Marquette, Manifestations of polarity in plant cells which usw. 287 



lias its explanantiou partly in the fact that differenl leaves vary 

 in tlie amount of starch they carry, and Hurthermore, that the 

 starch is not uniformly distributed throughout a whole leaf. Nol 

 rarely there are cells which contain no starch at all, but in 

 them this peculiär body is none the less present. It is merely 

 not so cönspicuous as when it contains deeply staining starch 

 grains. While these variations in the starch content of different 

 leaves make difficult a final judgment as to whether the amount 

 of starch in any particular cell varies with its condition of devel- 

 opment, it seems none the less as if the starch content of the 

 individual cells undergoes periodical changes parallel with the 

 karyokinetic cycle. 



More important than the variations in the amount of starch 

 contained in these structures are the changes in shape and in 

 Position which they undergo and which upon closer examination 

 are seen to be in intimate relation with the processes of nuclear 

 division. As was stated above, there are invariablv either one 

 or two of these structures in a cell, and examination sliows that 

 whether one or two are present depends upon the condition of the 

 cell with respect to division. 



Immediately after cell division, each daughter cell invariablv 

 contains a Single starch mass, and this condition continues also in 

 the completely reconstructed and so-called „resting" cell. In such 

 cells the starch-body lies close to one side of the nucleus, in most 

 cases presses into it so that the nucleus is deeply indented. (Fig. 1.) 

 The shape of the starch body varies considerably. Frequently it 

 is fairly well rounded, but at other times is more elongated as in 

 Fig. 1, here it is seen extending out from the polar depression in 

 the nucleus, bending to one side and running along closely pressed 

 to the nucleus for some distance. By focusing deeper down into 

 the section it can be seen that the starch body also extends 

 beyond the polar depression of the nucleus on its under side, 

 spreading out somewhat into the cytoplasm. In this figure, as 

 always, the polar indentation in the nucleus is on the side opposite 

 the newly formed cell wall. 



In the young leaves of Isoetes cell divisions follow rapidly 

 one upon the other so that there is some difficulty in deciding 

 whether a cell is in a perfectly „resting" condition or whether the 

 prophases of the next division are already in progress. The 

 most characteristic indication of an approaching cell division is 

 that the Single starch body of the „resting" cell divides into two. 

 Stages showing the division of this body are sharply marked and 

 not difficult to find. The body elongates and at the same time it 

 constricts in its middle portion until finally it separates into two. 

 While this is going on the starch body maintains its close contact 

 with the nucleus. In fact it is so pressed into the nucleus that 

 a furrow is formed in the surface of the latter through which the 

 separating halves of the starch body draw apart, at the same time 

 the nucleus is also elongated in the direction of the Separation of 

 the daughter starch bodies. (Fig. 2.) The chromatin at tliis staut- 



