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INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



stein, 1926) and Melilotus, (Cooper, 1933) the embryo sac ruptures 

 the nucellar epidermis and grows beyond it, so that more than one- 

 third of it lies in direct contact with the cells lining the micropy- 

 lar canal. In Arechavaletaia (Ventura, 1937) and Kirengeshoma 

 (Mauritzon, 1939) it protrudes out of the endostome and comes to 

 lie in the exostome. In Philadelphus (Mauritzon, 1933), Thesium 

 (Schulle, 1933), Galium (Fagerlind, 1937), Utricularia (Kausik, 



Fig. 93. Some instances of embryo sacs protruding into and beyond micropyle. 

 A, Phaseolus vulgaris, upward elongation of embryo sac, resulting in rupture of 

 nucellar tissue; nucellar epidermis is intact, however, at apex of embryo sac. (After 

 Weinstein, 1926.) B, Torenia hirsuta, embryo sac protruding out of micropyle. 

 (After Krishna Iyengar, 1941.) C, Philadelphus coronarius, embryo sac protruding 

 out of micropyle. (After Mauritzon, 1933.) D, Galium lucidum, one embryo sac 

 completely outside micropyle; another in position, but in process of degeneration. 

 (After Fagerlind, 1937.) 



1938), and certain members of the Scrophulariaceae like Vandellia 

 and Torenia (Krishna Iyengar, 1940, 1941) the nucellus breaks 

 down completely at a rather early stage and the naked embryo sac 

 protrudes out of the ovule, establishing direct contact with the 

 placenta and digesting its way into the tissue of the latter (Fig. 

 93B-D). Strangest of all are some genera of the Loranthaceae, 

 like Scurrula and Dendrophthoe (Rauch, 1936; Singh, 1950), in which 

 ovules and integuments are absent in the usual sense and the embryo 

 sacs undergo a remarkable elongation toward both the top and the 

 bottom. At the lower end they are soon stopped by a pad of col- 



