Marquette, Manifestation of polarity in plant cells which usw. 299 
free from starch. They may therefore for tlie present be de- 
signated simply as polar strnctures. 
It is perhäps conceivable tliat these „structures“ are nothing 
niore tlian a mass of starcli grains and dissolved starch trans- 
formation-products which withont further changes are not easily 
miscible witli the surrounding cytoplasm and hence is separated 
from it by a surface tension film. i. e. forms a vacuole. To be 
sure the shape of these strnctures is not tliat of an ordinary 
vacuole. This is especially true during the prophases when the 
polar strnctures are markedly üattened and irregulär in outline. 
However, if solution processes take place with varying intensity 
at various parts of tlie surface of a vacuole the differences in 
surface tension brought about by this might result in corresponding 
changes in form of the vacuole. It is possible further that af'ter 
tlie last starch grains had disappeared tlieir immediate trans- 
formation products would still be present and accordingly the 
vacuole which owed its formation to the presence of starch grains 
could persist even after the last starch grain as such had dis¬ 
appeared. This hypothesis is, however, highly improbable for the 
polar strnctures of Isoetes also occur in tissues which to all 
appearances have for long periods contained no starch wliatever 
as for example the vegetative points of young root-tips. Here the 
cells are entirely free from starch and apparently have not contained 
any for at least a large number of.cell generations; nevertheless 
all the cells here possess these polar strnctures. 
If an explanation of tlie bodies in question involved merely 
the matter of accounting for the accumulation of a number of free 
starch grains at the spindle-poles one might follow the lines of 
the kinoplasmic theory and conceive the visible changes taking 
place in the cell during division as the expression of the coordinated 
activities of a System of kinoplasmic übers. It is further assumed 
that in addifion to these more active constituents of the cell other 
parts are more passive, the so-called „metaplasni", aggregations of 
food material,*etc. If these are freely movable the may tend to 
collect at the points of equilibrium, or regions of greater quietude, 
in the active System, just as for example the sand grains aggregate 
at the points of rest in a vibrating plate in the production of the 
familiär Hhladni ügures. If we assume that the spindle poles in a 
dividing cell are regions of relative quiet, then the accumulation 
of passive bodies aboiit 1 tliose points follows as a matter of course. 
There are numerous Statements scattered through tlie literature 
reporting the aggregation of more or less passive bodies in the 
neighborhood of tlie spindle poles. Karsten 1 ) for example found 
that in diatoms the chloroplasts tend to collect about the spindle 
poles; Van Hook 2 ) made similar observations for Marchantia. The 
q Karsten: Die sogenannten „Mikrosporen“ der Planktondiatomeen und 
ihrer weiteren Entwickelung, beobachtet an Corethron Valdiviae. n. sp. (Ber, 
d. deut. bot. Ges. Bd. XXII 1904. p. 544. See figs. 2 and 2a PI. XXIII.) 
2 ) Bot. Gaz. Vol. XXX. PL XXIII. Eig. 2. 
