678 TRANSACTIONS OF SECTION K. 
direct from the English locality. In no case did these lobes appear in 
any of the rosettes. Instead, a loose rosette is formed, consisting of a few 
leaves of the type which preceded the lobed type of leaf in the tropical 
culture. In many cases, however, no rosette whatever was formed, the 
plants already having a stem several inches high when small seedlings 
three months old. The plants of this series in the tropical culture remained 
in the rosette stage until June 1908, or about ten months. During the 
summer of 1908 they sent up tall, slim stalks, branching very little except 
at the top. 
Incidentally it might be said that there is no tendency in the offspring 
of the tropical culture to inherit the tendency to produce the type of rosette 
leaf with basal lobes. 
4. The Organisation and Reconstruction of the Nuclei in the Root-tips 
of Podophyllum peltatum. By Professor James Bertram OVvERTON. 
Although nuclear divisions have been frequently studied, a detailed 
investigation of the behaviour of the chromosomes during rest has, until 
recently, been largely neglected. A number of valuable papers have 
appeared, notably, those of Von Wisselingh, Grégoire, and his students, 
Haecker, Strasburger, and Bonnevie, so that general interest has increased. 
Most authors hold that the chromatin is the bearer of the hereditary 
qualities. In the resting nucleus there appear two stainable substances, 
the linin framework, in which the more stainable chromatic corpuscles are 
. Impregnated or supported. When the chromosomes become visible these 
corpuscles, or whatever they may be called, become arranged in linear 
series into a ribbon or spirem. By a fission of these bodies and of the sub- 
stratum a perfect division of the hereditary qualities results. Grégoire 
admits the presence of two substances, but maintains that the chromatin 
does not exist as granules, but that it impregnates the linin. He finds 
the reticulum equally stained, except at the junctures in the young regions 
of the root-tip, and therefore concludes that the chromatin entirely im- 
pregnates the linin in these nuclei. In older regions one can recognise true 
chromatin spheres, resulting simply by a massing at certain points. In 
the spirem he believes the so-called chromomeres are only the nodal struc- 
tures due to alveolisation, the whole band being chromatic with denser 
portions. 
The reticulum of the resting nucleus results, according to Gégoire, by 
the lateral anastomosing of the telophase chromosomes. These anastomoses 
arise as marginal portions of the chromosomes, which are at first always in 
contact, and by the transformation of each chromosome, by means of a 
gradual alveolisation, into alveolar reticulate bands or elementary reticula. 
The final nuclear reticulum, therefore, is composed of a number of elemen- 
tary reticula in juxtaposition. During the prophases a recondensation 
occurs to form the chromosomes of division. This interpretation has been 
confirmed by Kowalski, Berghs, Ulano, Haecker, and the Schreiners. 
I have endeavoured to follow in detail the changes which the telophase 
chromosomes undergo during their passage into the resting nucleus, and to 
follow carefully their structure and arrangement in the resting nuclei of the 
root-tips of Podophyllum peltatum, and also to determine how the visible 
chromosomes are reformed preparatory to division. 
During the passage of the chromosomes from the equatorial plate to the 
poles they become more or less irregularly vacuolated, appearing more 
transparent in spots. This appearance gradually increases until conspicuous 
anastomosing vacuoles appear on the inside. I have never found the 
chromosomes so completely massed or crowded as described by some authors 
for other plants. The chromosomes often touch each other laterally at 
