118 A CYTOLOGICAL INVESTIGATION OF SOME SPECIES 
Of these, alcohol acetic- acid gave the best results. JuEL’s fluid and 
the alcohol-chloroform-acetic acid mixture made the plasma De so 
‘considerably that these fluids were useless. 
The Flemming-material also was less well fixed than the alcohol- 
acetic material while the staining by means of haematoxyline was bet- 
ter in the latter case also, so that finally this fixing fluid was selected 
and all the material investigated thus fixed. Some kinds gave always 
good fixations, while others always gave less good ones. The fixation of 
the nuclei however was always satisfactory. 
As it was undesirable to cut whole spikelets in the microtome becau- 
se the outer glumes are rather hard and possess, so as the top of the 
third glume, many hairs containung silica, the spikelets were deprived of 
their glumes,while in a dish with alcohol, under a binocular microscope. 
During this manipulation flowers for further investigation, probably 
containing pollen-mothercells in the desired division-stages, were selec- 
ted. This can be done by taking anthers from the sessile or pedicelled 
spikelets situated close below the top and others from the base of the 
flowering anthers and by examining these subsequently in a drop of 
water under the microscope. This is feasible because in the fixed ma- 
terial also, through the wall of the anthers, the pollenmothercells and 
pollengrains can clearly be seen. A little pressureon the coverglassoften 
suffises to expel part of the pollen-mothercells from the anthers in 
which case the chromosomes can be distinguished, as bodies strongly 
refracting the light, in the as yet unstained cells: even diakinesis-stages 
and metaphases can then clearly be seen. If the spikelets close to the 
top of a flowering axis contain pollen-mothercells or tetrads, while 
those at the base of the axis contain pollen-mothercells, in which chro- 
mosomes are as yetundistinguishable, it is almost certain, that the de- 
sired stages occur in the spikelets between the two, so that in choosing 
these for further investigation, series of flowers are obtained in which 
all stages of karyokinesis occur from synapsis or spirems to homotypi- 
cal divisions inclusive. A great disadvantage of Flemming-fixed mate- 
rial, is the impossibility to determine the kind of division stages pre- 
sent in the flowers on account of the blackening of all tissues, so that 
many flowers are put aside for further investigation which are useless 
for our purpose. 
The flowers, selected in the way just described, were carried into 
