Cardiff: Synapsis and reduction 



305 



Figure 33. Prophase of first division ; eleven chromosomes most of which show 

 bivalent character. 



P'lGURE 34. Pole view of early metaphase of first division ; different sized chro- 

 mosomes. 



Figure 35. Equatorial view of metaphase of first division ; only part of chromo- 

 somes represented. 



Salomonia bi flora 



Figure 36. Early mother-cell ; chromatin threads just forming. 

 Figure 37. Section of early mother-cell nucleus ; formation of threads and ar- 

 rangement near nuclear wall. 



Figures 38 and 39. Sections of early presynaptic 



nuclei ; beginning of parallel arrangement of threads. 



Figure 40. Section of presynaptic nucleus ; chro- 

 momeres increasing in size and activity ; parallel threads. 



Figures 41 and 42. Presynaptic nucleus, chromomeres 

 beginning to fuse. 



Figure 43. Nucleus just previous to beginning of con- 

 traction of chromatin thread into knot; threads nearly all 

 show paired character ; chromomeres smaller when threads 

 are apart as at a. Figure 43 



Figure 44. Mother-cell just previous to synapsis ; 

 threads contracting to form knot ; cell rounded off ; cytoplasm showing many deeply 

 staining granules. 



Figure 45. Synapsis. 



Figure 46. Synapsis with portions of threads projecting from side of knot show- 

 ing bivalent character. 



Figure 47. Postsynaptic nucleus. 



Figure 48. Postsynaptic nucleus ; beginning of transverse division, a. 



Figure 49. Prophase of first division ; seven chromosomes ; smaller bodies, a, 

 probably a disorganizing nucleolus. 



Figure 50. Metaphase of first division ; heterotropic chromosome at one pole. 



Ginkgo biloba 



Figure 52. Early mother-cell; beginning of formation of threads; several 

 nucleoli. 



Figure 53. Section of early mother-cell ; beginning 

 of parallel arrangement of chromatin threads ; small amount 

 of cytoplasm. 



Figure 54. Section of presynaptic nucleus ; threads 

 thickening ; parts of pairs moving closer together. 



Figure 55. Nucleus just previous to synapsis ; project- 

 ing threads showing pairing. 



FIGURES 56 and 57. Portions of threads cut from per- 

 iphery of close synaptic knots showing bivalent character. 



Figure 58. Nucleus in synapsis. 



Figure 59. Portions of nucleus as the thread is disentangling from synaptic knot 5 



bivalent character shown in places. 



Figure 60. Late prophase of first division; twelve chromosomes; nearly all 



chromosomes showing bivalent character. 



Figure 54 



