344 
LESTER W. SHARP 
apparently become more numerous, and the alveolation of the chromo- 
somes becomes more complete (fig. lo). The chromosomes at this time 
usually show a distinct polarity in their arrangement, as represented semi- 
diagrammatically in figure 8. As the vacuoles within the chromosome in- 
crease in size and number, their boundaries at the margin of the chromo- 
some break down, allowing them to become continuous with the nuclear 
cavity. In this way the alveolar or vacuolate condition passes into a retic- 
ular one; each chromosome becomes an irregular netlike structure which 
is in no sense double. All of them together, with their connecting anas- 
tomoses, constitute the common reticulum of the late telophase and inter- 
phase or resting stages. The limits of the constituent chromosomes remain 
visible until a comparatively late stage (fig. ii). 
Interphase and Rest. The degree to which the telophasic transforma- 
tion is carried varies considerably in different nuclei, the amount of change 
being correlated with the rapidity with which the mitoses succeed one 
another. In the most active part of the root meristem it seems evident 
that the transformation may go no further than the stage represented in 
figure II, the prophasic changes of the next mitosis setting in at once. In 
such an event the chromatin passes directly from the stage of figure ii 
(telophase) to that of figure 14 (prophase) : the anastomoses connecting 
the reticulate chromosomes begin to break down while the chromosomes 
are yet distinguishable, so that there is no time between the successive 
mitoses at which the limits of the chromosomes cannot be seen. It is plain 
that in such cases the structural identity of the chromosomes is not lost 
during the interphase. 
The interphase condition most commonly found in the root meristem is 
that shown in figure 12. Here the telophasic transformation has been 
carried much further; the anastomoses for the most part cannot be dis- 
tinguished from the other fine strands of the reticulate chromosomes, and 
the limits of the chromosomes cannot be made out with any certainty. 
Here and there are lighter regions which probably represent boundaries 
between the constituent chromosomes, and if the prophasic changes were 
to begin at this time the reticulum would almost surely break down along 
these lines. The chromatin may apparently continue in this state for 
some time, so it may properly be said to be in the ''resting" condition. 
In older tissue, but only rarely in the root meristem, the telophasic 
changes continue until tiie nucleus has the structure shown in figure 13. 
The chromosomes, all visible traces of whose limits have now been lost, 
form a common chromatic reticulum of very fine texture. Such a reticulum 
is ordinarily described as being made up of "granules of chromatin carried 
on a supporting network," and so it surely appears if not sharply stained 
or if viewed through lenses of insufficient resolving power. But careful 
examination, together with a comparison of the successive stages of the 
telophase, lead to a different interpretation. Since the structure of the 
