236 INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



accumulation of them in the region adjacent to the embryo and the 

 two haustoria (Fig. 130/f). Cell formation commences only after 

 64 or more nuclei have been produced and is confined to the upper 

 part, the lower still remaining free nuclear (Fig. 1307). In later 

 stages, therefore, the endosperm shows four distinct regions: micro- 

 pylar haustorium, chalazal haustorium, cellular endosperm, and 

 free nuclear endosperm (Fig. 130/). This last, which Mauritzon 

 calls the "basal apparatus," seems to be an intermediary for con- 



A B C ^^D E 



Fig. 131. Development of endosperm in Crossandra nilotica. A, first division of 

 endosperm mother cell. B, chalazal chamber divided vertically into two cells. 

 C, delimitation of central chamber from micropylar and chalazal haustorium. D,E, 

 cell divisions in central chamber. F, more advanced stage, showing binucleate 

 micropylar haustorium, central chamber with cellular endosperm and embryo, and 

 four-celled chalazal haustorium. (After Mauritzon, 1984.) 



veying food materials from the integument to the cellular portion 

 of the endosperm. An interesting point to be noted is that owing 

 to the continued curvature of the embryo sac, the micropylar and 

 chalazal haustoria come to lie in close proximity to each other. 



Most genera of the family are essentially similar to Ruellia, but 

 a somewhat different condition prevails in Crossandra (Fig. 131), 

 where the divisions in the chalazal haustorium as well as the central 

 chamber are accompanied by wall formation. The former under- 

 goes two vertical divisions to form four cells. In the central cham- 



