290 3Iarquette. Manifestations of polarity in plant cells whtcli usw. 



results, the ends being drawn out as it were to needle points. 

 The polar starch-bodies round up niore and more so that by the 

 tiuie the chromosonies are arranged on the equatorial plate they 

 have once niore a more or less irregulär spherical shape. The sharp 

 spindle poles press into these irregularly spherical polar structures 

 producing an appearance not unlike that obtained when a pointed 

 body presses into a mass of stuf dough. (Fig. 5.) We are here 

 dealing with an actual indentation of the surface of the rounded 

 polar structure and not with an appearance such as is sornetimes 

 niet with in the astrospheres of animal cells. Here namely, if the 

 spindle-ends extend into the astrosphere a part of the sphere is 

 replaced by them though a superficial Observation niight give the 

 impression that here too the spindle indents the sphere. This is 

 especially true of those cases in which there are difierences in the 

 Stauung reactions of sphere-rays and spindle fibers, or where the 

 spindle fibers are closely packed and distinctly fibrous while the 

 sphere has more of a granulär appearance. It requires but a giance, 

 however. to show that in these cases the appearance is due to 

 the absence of a sector of the astral rays and their replacement 

 by the spindle fibers. and not to an indentation of the surface of 

 the sphere. 



The completed spindle of the young leaf-cells of Isoeies is made 

 up of numerous fibers. They are delicate. unusually clean cut, and 

 closely packed: the result is a spindle of sharp outline which Stands 

 out iu jstrong contrast to the pale cytoplasm surrounding it. In 

 fact, the surrounding cytoplasam at this stage seems to consist of 

 little but watery cell-sap; the Strands or lamellae of its more solid 

 constituents are delicate and widely separated. The relation between 

 the spindle and the surrounding cytoplasm is only imperfectly 

 represented in Fig. 5, the spindle should be considerably darker in 

 comparison to the surrounding cytoplasm. It is to be noted that 

 there is a definitely fixed relation between the position of the polar 

 structures and the axis of the spindle. TTithout exception the 

 spindle lies so that its ends press into approximately the middle 

 of the polar structures. This invariable relation Stands out with 

 especial clearness when. as is not seldom the case, the polar 

 structures lie at diagonally opposite corners of the cell. In these 

 cases the spindle also lies diagonally so that here as always its 

 ends indent the approximate centers of the polar structures. 

 Occasionally it happens that the spindle figure lies far over at one 

 side of an unusually broad cell with the spindle axis parallel to 

 the side of the cell, and in these cases the polar structures also 

 show the same degree of displacement towards the side of the 

 cell. In this connection Strasburger's conception 1 ) of the anchoring 

 of the spindle figure in those cases in which its poles do not reach 

 to the plasma membrane comes to mind. He assumes that the 

 dense trophoplasmic layer which frequently surrounds the spindle 

 figure in these cases and into which the spindle-poles extend 



*) Hist, Beitr. VI p. 152. 



