1914] McAllister— embryo sac of convallariaceae i« 



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Fig. 32. — The inner daughter cell has divided to form 2 cells which are 

 separated by a definite and complete cell plate; the outer daughter cell now ' 

 but a disorganized mass. 



Fig. 33. — The 2 daughter cells of the second division widely separated by 

 a split cell plate. 



Fig. 34. — The nuclei of 2 fully separated inner daughter cells have divided, 

 thus forming 2 binucleate cells; since both inner cells are to be regarded as 

 megaspores, these 2 binucleate cells are immature female gametophytes. 



Fig. 35. — A binucleate embryo sac with no trace of cell membranes. 



Fig. 36. — A 4-nucleate stage of the embryo sac. 



Fig. 37. — A fully formed embryo sac. 



Medeola virginica 



Fig. 38. — A megasporangium showing a single hypodermal megaspore 

 mother cell, in the synaptic stage; magnification but half that of the other 

 figures. 



Fig. 39. — The first division of the mother cell; a conspicuous though 

 incomplete cell plate is present. 



Fig. 40. — The second division of the mother cell; the cell plate of the first 

 division no longer visible; those of the second division very conspicuous but 

 not sharply defined; the chalazal nuclei are practically equal. 



Fig. 41. — A slightly earlier phase in which the inner pair of nuclei has a 

 small inner (chalazal) nucleus and a large outer nucleus. 



Fig. 42. — An embryo sac in which the inner pair of nuclei is very unequal; 

 the inner nucleus stains deeply as though degenerating. 



Fig. 43. — The third division; 2 small nuclei and 2 large ones in the antip- 

 odal end of the sac as a result of the unequal division of the antipodal nucleus 

 in the previous division; the cell membranes of the second division still visible. 



Fig. 44.— Antipodal region of the embryo sac showing 3 equal antipodal 

 cells and the single fusion nucleus, fusion of the polar nuclei having taken place. 



Polygonatum commutatum 



Fig. 45. — Two hypodermal mother cells in a single nucellus. 

 Fig. 46. — -A single mother cell showing two layers of cells between it and 

 the epidermis. 



Fig. 47. — Two daughter cells of the first division of the mother cell. 

 Fig. 48. — An axial row of 4 megaspores. 



Fig. 49. — The enlarged inner megaspore and the disintegrated remnants 

 of the outer three. 



Fig. 50. — First division of the megaspore. 



Fig. 51. — Binucleate embryo sac with a single large central vacuole. 



Fig. 52. — Mature embryo sac; the polar nuclei not yet fused. 



