Some Recent Work on Hybrids in Plants. 
105 
schizogonous and some homoiogonous the explanation is not nearly 
so satisfactory. Correns further suggests that the division which 
brings about the separation of the characters in the egg cell is the 
one which gives origin to the mother cell of the embryo sac, for his 
observations have shown that the two polar nuclei and the egg 
nucleus are all of the same nature, so that all the eight nuclei of 
the embryo sac must be similar in relation to the “ Anlagen ” of 
the characters considered. In formation of the male cells, however, 
Correns’ view is that the two “ Anlagen ” are not separated till the 
latest possible time, i.e ., the division which gives origin to the 
vegetative and generative cells of the pollen grain. This view is 
based on the fact that in crosses between the red flowered races 
(with greyish-green pollen) and white flowered races (with yellow 
pollen) of Epilobium angustifolium, all the pollen grains in the 
first generation were grey-green like the red flowered parent, and 
not half greyish-green and half white, as would be expected if the 
separation had taken place by means of the division which gives 
origin to the pollen mother-cells. 
Strasburger’s view is, that in the formation of both the male 
and female cells the separation takes place at the time of the 
reduction in number of the chromosomes, for at that time the 
nuclei undergo a profound alteration in form, and at that time only 
is there any histological evidence for such a separation. He also 
suggests that the evidence deduced from the pollen grains of 
Epilobium hybrids is not satisfactory, for it is probabie that the 
walls of the pollen grains are laid down under the influence of the 
nuclei of the tapetal cells, and not under that of the nuclei of the 
pollen grains. The subject is one of considerable difficulty, and 
Corren himself admits that the question is not yet settled. He is 
attempting to obtain more evidence by further experimental work. 
1901 . Bateson, W., Introd. to transl. of Mendel’s Versuche fiber 
Pflanzenhybriden. Jour. Roy. Horticult. Soc., Vol. 26 , pt. 1 . 
1900 , a. Correns, C., G. Mendel’s Regel fiber das Verhalten der 
Nachkommenschaft der Rassenbastarde. Ber d. Deutsch. 
Bot. Ges. Bd. xviii. 
1900 , b - Gregor Mendel’s “Versuche iber die Pflanzen¬ 
hybriden” und die Bestatigung ihrer Ergebnisse durch 
die neuesten Untersuchungen. Botan. Ztg. Bd. 58 , 
Sp. 229 . 
1900 , c. - Ueber Levkoyenbastarde. Zur Kenntniss der 
Grenzen der Mendel’schen Regeln. Botan. Centralbl., Bd. 
84 , s. 97 , 
