Pollen Mother-cells of Lilium canadense. 2 1 3 
short, thick bodies, so closely appressed to one another that the double 
nature of the whole is often quite difficult of detection. In the best iron 
haematoxylin preparations, however, the daughter segments can always 
be distinguished. In no case have I found any evidence of a splitting 
of the daughter chromosomes at this stage, such as Strasburger (’00) 
describes in Lilium Martagon. Figs. 57 and 59 show their appearance 
in polar view ; Figs. 56 and 60-67 represent them as seen when the line 
of vision is practically in the equatorial plane. The chromosomes com- 
monly retain something of their original twist (Figs. 59, 60, 63-67, and 
most of those shown in Fig. 57) ; they are gradually untwisted by the 
separation of the daughter chromosomes. Others appear simply as pairs of 
straight or curved rods in contact at their middle portion or throughout 
their length (a, Fig. 57, Fig. 61). I have found none which were in 
contact at the ends and divergent in the middle, excepting in such cases 
as Fig. 67, in which the opening in the middle is plainly due to the 
beginning of the separation of the daughter chromosomes. Rarely the 
daughter chromosomes appear to be completely fused at one end 
(Fig. 62). 
Fig. 57 shows the arrangement of the chromosomes in the equatorial 
plate as seen in polar view. I have found no variations from the typical 
number (twelve) in any case in which the section was thick enough to 
exclude the possibility of one or more being missing. The majority of the 
chromosomes are arranged about the periphery of the plate, with a few, 
commonly two or three, lying at various angles in the central region. Of 
those which lie in the periphery, the usual orientation is radial, as the 
figure shows ; but it is not uncommon to find a peripheral chromosome 
which lies tangentially to the spindle. 
Each radially arranged peripheral chromosome (Fig. 56) has a bundle 
of spindle fibres attached to the inner end of each daughter segment, the 
outer end then extending out perpendicularly from the spindle into the 
cytoplasm. To this statement as to the attachment of the fibres to the 
radial chromosomes I have found no exception. In viewing the spindle 
from the side (as in Fig. 56), these radially arranged chromosomes present 
quite different views, according as they lie in the central portion of the 
figure, and are then seen from the end. or as they lie at the sides, and are 
seen laterally. In the former case, the ends of the two daughter chromo- 
somes turned toward the observer are usually seen to be in close contact 
and often flattened against each other. These two ends may lie side by 
side in the equatorial plane (Fig. 56, second from right), or in a plane 
parallel with the spindle axis (Fig. 64), or in any intermediate position. 
This variation in the relative position of the outer ends is accounted for 
by the different degrees to which the daughter chromosomes are twisted 
about each other, and by the varying amounts of untwisting which they 
