1004 
Gates. — Somatic Mitoses in Oenothera . 
The two very clear pairs are shown in Fig. 37, the members of each pair 
having the shape of normal somatic chromosomes (i. e. long, somewhat 
curved rods), but lying clearly in longitudinal pairs and oriented quite 
differently from their normal position on the equatorial plate. These are 
separately represented by a and b in Fig. 37 a. The partly fused pair 
are represented by c in Fig. 37 a, while d represents a chromosome which is 
clearly single. 
Critical study of this and one other similar spindle demonstrates that 
a portion, at least, of the chromosomes are closely paired with each other. 
Such cases are evidently rare, and it will require much further study to 
demonstrate the actual fate of the chromosomes in such mitoses. Even the 
loosest pairs are much more closely associated than the pairs of an ordinary 
somatic metaphase (cf. Fig. 37 with Figs. 18, 39, 20), while in several pairs 
the chromosomes appear to be partly fused. Their peculiar orientation on 
the spindle also reminds one of the heterotypic mitosis (Fig. 38) in which 
the chromosomes are always irregularly scattered in the median region of the 
spindle and not in regular alinement. On the whole, it seems probable that 
this pairing in the equatorial region of the spindle (Fig. 37) will be followed 
by the separation of the pairs, and hence by a reduction division. It is 
impossible not to be struck by the numerous differences between this figure 
and a normal somatic metaphase. While the inference that this intimate 
pairing is to be followed by a reduction or segregation division is as yet 
unproven by actual observation, yet it seems more probable than any other 
explanation I can offer. 
Discussion. 
The present paper is meant to be a record of facts rather than a dis- 
cussion of literature, but a few points may be briefly referred to. 
A paired condition of the chromosomes was first found in the somatic 
tissues of plants by Strasburger in 1905. References to subsequent papers, 
showing the undoubted occurrence of regular somatic chromosome pairings, 
were made in my paper on the mode of chromosome reduction (Gates, 
'll a). It is undoubtedly true that this condition in the metaphase of 
each somatic division is widespread in the sporophytic tissues of plants. 
It is obvious from Figs. 4-10 that in the early prophases of sporophytic 
mitoses in Oenothera the chromosomes are at least less evidently paired than 
in the metaphase. Whether they remain associated throughout the whole 
intermitotic period, or whether they go through a regular series of evolu- 
tions leading to fresh pairing in each mitotic cycle, must therefore remain 
undecided, though it is certain that chromosomes which are paired on the 
spindle in metaphase are more likely to be closely associated with each 
other during the passage into the resting condition than those which occupy 
