94 BOTANICAL GAZETTE [FEBRUARY 
in the last stage of their disappearance they retain their shape but 
lose their staining power, as if the deeply staining substance; (chrom- 
atin?) had been dissolved away, leaving the yellow-staining ground- 
substance, and in the first stage of their reappearance the yellow-stain- 
-ing material only is present. I think this precludes the possibility of 
dentifying the bodies in the cytoplasm, which stain like chromatin, as 
fragments of the nucleolus. 
THE HETEROTYPIC MITOSIS 
Thus far the description of events in the pollen mother cell has 
related only to O. Jata, because the corresponding stages in the O. Lam- 
arckiana side of the hybrid have not been studied. ‘There is every 
reason to believe, however, as will be shown later, that the history 
is the same except for the difference in the number of chromosomes, 
because heterochromosomes are found very commonly in the O. 
Lamarckiana side of the cross, in the metaphase of the heterotypic 
mitosis, and they doubtless have the same origin as in O. lata. These 
heterochromosomes are the first described in plants, and a dis- 
cussion of their ‘possible significance will be deferred to the end of 
the paper. 
Fig. 23 shows a metaphase of the heterotypic mitosis in O. /aia. 
There are shown twelve chromosomes (some of which are in pairs of 
equal size) and a heterochromosome. Fig. 24 shows two hetero- 
chromosomes of unequal size far out in the cytoplasm. 
Figs. 25 and 26 are from sections of spindles showing the hetero- 
typic mitosis in the O. Lamarckiana hybrid. In jig. 25 the hetero- 
chromosomes are of equal size and are found on the same end of the 
spindle. This condition is very commonly found. In fig. 26 the 
heterochromosomes are in the cytoplasm and not attached to the 
spindle; one of them is larger than the other and they are apparently 
proceeding towards opposite poles of the spindle. 
Fig. 27 is a side view of a spindle showing a small’ chromosome 
out of position near the equatorial plate. A similar body is seen 18 
fig. 26. What significance these may have is not known. Their 
early history has not been observed. They are not ring-shaped, 
like the typical heterochromosomes, but they frequently stain less 
deeply than the regular chromosomes. These bodies were only 
