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AMERICAN JOURNAL OF BOTANY 
[Vol. io, 
ing to the focal depth at which the bodies are observed. (Compare the 
photographs on Plate XXX.) 
This composite construction of the chromosome holds true for the 
chromosomes of the homoeotypic divisions. These chromosomes appear 
more gracefully modeled than do those of the heterotypic spindle. Figure 
5 is a free-hand drawing of one of the second-division chromosomes, and 
is the same one as a, figure 6, Plate XXIX. The relations of the chromo- 
meres seem to be the same here as already discussed, but they can be made 
out only under the most favorable conditions. 
Figure 7 represents two free-hand drawings of the same chromosome. 
The upper drawing is of the top focus; the lower is at the bottom focus. 
From these drawings one obtains an idea of the irregularly shaped chromo- 
meres that are sometimes encountered. One is able to trace the shapes 
of the bodies through the linin mass from top to bottom. The clear space 
or constriction in the center resulted from applying pressure to the cover 
glass while teasing the chromosomes into the suspension fluid, so that too 
much importance may not be attached to forms such as these. 
The linin substratum seems to be of a jelly-like consistency, and if 
the chromosomes are crushed the chromomeres often fuse in a more or 
less solid mass. Varying degrees of contact from complete independence 
to complete fusion may be observed in cells injured by dissection instru¬ 
ments. 
A Correlation of these Findings with Others of a Similar Nature 
Balbiani (1881) first called attention to disks of chromatin in the nuclear 
filaments of salivary-gland cells in Chironomus larvae. These had been 
fixed in a mixture of \ percent chromic- and acetic-acid solutions. The 
glands were treated with the reagent for a few minutes, washed in distilled 
water, and, after staining with methyl green, were mounted in glycerin. 
A considerable amount of work on the same material has been done, 
principally by Lydig (1883), Carnoy (1884), Korschelt (1884), Erhard 
(1910), von Herwerden (1910), Bolsius (1911), and Alverdes (1912). All 
the authors agree on the compound nature of the threads but differ as to 
the details. 
Balbiani considered these chromosome constituents to be disks arranged 
in a series with clear spaces filled with Zwischensubstanz separating them. 
He likens them to a series of red blood corpuscles placed end to end. 
Lydig (1883) held that the dark transverse segments of the chromosome 
are themselves made up of smaller bodies, and that the lines separating 
these may make up something like longitudinal lines of division in the 
chromatic material. It may be noted that these more irregular lines of 
division agree in part with my findings as shown by several figures of Plates 
XXIX and XXX. 
Korschelt held that the cross and other markings are due merely to 
the wrinkling of the chromosome surface. 
