Marquette, Banifestations of polarity in plant cells whicli usw. 293 
accummulation in tlie intervals between successive divisions if it 
were not for tbe fact that liere and there a cell is found whicli 
is well supplied with starch in the late propliases or anaphases. 
It is possible that such cells possessed a superabundance of starch 
so that although a part was used during mitosis a large amount. 
still remained, but as far as my observations go at present nothing 
can be said about this with certainty. 
It should be mentioned, too, that now and then one or several 
starch grains are found lying outside of the polar structures in 
the cytoplasm. These are isolated cases and seem to liave no par- 
ticular significance. 
The kidney shape assumed by tlie daughter nuclei at the time 
of their formation persists for a considerable period. Frequently 
it is still present wlien the new nuclear membrane has been 
completely formed and the chromatin quite uniformly distributed 
through the nuclear space. As is well known, the nuclei of animal 
cells frequently show during the telophases and even later a marked 
indentation on their polar side; in this indentation or just opposite 
it the central body lies. This relation is duplicated in the cells 
of the young leaves of Isoetes only that in this case the position 
of the central bodies is occupied by the polar starch masses. 
Usually they lie closely pressed to the nucleus completely filling 
its indentation. The cell represented in figure 7 has the upper polar 
structure developed just as well as the-lower only the greater part of 
it lies in the next section. 
Cell division takes place according to the method characteristic 
of the higher plants. A well developed spindle is formed, wliich, 
as it spreads out more and more laterally, is distinctly fibrous only 
at the periphery, its interior already shows the structure whicli 
tlie cytoplasm of the so-called „resting“ cell presents. The polar 
structures whicli tili now had the shape of a more or less flattened 
and irregulär sphere become more elongated and frequently press 
deeply into the nucleus. The nucleus has been increasing in size 
all this time and the indentation in it may be due either to its 
growing up around the polar structure, or to an active pressing 
into it’on the part of the polar structure. With this the cell has 
passed once more into tlie typical resting condition. Before entering 
into a discussion of tjie more general bearings of the observations 
just described upon the problems of nuclear and cell-division it will 
be well to see to what extent structures similar to the polar 
structures of Isoetes occur in other plants. 
As, early as 1839 Von Mo hl 1 ) described for tlie spore-mother- 
cells of Anthoceros a green polored, starch-containing body 
(chromatophore) lying at one side of the nucleus. This chroma- 
tophore divides in tlie middle, and then each half again divides 
so that there are four of them placed about the nucleus at about 
1 ) Von Mohl, H: Über die Entwickelung- der Sporen von Anthoceros 
laevis. (Verm. Schrftn. p. 84.) 
Beihefte Bot. Central!)]. Bd. XXI. Abt. I. Heft 3. 
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