(ENOTHEKA AUJT. J.ATA AND (E. MUT. SEMILATA. 
541 
and two nucleoli are also present. Fig. 19 shows the hetero- 
typic spindle in a pollen mother-cell in metaphase, all the 15 
chromosomes being represented. In this cell the cytoplasm 
is vacuolate and the chromosomes small, so that the cell is pro- 
bably begiuning to degenerate. In figs. 20, 21 are shown polar 
views of two mother-cells in the same stage. Each contains 
15 chromosomes, but they are much smaller than the normal 
size, and the cells show signs of approaching degeneration. 
From these and following figures it will be seen that the 
chromosomes in lata rubricalyx vary enormously in size in 
different cells, though relatively uniform in size in the same 
cell, the variation in size depending- apparently upon the con- 
ditions of nutrition and prospects for development of the cell. 
Fig. 22 shows a portion of a normal mother-cell of this plant. 
This is a late anaphase of the heterotypic division and the 
spindle has been .cut, so that only 11 chromosomes can be 
seen. But these are full size, and each shows the fission 
which occurs usually as the chromosomes are passing towards 
the poles of the spindle. The chromosome-halves thus formed 
remain paired in this way during interkinesis and then finally 
pass to opposite poles of the homotypic spindle. Fig. 23 
shows one of the two daughter-nuclei of a pollen mother-cell 
in the interkinesis stage after the heterotypic mitosis. In 
this particular case the nucleus contains 7 chromosomes all 
showing their bivalent character, and a small nucleolus. In 
addition, an eighth chromosome has been left just outside the 
nucleus. This is the extra, or fifteenth chromosome which has 
just failed to reach the daughter-nucleus, as not infrequently 
happens. It will later degenerate, and such a mother-cell 
would therefore produce four pollen grains, each containing 
7 chromosomes. 
Figs. 24 and 25 are polar views of the homotypic metaphase 
in lata rubricalyx. In fig. 24 each group contains 7 
whole chromosomes which are more or less clearly split, and a 
half-chromosome. These two halves, which lie facing each 
other, are obviously derived from the fission of the extra 
chromosome in the heterotypic metaphase. They are about 
