19"] PACE— PARNASSIA 327 



syner ( 



Fig. 37. — Embryo sac soon after the organization of the egg apparatus, the 

 egg being just under the synergids; only the lower part of it with part of its 

 nucleus can be seen; polars not yet in contact. * 



Fig. 38. — Upper end of sac, slightly older than in preceding figure; one 



synergid has vacuoles above the nucleus, the other has them below it; the 



so-called filiform apparatus beginning to be differentiated near the tip of the 

 synergids. 



Fig. 39. — From older sac; the synergids have unusually large vacuoles, 

 both above the nuclei ; polars are in contact. 



Fig. 40. — The polar nuclei have fused; vacuoles below the nuclei in the 



synergids; the filiform apparatus well developed and forming a caplike 

 structure. 



Fig. 41. — This sac was cut at right angles to the one above, showing 

 the whole of the egg, but only one 

 four-celled sacs. 



Fig. 42. — Upper end of mature embryo sac; the unusual development of 

 the filiform apparatus clearly shown; the inner layer of cells of the integument 

 disintegrating. 



Fig. 43. — Same stage as the preceding, but with the egg apparatus still 

 farther up in the micropylar region; some of the cells of the integument 

 entirely disorganized. 



Fig. 44. — The entire egg apparatus in the micropyle, the adjacent cells of 

 the integument having disappeared and the egg apparatus having a squeezed 

 appearance. 



Fig. 45. — -The upper part of an ovule outlined; the egg apparatus in the 

 micropyle, one synergid lying above the other. 



Fig. 46. — Egg apparatus in the micropyle, but the synergids so pressed 

 together that it is not possible to differentiate them. 



Fig. 47. — A diagram of the upper part of an ovule; one synergid has the 

 upper end entirely out of the ovule, its lower end overlapping slightly the 

 upper part of the other synergid. 



Fig. 48. — The entire egg apparatus just at the entrance of the micropyle, 

 giving the appearance of a pollen tube; the polar nuclei are in contact but 

 have not yet fused. 



Fig. 49.— A few pollen mother cells; in two of these synapsis is perfect, 

 in the others almost so. 



Fig. 50. — The 10 chromosomes may be counted in this pollen mother cell. 



Fig. 51. — Telophase of the first division. 



Fig. 52.— Telophase of the first division in which the 10 chromosomes are 

 still distinct. 



Fig. 53. — Metaphase of the second division, one nucleus showing the 

 spindle and the other being cut parallel with the nuclear plate and showing the 

 !o chromosomes. 





