle-fibers may 

 never draw together at all ; they may unite to form two or more 

 poles ; or they may give rise to one pole which may be blunt 

 or very slender (figs. 190-194). But whatever form may be 

 assumed by this spindle during the later stages in its develop- 

 ment, there is always formed, at an early period, a diarch spindle 



