1909] GATES—CHROMOSOMES IN OENOTHERA 183 
referred to these appearances in an earlier paper (9,‘p. 19). In jig. 2 
the chromosomes are more irregular in shape, and their bivalent 
character is not so evident. There are 11 chromosomes in the 
daughter group, and examination of the adjacent sections showed that 
there were g and no more at the other end of the spindle. The 
globular black bodies seen in the figure are frequently found scattured 
near the periphery of the cytoplasm. They stain like chromatin 
with Haidenhain’s iron alum hematoxylin, but their chemical 
nature is unknown. Figs. 3-5 each show 10 chromosomes. Fig. 6 
is a telophase with 11 chromosomes, the next section showing 9 at 
the other end of the spindle. Fig. 7 is an exact polar view, the 
other figures being more or less oblique cuts of the spindle, but the 
spindle fibers are not represented. Figs. 7, 8 are somewhat later 
stages in side view, soon after the nuclear membrane is formed. Ten 
chromosomes are present in each. In figs. 9, ro are shown in outline 
the loop-shaped chromosomes of two somatic cells. Each has 20 
chromosomes. ‘The cells are from the middle layers of the anther 
wall. 
Plates XIII and XIV deal with plants having 21 chromosomes. 
Fig. 11 is a side view of the heterotypic spindle, showing 20 or 21 
chromosomes. It is usually difficult to count the chromosomes 
_ exactly at this time in a side view of the spindle, on account of the 
close aggregation of some of them, and the presence of spindle fibers. 
he chromosomes are almost never regularly oriented in an equatorial 
plate on the heterotypic spindle. An examination of the literature 
shows that in most plants and animalsa flat equatorial plate is formed 
in the metaphase of this mitosis as in other mitoses, although a few 
forms constitute exceptions. But the homotypic mitosis in Oenothera 
has always a very definite equatorial plate, in which the chromosomes 
are oriented in a single plane. There can be little doubt that the 
irregularities in chromosome distribution arise from this failure of 
the chromosomes to be regularly paired and oriented on the heterotypic 
spindle. The irregularities in distribution certainly arise at this time. 
I have recently confirmed practically all the events of reduction 
by a study of the wild O. biennis, so that this account of reduction 
applies to the genus Oenothera in general and is not the result of 
mutative conditions. This will be referred to again later. 
