The Nucleolus and Nuclear Division in the Root- 
Apex of Phaseolus. 
BY 
HAROLD WAGER. 
With Plate V 
T HE great prominence of the nucleolus in nearly all cell-nuclei, its 
definite form, its avidity for aniline dyes, and its behaviour during 
nuclear division led, more than twenty years ago, to the conclusion of 
Strasburger, Flemming, Guignard, and others that it is in some way connected 
with the growth and increased stainability of the chromosomes during the 
division of the nucleus. This view is still maintained by many cytologists, 
although the micro- chemical researches of Zacharias, and the later investiga- 
tions of Strasburger are opposed to it. 
From a series of observations which I have made upon the changes 
which take place in the nucleolus during the process of nuclear division in 
the root-cells of Phaseolus , it appears to me that not only is the nucleolus 
concerned in the formation of the chromosomes, but that there is a definite 
morphological connexion between them. Briefly stated, it is found that 
the nucleolus is intimately connected with the nuclear reticulum ; that it 
contains nearly all the chromatin of the nucleus ; that this is transferred, 
previous to division, into the nuclear thread, which is then segmented into 
chromosomes ; and that, in the reconstitution of the daughter-nuclei, the 
chromosomes become fused into a number of more or less spherical or 
irregular masses which unite to form the daughter-nucleoli 1 . 
Although there are numerous observations which indicate a close 
relationship between nucleoli and chromosomes, the existence of such 
a definite morphological connexion between them had only been previously 
observed in a few cases, of which Spirogyra among plants and Actino- 
sphaerium among animals are the most prominent examples. More 
recently a somewhat similar conclusion has been arrived at in the case of 
the root-cells of Vicia. 
1 These results were stated in a Paper read before Section K at the Bradford meeting of the 
British Association in 1900. See Brit. Ass. Reports, p. 944. 
[Annals of Botany, Vol. XVIII. No. LXIX. January, 1904.] 
