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INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



micropylar chamber shows active nuclear divisions and soon gives 

 rise to two tubular outgrowths (one on each side of the chalazal 

 chamber) which grow downward and invade the tissues of the 

 chalaza (Fig. 142 1-L). Subsequently the main body of the cham- 

 ber also elongates and fuses with the two haustoria to form a con- 

 tinuous mass of endosperm cells with the chalazal chamber still 

 recognizable at the base (Fig. 142 A-F). 



D 



E 



F 



Fig. 141. Modifications of Helobial endosperm as illustrated by Anthericum 

 ramosum, Ixolirion montanum, and Echium plantagineum. A, Anthericum, l.s. 

 ovule showing mature embryo sac; secondary nucleus lies in diverticulum. B, 

 same, l.s. nucellus, showing further development of diverticulum and formation 

 of endosperm of Helobial type. {After Schnarf, 1928b.) C, Ixolirion, embryo sac, 

 showing laterally situated chalazal chamber; only two of the antipodal cells are 

 seen in section. {After Stenar, 1925.) D, Echium, embryo sac, showing' laterally 

 placed chalazal chamber consisting of two binucleate cells. E,F, more advanced 

 stages, showing formation of several free nuclei in "central" as well as "lateral" 

 chambers. {After Svensson, 192o.) 



