A critical study of thc oytology of Crepis virens. 
105 
honiology betweeii the chromosomes of tlie tclopliase of tlie last arche- 
sporial division, and the chromatic bodics of the succceding heterotype 
prophase, and States that he has no donbt but that these chi’omatic 
bodies are derived froin the preceding mitosis (p. 944). On the other 
hand Nakao (37) found that in certain cereals, the nncleus, in the phase 
preceding the so-called resting stage, has no definite structure, bnt stains 
soniewhat inore deeply than the surrounding cytoplasm, and posseses 
one large nucleolus (37, PI. X, fig. 1); it was only snbseqnently that 
the chromatic bodies niade their appearance. A somewhat similar con- 
dition prevails in some of the Priniulas (10). 
Resting stage. 
When the ceU wall has beeil laid down between the two daiighter 
nuclei, and the iinclei have increased in size and beconie more or less 
spherical, theii’ fine granulär character becomes transformed into one 
more typical of rest. The chromatin tends to concentrate at fii’st into 
small granules, and these gradually coUect together in groups to form 
more definite chromatic aggregations (fig. 4 and 5). The rounded chroni- 
atic bodies which are thus formed take a deep stain, and are sharply de- 
fined from the almost colonrless and finely granulär reticulum in which 
they are suspended. 
Care has been taken, throughout the study of those phases concerned 
with chromatic bodies, to restrict the examination exclusively to whole 
nuclei, that is to say to nuclei untouched by the razor. Scctions 6 /< in 
thickness give a large proportion of such nuclei. Perhaps it will not be 
inopportune to emphasize the extreme importance, when counting ‘pro- 
chromosomes’, of ascertaining that the nuclei in question are really entire. 
In published records this point is constantly ignored. 
It is probably impossible to find complete resting nuclei m the rapidly 
dividing archesporial tissue. In typical resting nuclei, as exemplified 
by those of the tapetuni (PI. X, figs. 118, 119, and 120) of an older anther, 
the linin reticulum is colonrless, and niost of the chromatin seems to be 
confined to the few chromatic bodies and to the nucleolus. On the other 
hand, in the nuclei of the archesporium which exhibit the nearest approach 
to rest (PI. VIII, figs. 5 and 6), the linin, though colonrless, is definitely 
recognisable, and the chromatin may not be exclusively concentrated 
in the chromatic bodies but may also be present in the form of numerous 
small beads. Laibach (26) has similarly shovm in some of the Cruciferae 
that only a portion of the chromatin may be collected in the “Körnchen”, 
the remainder being distributed throughout the reticulum giving it a 
