167 
Recent researches upon certain brown algae (Dictyota,* Stypocaulon’ 
and Fucus?) have shown that the centrosome in plants is in all probability 
something more than a mere point of insertion of the kinoplasmic radia- 
tions. In Dictyota there seems to be no doubt but the centrosome is a 
definite body, being here relatively large and rod-shaped, and from which 
kinoplasmic fibres radiate. In the vegetative cells of Marchantia I can 
not assert with absolute certainty that a definite central body or centro- 
some exists in all cases, but I believe that such is the case. In some in 
Which the kinoplasmic radiations are densely stained, the dark center 
seems to be merely the point of union of the radiations, but if the stain 
be washed out so that the radiations are almost colorless, a well-defined 
and densely-stained central body is generally to be seen. Since it is now 
known that the small hyaline space in which the centrosome is some- 
times seen to lie, is an artefact, the term centrosphere at present has 
reference to the centrosome with its radiations, and it is in this sense that 
the word is here used. By the time the chromosomes are differentiated, 
and even earlier, the centrospheres lie nearly diametrically opposite each 
other, and appear to be in all cases attached to the nuclear membrane. 
The nucleus is now generally elliptical in shape with rather pointed ends 
at which the centrosomes are situated. As Farmer states, it does seem 
that the centrospheres exert a pulling strain upon the nucleus, and I have 
often found that the ends were prolonged into slender beaks terminating 
in the centrospheres. 
I have not as yet been able to obtain a series of stages illustrating the 
formation of the spindle. The mature spindle consists of delicate bundles 
or strands of kinoplasmic fibres extending from pole to pole. The fibres 
stain readily with gentian violet, so that the spindle although often quite 
small is not an inconspicuous object even when observed by means of dry 
lenses. 
As soon as the chromosomes are regularly arranged in the equatorial 
plate, the polar radiations become faint and soon disappear. In some 
eases no polar radiations were visible at this stage. 
1 Mottier, D.M.: ‘Das Centrosom bei Dictyota (Vorliiufige Mittheilung).’’ Ber. der 
deutsch. bot. Gesellsch., XVI, 1898. 
2 Swingle, W. T.: ‘‘ Zur Kenntniss der Kern- und Zelltheilung bei den Sphacelari- 
aceen,”’ Jahrb. fiir wiss. Bot., XXX, 1897. 
° Strasburger, E.; ‘‘ Kerntheilung und Befruchtung bei Fucus,’’ Jahrb. fiir wiss. Bot 
XXX, 1897. 
