Meiotic Mitoses of Osmunda . iji 
Fig. 64. Superficial section of a nucleus showing the conjunction of filaments. The resulting 
figures are extraordinarily like those of fully organized heterotype chromosomes (cf. Fig. 78) except 
for the slightness of the filaments. Fission is visible in the substance of some of the filaments, in 
others it is closed (H.). 
Fig. 65. Another superficial section of the same stage as Fig. 64. Note the bivalent segment 
on the SE. side showing fission in the independent filaments or segments of univalent spireme, and. 
then their conjunction to form a closed ring showing no fission (H.). 
Fig. 66. 0 . palustris var. aurea. A study of two conjoining filaments twisting over one 
another, showing fission in their free ends (H.). 
Fig. 67. 0 . palustris v ar. uudulata . A nucleus going into second contraction, showing little 
sign of conjunction. This nucleus is taken from the same sporangium as Figs. 68,69, and 71, and 
even from the same microscopic field as Figs. 69 and 71. In Fig. 69 conjunction is advanced, in 
Fig. 71 the nucleus has entered second contraction (H.). 
Fig. 68. As the filaments go into second contraction they show close conjunction in pairs. The 
nucleus has decreased considerably in size (H.). 
Fig. 69. This nucleus is taken from the same sporangium and even from the same microscopic 
field as Fig. 67. Whereas in Fig. 67 the filaments are relatively thick and show little sign of con- 
junction, in Fig. 69 close conjunction in pairs has taken place between most of the segments. Note 
the taut and strained appearance of the conjoining filaments and their precise similarity even to the 
beading (cf. the same phenomenon in the associating threads, Figs. 16, 41, and 46) (H,). 
Fig. 70. 0 . palustris var. aurea. A nucleus going into second contraction. In the centre the 
filaments have collected to form a dense mass. Note the variety in shape, size, and degree of con- 
centration in the filaments not involved in the central mass ; some have conjoined and some are in 
the act of conjoining (H.). 
Fig. 71. 0 . palustris var. undulata. This nucleus is taken from the same sporangium and from 
the same microscopic field as Figs. 67 and 69. The greater part of the nuclear contents are in 
second contraction, the two outlying filaments show a twisted conjunction (H.). 
Fig. 72. Another figure of second contraction. Some of the outstanding bivalent segments 
show a wide separation of their filaments and others close conjunction (H.). 
Fig. 73. A nucleus coming out of second contraction. As the bivalent segments emerge some 
show close conjunction of their univalents, whilst others show stages in the process of disjunction. 
Above the nucleolus on the E. side is an instance of a univalent spireme emerging in detached 
portions which speedily join up end to end r (H.). 
Fig. 74. This nucleus is an example of the second contraction apparently loosening directly into 
fully organized bivalent chromosomes. The two bivalent segments on the W. side of the nucleus 
are disjoining (H.). 
Fig. 75. 0 . palustris var. aurea. In this type of nucleus the bivalent segments come out of 
second contraction as two closely conjoined univalents, and their disjunction closely resembles fission. 
The univalent sides as they disjoin are slight, but speedily concentrate (S.F.). 
Fig. 76. As the univalent chromosomes disjoin they concentrate and stain homogeneously. 
Note the thick bivalent segment running N. and S. which has not yet disjoined into its univalent 
segments (S.F.). 
Fig. 77. On coming out of second contraction, the chromosome segments pass to the periphery 
of the nucleus. Some of the bivalent or heterotype chromosomes are clearly individualized. Fission, 
which is rarely visible at this stage, can be seen in the univalent segment of the chromosome lying 
against the S. boundary of the nucleus (H.). 
Fig. 78. The chromosomes concentrate rapidly. Note the univalents twisting over one another 
in the E. of the nucleus, recalling the twisting over of univalent spiremes (i. e. of filaments) in the 
early conjunction stages (cf. Fig. 64, the segment in the S. of the nucleus) (S.F.). 
Fig. 79. 0 . palustris. Spindle fibres make their appearance from four points in the cytoplasm, 
and the nuclear limiting membrane disappears (S.C.). 
PLATE XI. 
Fig. 80. 0 . palustris var. aurea. The chromosome^ return towards the centre of the nucleus. 
Fission is sometimes visible in the substance of the univalent chromosomes (H.). 
Fig. 81. The spindle fibres invade the nucleus, and the chromosomes concentrate considerably 
and fission closes (H.). 
