Overton—On the Root Tips of Podophyllum Peltatum. 279 
equatorial plate to the poles, numerous more or less irregular 
masses and transparent spots appear (fig. 2). This appearance 
is probably due to the absorption of liquid material and its col¬ 
lection in droplets and masses of irregular shape. These droplets 
may anastomose, giving the appearance shown in these figures. 
This condition gradually increases until conspicuous anastomos¬ 
ing vacuoles appear irregularly distributed in each chromosome, 
(figs. 2, 3, 5, 6, 7). I have, however, never found a line of vac¬ 
uoles arranged regularly along the chromosome axis, such as has 
been described by Gregoire and Wygaerts (’03), Gregoire (’06), 
and more recently by other observers. At their very earliest ap¬ 
pearance some of these vacuoles seem to anastomose, as is shown 
in figures 2 and 3. In the late metaphasic and early anaphasic 
chromosomes the more deeply staining substance or chromatin oc¬ 
curs in granules connected by finer threads, which stain less 
densely and take up the orange in the triple combination like 
linin. From these observations it might appear as though in 
each chromosome the achromatic substance was being dissolved 
or digested or removed by some means, leaving behind a granular 
chromatic substance and a reticulate achromatic portion or linin. 
However, I am inclined to believe that the appearance of vacuoles 
is due to the absorption of liquid substance from without, prob¬ 
ably by osmotic action similar to that described by Lawson (’03, 
’ll, ’12). I am also inclined to look upon the chromosomes as 
osmotic systems, the less dense achromatic substance becoming 
vacuolated and thus separating the denser granular chromatic 
material, which it supports. In figure 3 the chromosomes are 
represented as they appear when stained with the triple stain. 
A less stainable reddish purple substratum is distinctly visible, 
in which appears a more densely staining irregular, granular, 
reticulate substance. By careful study of such preparations one 
can see by focusing that alveoli or bubbles of sap-like material 
also occur in the substratum and that they often anastomose. 
The structure of these chromosomes apparently very strongly 
supports the view that they are to be regarded as a colony of 
granules or discrete particles imbedded in a substratum. From 
the staining reactions the substratum appears to be linin of a 
rather homogeneous or gelatinous consistency. The chromatic 
bodies, which are present in the chromosomes of the equatorial 
plate, and which are divided or separated as the chromosomes are 
divided, are also granular in structure. Undoubtedly these larger 
