Marquette. Manifestations <>l' polarity in planl cells which usw. 291 



represents a provision for the anchoring of the spindle. If such 

 is the case, it is not impossible that the polar stmetures of Isoetes 

 exercise a similar function in the later stages of nuclear division. 

 But it is to be noted that the cells here for the niost part are not 

 especially long in proportion to the size of tlie spindle, so that in 

 niost cases the spindles might easily reach froni one wall to the 

 other. 



The passage of the chromosomes from the equatorial plate to 

 the poles seems to progress more slowly in the young leaf-cells of 

 hoetes than it does in many other cases so that a large number 

 of intermediate stages between early and late anaphases are met with. 



The spindle-poles persist tili a late stage so that when the 

 chromosomes are closery packed together in the diaster, and it 

 seems as if the new daughter nuclear membrane were about to 

 appear, the two spindle poles are still sharply defined. They are 

 no longer composed of fine clean-cut fibers, but show a finely granulär 

 structure, and appear almost homogeneous. They also have changed 

 in their staining qualities. At the equatorial plate stage the spindle 

 stains blue (with the triple stain) now, howewer, its remaining ends 

 take a yellow to a reddish color. The shape of the spindle ends 

 has also changed as a comparison of figs. 5 and 6 shows. 



Sharply defined spindle-poles in the later stages of nuclear 

 division are not common in plant cells. Rosen 1 ) figures one case 

 for Psilotum and Osterhout 2 ) does the same for Equlsetam; in 

 Fuligo z ) they seem to be of regulär occurrence. Also in the 

 pollen-mother cells of Nymphaea, the spindle-poles remain intact 

 for a longer timc 4 ) but instead of their sides including a wider 

 and wider angle as division progresses as in the case in Isoeies 

 the remaining spindle ends become thinner and thinner. In animal 

 cells it is not so rare to find the spindle ends persisting through 

 the later anaphases. 



As at the time of the equatorial plate stage, the spindle-poles 

 continue cluring the anaphases to press into the polar structures. 

 These have changed little, possibly they have become slightly 

 flattened in the direction perpendicular to the spindle axis. 

 Occasionally a starch grain lies exactly at one or at both of the 

 sharply pointed spindle-poles, this, however, to all appearances is 

 not at all a constant occurrence. As the chromosomes go back to 

 the poles well developed connecting fibers appear between the 

 chromosome groups. later they are seen to extend also to the sides 

 of the chromosomes, ending at the polar structures. They are 

 delicate, sharply defined fibers which stain blue in the triple stain. 

 In the equatorial region they are crowded together in groups and 

 more or less wound about each other while nearer the chromosomes 



a ) Beiträge zur Kenntnis der Pflanzenzellen. (Colin : s Beitr. z. Biol. <l. 

 Pflanzen. Bd. VII. Taf. IV fig. 4.) 



2 ) Jahrb. wiss. Bot. Bd. XXX, Taf. II, Fig. 18. 



3 ) Harper, R. A.: Gell and nuclear division in Fulioo varians. (Bot. Gaz. 

 Vol. XXX. 1900. p 217.) 



4 j See Strasburger: Hist. Beitr. VI. PI. IV, figs. 170 and 171. 



