Marquette, Manifestation of polarity in plant c-ells which usw. 989 
closer together. These conditions are still more clearly sliown in 
cells in which a more considerable space remains between the 
polar structures and the plasma membrane as frequently happens 
in cells which are elongated more tlian usnal. In these cases the 
cytoplasm next to the outer boundary of the polar structures 
appears as a dense almost finely granulär mass, further outwards 
towards the plasma membrane its structure becomes looser. Not 
rarely this denser part of the cytoplasm is fairly sharply bounded, 
resting 011 the polar structure like a more or less crescent 
sliaped mass. The Strands or lamellae of the less dense adjacent 
cytoplasm extend out from this denser mass to the cell periphery 
in a more or less radial arrangement. The appearances just 
described are especially well brouglit out in preparations stained 
in iron-haematoxylin. The dense cytoplasmic mass stains more 
intensely than the surrounding cytoplasm and strongly suggests 
on archoplasmic region such as has beeil figured for various 
animal cells. 1 ) 
When the polar structures have reached their definitive posi- 
tions or even as they were moving away from the nucleus, the 
spindle übers begin to appear, and it is to be observed tliat withont 
exception they extend between the polar structures and the adjacent 
surface of the nucleus. In tlie earlier stages of spindle formation 
the übers present the appearance of a tangled network. TThether 
the übers actnally brauch and anastomose or wlietlier the appear¬ 
ance is 111 erelv due to an intertwining of sinuons but unbranched 
übers mäy be left undecided for the present. White the spindle- 
fibers are developing the nucleus changes its shape. It expands 
laterally and at the same time short ens in the direction of its form er 
long axis so that finally its long axis is perpendicular to tliat of 
the cell. The nucleus no longer has the smootli. regulär, ellipsoidal 
outline it possessed in the earlier stages but shows a shallow inden- 
tation at the places where the spindle übers come in contact with 
it. The appearance strongly suggests a pressing in of the nuclear 
membrane on the part of the spindle übers. Whether such is 
actually the case I have not determined. 
Simultaneously with these changes in the shape of the nucleus 
its membrane begins to disappear. The stages in the disappearance 
of the membrane are not easilv followed since the nuclear membrane 
kJ 
is never verv conspicuous in these cells. However, to all appearances 
it seems evident that the membrane first disappears at the points 
where the spindle übers come in contact with it. (Fig. 4) The 
chromosomes at this time lie, more or less wound about each other, 
fairly uniformly distributed through the nuclear space. 
The spindle übers begin to stand out more sharply now. assume 
a straighter course. and approach each other more closely at tlieir 
distal ends until finally an exceedinglv sharp pointed spindle 
1 ) Hermann, E.: Beiträge zur Lehre von der Entstehung der karyo- 
kinetischen Spindel. (Arch. f. mifir. Anat. Bd. XXXVII p. 569. See figs. 53.5. 
etc. PI. XXXI.) 
