281 
Manifestation^ of polarity in plant cells which 
apparently are without centrosomes. 
By 
W. Marquette. 
With plate XIII. 
The existiug evidence seems to favor the yiew that the for- 
mation of the karyokinetic spindle occurs in quite a different 
iasliion in the animals than in the higher plants. The most fre- 
qnently noted and discussed difference in the two cases is the 
presence of the so-called centrosome in the one and its at least 
apparent absence in the other. TThile the existence of the centro¬ 
some as a permanent cell organ in the animal cell is by no means 
universally admitted, the evidence for its occnrrence as such in 
some cases at least seems unqnestionable. The presence of the 
center, as Kabl and Flemming most clearly pointed out, involves 
a visible polar Organization in the cell; even in the resting stages 
the cell shows a polar Organization whose main axis is a straight 
line passing throngh the center and the nnclens. When the cell 
prepares to divide, the centrosome divides first, the two halves 
separate, and the spindle figure develops abont them as centers; 
from the beginning it is a bipolar figure. At any moment then 
such cells present a polar, never an isotropic strnctnre. The most 
tlioroughly studied animal cells in general show such an Organi¬ 
zation as do also many of tlie lower plants. Amongst the Algae 
for example Fucus 1 ) and IHctyota 2 ) show at least dnring the pro- 
cesses of division distinct central bodies, and in the apical cells 
of Stypocaulon 3 ) centre is also present in the resting stages. 
1) Strasburger, E.: Kernteilung und Befruchtung bei Fucus. (Jahrb. 
f. wiss. Bot. Bd. XXX. 1897. p. 351.) 
2 ) Mottier, D. M.: Das Centrosom bei Dictyotci. (Ber. d. Deut. bot. 
Gesel. Bd. XVI. 1898. p. 123.) Xutlear and cell division in Dictyotci dichotoma. 
(Ann. Bot. Vol. XIV. 1900. p. 163.) 
3 ) Swingle, W. T.: Zur Kenntnis der Kern- und Zellteilung bei den 
Spliacelariaceen. (Jahrb. f. wiss. Bot. Bd. XXX. 1897. p. 297.) 
