140 INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



in Psychotria (Fagerlind, 1937) starch appears at the dyad cell 

 stage; in Castalia (Cook, 1902), Acacia (Guignard, 1881), Sedum 

 (D'Hubert, 1896), Pentas, Richardsonia, and Cephalantus (Fager- 

 lind, 1937) at the functioning megaspore stage; in Portulaca oleracea 

 (Cooper, 1940) at the binucleate stage; and in Corchorus trilocularis 

 (Stenar, 19256), Cynanchum acutum (Francini, 1927), and Medicago 

 saliva (Cooper, 19356) at the 4-nucleate stage. In the majority of 



Fig. 91. Embryo sacs of Acacia baileyana, showing starch grains. A\,Ai, succes- 

 sive sections of unfertilized embryo sac. B, postfertilization stage. (After New- 

 man, 1934.) 



plants, however, the starch appears when the embryo sac is mature 

 and reaches a maximum shortly after fertilization, gradually de- 

 creasing in postfertilization stages. Xyris indica (Weinzieher, 

 1914), Acacia baileyana (Newman, 1934) (Fig. 91), and Petunia 

 (Cooper, 1946) (Fig. 112) are peculiar in having large quantities 

 of starch even during endosperm formation. 



A few cases are on record in which the starch occurs not merely 

 in the cavity of the embryo sac but also in the cells of the egg ap- 



