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328
ARTUR HÅKANSSON
A case where in the presence of il s the l"s get a stronger tendencv
to divide at anaphase 1 seems lo be Alopecurus myosuroides (Johnsson
1944). Here liiere is a strain with absolute asyndesis and with
non-division of the I’s. A few plants formed a number of Il’s (1—6 II)
and in such plants division of one or a few I’s was ollen observed,
in no p.m.c., however, all I’s were divided. The regulär division of
deflexa- or Bottne-1 that were in the (»late in the triploid hybrids also
shows infhience from the I I’s ön the behaviour of I’s.
In the hybrid G. def/exaXG. Bottae with in most p.m.c.’s 18 I the
small Bottne I’s predominantly occupy the centre of the equatorial
plate, the larger deflexa l’s as a rule are möre peripher (H.. 1943 b).
In G. Whitneyi, 4nXG. Bottae the small Bottae I’s lie peripher, the
large Whitneyi Il’s occupying the centre of the plate. This difference in
the position of the Bottae I’s in the two hybrids is no doubl due to the
fact, that the Whitneyi H"s, when the membrane of the diakinesis
nucleus disappears, immediately take a position in the centre, and
eon-sequently the I s must lake möre peripher positions.
In the hybrid G. deflexaXG. Bottae other differences in the
behaviour of large and small I’s seemed to be manifest. Of ten some I’s
did not reach Ibe equatorial plate, and in most cases it was Bottae I’s
that were lying outside the plate. Rarely an I was divided, in Ihe few
cases observed the divided I was a Bottae-1. 1 hoped, that a study
of the behaviour of the I’s in the triploid Whitneyi hybrids with a
möre regulär meiosis could give some information concerning the
behaviour of small and large I’s. As it now turned out, certain stages
of the meiosis in G. Whitneyi, 4nXG. Bottae were rauch disturbed in
comparison with the same stages in G. Whitneyi, 4nXG. deflexa. To
detect differences in the behaviour of the I’s in Ihe two hybrids is
therefore rather difficult.
The rather pronounced disturbances at anaphase 1 were unexpected
because such disturbances were insignificant in Whitneyi, 4nXdeflexa,
and, as already mentioned, G. deflexa and G. Bottae are considered lo
be closely related, I bus deflexa was by Hitchcock interpreted as a
sub-species of G. Bottae. Hut perhaps Ihev are not verv closely related. The
hybrid G. deflexaXG. Bottae shows a strong asyndesis, and this speaks
againsl a closer connection between these species. Il is true, the
asyndesis was attributed to the great difference in size between
»homo-logous» chromosomes in the hybrid; but perhaps one should not lake
the close relation of G. deflexa and G. Bottae for granled, Ihe möre
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