Marquette, Manifestations of polaritj in plant cells which usw. 299 



free frouj starch. They may therefore for tue presenl be de- 

 signated simply as polar structures. 



It is perhaps conceivable that these „structures" are nothing 

 more than a mass of starch grains and dissolved starch trans- 

 formation-products wliich without further changes are not easily 

 miscible with 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 structures is not that of an ordinary 

 vacuole. This is especially true during the prophases wheu the 

 polar structures are markedly flattened and irregulär in outline. 

 However, if Solution processes take place with varying intensity 

 at various parts of the 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 after 

 the last starch grains hacl disappeared their 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 structures of Isoetes also occur in tissues which to all 

 appearances have for long periods contained no starch whatever 

 as for example the vegetative points of young root-tips. Here the 

 cells are entirely free from starch and apparently have not contained 

 airy for at least a large number of cell generations; nevertheless 

 all the cells here possess these polar structures. 



If an explanation of the 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 fibers. It is further assumed 

 that in addition to these more active constituents of the cell other 

 parts are more passive, the so-called „metaplasm", 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 Chladni figures. If we assume that the spindle poles in a 

 dividing cell are regions of relative quiet, then the accumulation 

 of passive bodies about those points follows as a matter of course. 

 There are numerous Statements scattered through the literature 

 reporting the aggregation of more or less passive bodies in the 

 neighborhood of the spindle poles. Karsten 1 ) for example found 

 that in diatoms the ehloroplasts tend to collect about the spindle 

 poles; Van Hook' 2 ) made similar observations for Marchantia. The 



x ) Karsten: Die sogenannten „Mikrospuren" der Planktondiatomeeu 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. PI. XXIII. Fig. 2. 



