Marquette, Manifestations of polarity in plant cells which usw. 285 
4 
held quite generally amongst botanists tliat in tlie yascular crypto- 
gams and in tlie Phanerogams tlie karyokinetic spindle develops 
without tlie participation of a centrosome. 
It sho.uld be mentioned tliat Guignard, 1 ) who more than anyone 
eise lias busied liimself witb tlie question of tlie existence of centro- 
somes in tbe higher plants, lias sought to bring bis earlier Statements 
into barmony witb tbe discovery of tbe multipolar stage in spindle- 
development by tbe assumption of multiple centers. In so doing, 
bowever, be dispensed witb one of tbe most important cbaracter- 
istics of tlie centrosomes as tliey are known in tbe animal cells: 
tliat is, tlieir constant bipartition and tbe innnediate establisbment 
of a bipolarity of tbe cell as soon as tbe daughter centers separate. 
According to tbe present most fully developed conception 
concerning tbe processes of division in tbe liigber plants, tliat is, 
according to the „kinoplasm“ theory as advanced by Strasburger 
and bis pupils, we have in tbe cytoplasmic fibers or rays units 
wliicli in coordination witb one anotber go tbrough tbe various 
movements and transpositions necessary to produce tbe bipolar 
spindle. At no time during tbe wbole process do structures appear 
wbicli could be compared witb centrosomes. Not only is nothing' 
to be seen of a central body, but tbe assumption of its invisible 
presence is entirely superfluous. Tbe fibers considered as co-ordi- 
nated units give just as satisfactory an account of tbe processes 
observed in spindle formation as can be given by assuming tbe 
presence of a minute granule wbicli in some mysterious manner 
Controls tbe activities of tbe fibers. 
Tbe question still remains as to liow on tbe kinoplasm liypo- 
tbesis tbe fibers so coordinate tlieir activities as to constantly 
produce a bipolar Organisation and consequent bipartition of tbe 
mother cell, and furtber, as to liow tbe process of division witb 
tbe presence of a central body, wliatever its function, as found in 
tbe algae and fungi bas passed over into tbe type of division 
without a central body as found in tbe liigber plants. Froni this 
standpoint I have undertaken tbe studies on nuclear and cell 
division in Isoetes described below. 
Leare a wider space between tbese two paragrapbs. Tbe material 
for tbis work was collected at Devils Lake, Wisconsin, wkere 
Isoetes laciistris grows abundantly, putting forth new leaves from 
tbe beginning of spriilg tili late in tbe fall. Of tbe various fixing 
fluids in common use, Flemming’s stronger cbrom-osmium-acetic 
mixture gave tlie best results. Tbe material was imbedded and 
sectioned in tbe usual way. Tbe sections were stained for tbe 
great er part either witb Flemming’s triple stain or witb Heiden- 
liain's iron baematoxylin. 
Leaves which have reached a lengtb of about 5 nun show a 
large hinüber of nuclear and cell divisions and eveu a hasty survey 
J ) Guignard, L.: Les cqntrosomes chez les vegetaux. (Compt. Bend, 
TCXXAh 1897. p. 1148.) Les centres cinetiques cliez les vegetaux. (Ann. d. Sei. 
Nat. Bot. 8e Ser. TVI. 1897. p. 177.) 
