THE ENDOSPERM 



239 



endosperm mother cell is transverse, resulting in the formation of 

 the two primary chambers, micropylar and chalazal. The second is 

 vertical, but in both chambers the walls are incomplete and do not 

 extend to the two poles of the embryo sac. The third division is 



E 



Fig. 133. Development of endosperm in Lobelia amoena. A, l.s. ovule, showing 

 four-celled stage of endosperm. B, transverse division in some of the endosperm 

 cells. C, laying down of micropjdar and chalazal haustoria. D,E, more advanced 

 stages, showing multiplication of cells of endosperm, the enlarging haustoria, and 

 the developing embryo. {After Hewitt, 1939.) 



transverse and takes place simultaneously in both the upper and 

 the lower chambers. Thus the embryo sac now consists of a central 

 portion of four cells, two contributed by the upper and two by the 

 lower primary chamber, and two terminal portions with two nuclei 



