Marquette, Manifestations of polarity in plant cells which usw. 291 
represents a Provision for the an clioring of the spindle. If such 
is the case, it is not impossible that the polar structures 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 most part are not 
especially long in proportion to the size of the spindle, so that in 
most cases the spindles might easily reach front one wall to the 
other. 
The passage of the chromosomes front the equatorial plate to 
the poles seents to progress ntore slowly in the young leaf-cells of 
Isoetes than it does in many other cases so that a large nuntber 
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 closely packed togetlier in the diaster, and it 
seems as if the new daughter ltnclear membrane were about to 
appear, the two spindle poles are still sharply defined. They are 
no longer composed of fine clean-cut übers, but show a finely granulär 
structure, and appear alniost homogeneous. They also ltave changed 
in their staining qualities. At’ the equatorial plate stage the spindle 
stains blue (with the triple stain) now, howewer, its rentaining 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 contmon in plant cells. Rosen 1 ) figures one case 
for Psilotum and Osterhout' 2 3 4 ) does the saute for Equisetum; in 
FuUgo s ) they seent to be of regulär occurrence. Also in the 
pollen-mother cells of Nymphaea, the spindle-poles remain intact 
for a longer time 1 ) but instead of their sides including a wider 
and wider angle as division progresses as in the case in Isoetes 
the remaining spindle ends become thinner and thinner. In animal 
cells it is not so rare to find the spindle ends persisting througli 
the later anaphases. 
As at the time of the equatorial plate stage, the spindle-poles 
continue during the anaphases to press into the polar structures. 
These have changed litt-le, 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, liowever, to all appearances is 
not at all a constant occurrence. As the chromosomes go back to 
the poles well developed connecting übers appear between the 
chromosome groups. later they are seen to extern! also to the sides 
of the chromosomes, ending at the polar structures. They are 
delicate, sharply deüned übers which stain blue in the triple stain. 
In the equatorial region they are crowded togetlier in groups and 
more or tess wound about'eacli other while nearer the chromosomes 
J ) Beiträge zur Kenntnis der Pflanzenzellen. (Colin’s Beitr. z. Biol. d. 
Pflanzen. Bd. VII. Taf. IV fig. 4.) 
2 ) Jahrb. wiss. Bot. Bd. XXX, Taf. II, Fig. 18. 
3 ) Harper, B. A.: Cell and nuclear division in Fuligo varians. (Bot. Gaz. 
Vol. XXX. 1900. p 217.) 
4 ) See Strasburger: Hist. JBeitr. VI. PL IV, figs. 170 and 171. 
