Meiotic Mitoses of Osmunda. 169 
Fig. 24. The daughter chromosomes show no fission as they proceed to their respective poles 
(S.F.). 
Fig. 25. 0. palustris. Telophase of the last archesporial division before the heterotype pro- 
phase. The chromosome segments are splitting apart into halves (threads) ; each thread may be 
more or less homogeneous, or beaded (S.M.). 
Fig. 26. The separation of the chromosome halves or threads has proceeded slightly farther ; 
note the clear spaces round the nucleoli (S.M.). 
Fig. 27. Superficial view of a portion of a nucleus at this stage; fine strands join the severally 
paired segments, the skeletons of the former chromosomes (S.M.). 
Fig. 28. Very late telophase. The chromosomes are now no longer recognizable owing to the 
dispersal of their halves, although parallel fine threads are still to be seen. The more aggregated 
appearance of the chromatin is due to the fixative used (S.C.). 
Fig. 29. 0. palustris var. aurea. Typical late telophase showing the spaces round the two 
nucleoli, the threads having completely separated and fragmented into beads (S.F.). 
Fig. 30 A nucleus showing both telophase and prophase characters, evidently passing directly 
from the telophase of the last archesporial division into the heterotype prophase (see also Figs. 31 
and 32). The beaded parallel threads and the presence of three nucleoli are suggestive of telophase, 
whilst the large size and generally active appearance of the nucleus denote prophase (S.F.), 
PLATE IX. 
Fig. 31. Superficial section of a nucleus in the same stage as Fig. 30 showing strikingly paired 
threads (S.F.). 
Fig. 32. 0. regalis. Another nucleus which cannot be definitely described as either in telophase 
or in prophase. Although actually only one pair of parallel beaded threads is to be seen (in the S. 
of the nucleus), yet there are indications of parallel arrangements in the groupings of the beads and 
in the disposition of the fine linin threads (A. A.). 
Fig. 33. 0 . palustris var. aurea. A transitional nucleus passing directly from telophase of the 
last archesporial division into the heterotype prophase without an intermediate rest. The nucleus 
is larger than in rest (Fig. 34) and is active in appearance and stains sharply. Three nucleoli are 
present ; the chromatic beads are larger than those of early prophase (Fig. 36) ; parallel arrange- 
ments of beads and threads are to be seen. It is impossible to designate such a nucleus as being 
either in telophase or in prophase (S.F.). 
Fig. 34. The resting stage between the last archesporial division and the heterotype prophase. 
The nucleus shows a colourless reticulum with the chromatin concentrated in the nucleoli (S.F.). 
Fig. 35- Very early prophase ; note the somewhat more sharply staining reticulum and the few 
chromatic granules (S.F.). 
Fig. 36. A nucleus definitely in prophase. The reticulum is more defined, consisting of fine 
threads with chromatic beads at the junction of the meshes. A few of the linin threads tend to run 
parallel to one another, and the granules to group themselves in pairs and fours (cf. Fig. 10). This 
is the first indication of the reassociaiion of the chromosome halves (threads) which separated in the 
preceding telophase (Figs. 25, 26, and 27) (S.F.). 
Fig- 37. The nucleus has enlarged considerably. The reticulum gradually opens out to form 
beaded threads, and these threads tend to run in pairs, each thread representing half a univalent 
chromosome of the preceding telophase. As the nuclei proceed towards synapsis the pairing of these 
half univalent spiremes (threads) preparatory to their close association to form the entire univalent 
spireme (filament) becomes increasingly conspicuous (S.F.). 
Fig. 38. The linin threads become chromatic and hence definitely spireme in character (S.F.). 
Fig. 39. The spireme shows a very striking pairing of its lengths (S F.). 
Fig. 40. The pairing becomes more accentuated, and in some parts has resulted in the close 
association of the two threads to form the entire univalent spireme or filament (S.F.). 
Fig. 41. Note the lengths of paired threads connected at intervals by paired beads. There is 
a slight withdrawal of the nuclear contents in the NW. portion of the periphery preparatory for 
synapsis (S.F.). 
Fig. 42. The spireme thread retreats from the nuclear periphery and is thrown into loops which 
lie free in the nuclear cavity ; towards the margins parallel arrangements are visible (S.F.). 
Fig* 43* A superficial section of a nucleus in the same stage as Fig. 42, showing two associating 
lengths of spireme thread twisting over one another (S.F.). 
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