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INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



mains can be recognized for a considerable time (Fig. 60B,C; Fig. 

 61A-C). In Balanophora even the dyad cells show a marked dif- 

 ference in size, the micropylar cell being much larger than the 

 chalazal (Fig. GO A). At the 2- or 4-nucleate stage a tubular out- 



C ' — ' F v G 



Fig. 60. Development of embryo sac in Balanophora elongata. A, dyad cells 

 undergoing second meiotic division. B, functioning megaspore, with remains of 

 three degenerating megaspores at its base. C,D, two-nucleate embryo sacs; note 

 lateral outgrowth from basal part of embryo sac in D. E, four-nucleate embryo 

 sac. F, eight-nucleate embryo sac; note that egg apparatus has organized in 

 morphologically lower end of embryo sac. G, older stage of same, showing fusion 

 of four nuclei at antipodal end. (After Fagerlind, 1945a.) 



growth arises from the embryo sac and then grows upward. In 

 Balanophora it originates near the basal end of the sac (Fig. 60D) 

 and in Langsdorffia near its apical end (Fig. 61 A). In both cases 

 it grows very quickly and soon comes to lie at a higher level than 

 the originally upper end of the embryo sac (Fig. QOE, Fig. 61B,C). 

 The 4 nuclei of the sac now undergo the last division to form the 



