it a a al a el ee ee a ee ee 
Pe ee ee Wee 
1899] STUDIES ON REDUCTION IN PLANTS 5 
The chromosomes are marked off by the band separating into 
sixteen segments. So far as could be determined, this number 
is quite constant. The segments are not formed by an abrupt 
division of the spirem, but it appears as if the chromatin masses 
by shortening unite themselves into elongated areas, which are 
connected for a time by two delicate threads representing the 
original line of longitudinal division. The chromosomes lie 
around the periphery of the nuclear cavity and are quite variable 
in form; this is due to variations in the extent to which longi- 
tudinal fission has proceeded. In a few, longitudinal fission 
is complete, and a pair of long knotted rods is present. In 
others, there is a slight connection at one end or near the middle 
by the fusion of adjacent chromatin. In others, one or both 
ends of the flattened chromosome are indented or forked; in the 
latter case figures approaching the letters Y or X are formed. In 
many of the chromosomes the line of fission is shown by one 
or two small rounded openings or narrow open slits near the 
middle or near the ends; or the opening is long and extends 
from end to end, individuals of the pair being connected only at 
the end, thus resembling long irregular chain links. Some of 
the individuals of the pair lie parallel ; others are separated more 
or less at the middle, when quite well defined rifts are formed. 
Still others resemble chain links twisted half way around, thus 
presenting a figure 8 appearance (jig. 6). 
The length of the chromosomes is now from one third to one 
half or more the diameter of the nuclear cavity, and they show 
the irregularities presented by the spirem band, being knotted or 
angular along the edges or at the end. Delicate linin threads 
are often still attached at the knotted or angular enlargements. 
The chromosomes now shorten, the chromatin becoming 
massed together, until their length is from one sixth to one fourth 
the diameter of the nuclear cavity. A larger proportion of them 
have now opened out in the middle in the form of rings, and, while 
they have shortened in length, their breadth is about the same as 
formerly, or they may bea little broader. This gives a more per- 
fect ring form, but the chromosome is still somewhat longer than its 
