74 INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



land, 1938), Cyathula (Kajale, 1940), Costus (Banerji, 1940), and 

 Desmodium (Pantulu, 1941). 



An isobilateral or a tetrahedral arrangement of megaspores is 

 very rare and has been reported only as an abnormality (Fig. 52C). 



Fig. 51. Part of ovule of Casuarina montana, showing multiple archesporium. 

 Some of the sporogenous cells are in prophase; others have gone through meiotic 

 divisions to form megaspore tetrads; and a few have formed two- and four-nucleate 

 embryo sacs. Note that in tetrad at upper end, all megaspores are binucleate. 

 {After Swamy, 1948.) 



