Rit Landbúnaðardeildar : B-flokkur - 01.05.1947, Síða 10

8
At anaphase-I and metaphase-II the distribution of chromosomes was
studied in 250 PMC’s. In 211 cells it was found to be 18:18. (Fig. 4), in
23 cells it was 17 : 19 (Fig. 5), in 9 cells it was 16 : 20 and in 7 cells it
was 17:1: 18, i.e. one chromosome was found lagg'ing between the plates.
Thus, in as many as 15.6% of the cells the number of chromosomes at
anaphase-I and metaphase-II is not 18 in both the plates.
Inversion bridges with fragments (Fig. 6) were relatively common,
having been observed in all the plants studied in a frequency varying
between 0.3 and 7.1%. As the size of the fragment was clearly different
in different plants it might be considered that more than one inversion is
met with in the material studied.
The distribution of chromosomes at anaphase-II was found to be
somewhat irregular in some of the ptants investigated although only a
few exact countings were made. In the letrad stage soine irregularities
as e.g. dyads and pentads were observed.
TABLE 1. The chromosome pairing in Cakile edentula.
Configuration.
liv + 16n
2IV +
3iv + 12n
4IV + 1°II
5IV + 8II
6IV + 6II
liv + 15II + 2I
2IV+ 1III + 1 2II +
3IV + 1 1II + 2I
Number of PMC.
15
48
66
93
42
24
2
1
3
Total: 294 cells.
Average frequency of quadrivalents per cell: M ± m = 3.56 ± 0.01.
3, Fertility of pollen grains.
The apparent fertility of pollen grains of C. edentula was studied in
aceto-carmine-glycerine on material froni Suðurnes at Seltjarnarnes in
the vicinity of Reykjavík. The percentage of filled pollen grains observed
in 610 different plants is given in Table 2. The average fertility was
84.38% of filled pollen grains.