Recent Work on the Reduction Division in Plants. 15 
“sporophyte.” Strasburger regards the special case of definite 
duality in the “sporophyte” nuclei as due to the fact that the nuclei 
being derived from neighbouring cells are too closely related to 
attract one another strongly. 
According to the most recent views of the Louvain and Bonn 
Schools, as we have shewn in the first section of this article, the 
full number of somatic chromosomes before the reduction division 
emerge from the reticulum of the resting nucleus, as they do also before 
a vegetative division. But their arrangement differs from that 
characteristic of a vegetative division in that they are grouped in 
pairs, and at the division one of each pair goes off to each daughter 
nucleus. The view which Strasburger holds is that these pairs of 
chromosomes owe their origin to the preceding fertilisation, and 
that one is derived from the male parent and one from the female 
parent, and further that they do not come together accidentally, 
but that “homologous” chromosomes seek one another out. If 
each chromosome is responsible for the transmission of a certain 
number of hereditary qualities we should suppose, for instance, 
that if the plant whose reduction division we are considering was a 
hybrid made by crossing a green-seeded pea with pollen from a pea 
of a pure yellow-seeded race, there would be a certain pair of 
homologous chomosomes present, both bearing the character of 
seed colour, one of which came from the male parent and bears the 
quality of yellowness, and the other from the female parent and 
bears the quality of greenness. In the reduction division the two 
members of this pair of homologous chromosomes would go off 
into the two daughter nuclei. In the succeeding homotype division 
each chromosome would split lengthways into two equivalent halves, 
one of which would go to each spore, so that eventually two of the 
four spores would have chromosomes bearing the quality of “ green 
seededness,” and two, the quality of “ yellow-seededness.” This 
conception is of course purely hypothetical, and we can have no 
rigid demonstration of its truth. But it is at least a good working 
hypothesis, enabling us to harmonise the observed facts of cytology 
with the idea of the “ purity ” of the germ cells with respect to 
certain allelomorphic characters deduced from the experimental 
hybridisation work of Mendel and his followers. 1 If we suppose 
that each chromosome bears a number of hereditary qualities, and 
that it is a matter of chance towards which pole the male and 
female members of each homologous pair move off, we see that 
1 R. C. Punnett. “ Mendelism,” Macmillam and Bowes, 1905. 
* C. Allen, l.c. 
