Davis, — Cy to logical Studies on Oenothera, I. 567 
study of Oenothera grandiflora presents conditions that the writer cannot 
bring into harmony with their conclusions. Our present information for this 
type strongly indicates a pairing of the sporophytic chromosomes according 
to the method held by Farmer and Moore. The writer is disinclined to 
believe that so important a process in the life-history of plants as that of 
chromosome reduction is likely to be effected by two methods so diverse 
as those held by the opposing groups of investigators mentioned above, but 
there is at present a conflict of such apparently good evidence that one 
may well hesitate before taking a positive position. The conditions in 
Oenothera grandiflora that seem to require the explanation of chromosome 
association advanced by Farmer and Moore may be summarized as 
follows :• — 
1. The arrangement of the chromatic material during synapsis is 
characterized by the presence of several loops extending freely into the 
nuclear cavity from the synaptic knot as a centre (Figs. 19-23). 
2. These free loops thicken as synapsis proceeds, and it seems clear 
that some of the ring-shaped bivalent chromosomes are formed directly 
from them. 
3. The fact that the ring-shaped bivalent chromosomes are sometimes 
linked together is difficult to understand except on the theory that they 
have become so associated by the segmentation of a much-coiled spirem the 
loops of which were interlaced. 
Summary. 
1. The vegetative (somatic) nucleus contains chromatic bodies that 
frequently approximate the number of the sporophytic chromosomes, which 
is fourteen. It seems probable that they are prochromosomes. These 
bodies in the resting nucleus are connected by a delicate open network 
which becomes much more conspicuous and denser before the development 
of the spirem of the vegetative mitoses. 
2. The spirem arises from this reticulum which later disappears, after 
which the spirem may be followed for great lengths as a single thread. 
Fourteen chromosomes in the form of long rods variously bent are formed 
by the cross-segmentation of the spirem. 
3. Following the vegetative mitoses, the chromosomes become distri- 
buted through the nuclear cavity of the resting nuclei, where they take on 
the form of chromatic bodies. 
4. Previous to synapsis the nucleus becomes filled with a close reticulum 
during the formation of which the chromatic bodies lose their rounded form 
and could not be followed. 
5. Synapsis consists of a general slow contraction of the reticulum 
away from the nuclear membrane, a contraction that carries most of the 
