Roscndahl: embryology of symplocarpus foetidus. 5 



the base of the ovule (Fig. 36, PI. III). The inner integument is 

 quickly consumed, and the outer meets the same fate as soon as 

 the growing endosperm comes in contact with it. Thereupon the 

 basal portion of the ovule is attacked. 



The early behavior of the antipodal cells seems subject to some 

 variation. In embryo-sacs where no embryo or endosperm develop- 

 ment takes place, and this happens to be the case with a large num- 

 ber of the ovules examined, the antipodal cells begin to shrink and 

 disintegrate before the egg apparatus shows any such signs. In 

 rare cases on the other hand the antipodals increase greatly in size 

 before any signs of fertilization become evident (Fig. 18, PI, I). 

 As soon as the embryo begins to segment and endosperm to form, 

 the normal behavior of the antipodal cells is to begin dividing and to 

 show signs of becoming active. In such cases they stain deeply 

 and the nucleus possesses usually a number of nucleoli (Fig. 16, PI, 



I). _ _ — i 



After the endosperm tissue has been built up by the formation 

 of cell walls a number of large cells with greatly enlarged nuclei 

 become differentiated in the antipodal region (Fig. 21, PI. II and 

 Fig. 36, PI. III). It has been impossible to trace the origin of this 

 tissue directly by following the actual division of the original antip- 

 odal cells, yet there seems little doubt that it is derived in this 

 way. In many cases no sharp line of demarkation can be noted 

 between these cells and the endosperm tissue, still this does not 

 preclude the possibility of their being formed by division from the 

 antipodals. The enormous size of these cells and the greatly en- 

 larged nuclei, give them an entirely different appearance from the 

 normal endosperm cells (Fig. 21 and 23, PL II). Furthermore a 

 varying number of deeply staining bodies are found in the cytoplasm 

 outside the nucleus and these are lacking throughout the endosperm 

 tissue (Fig. 23, PI. II). This antipodal tissue is built up rather 

 later than the endosperm and in most cases seems to invade the 

 latter (Fig. 21, PI. II and Fig. 36, PI. III). 



The first stages in embryogeny were briefly described above (Fig. 

 14-15, PI. I). In the more or less cylindrical pro-embryo made up 

 of a row of three or four cells, anticlinal or longitudinal walls 

 first appear in the anterior cell. These divisions are followed by 

 further transverse and longitudinal ones with the result that the 

 pro-embryo becomes more or less club-shaped (Fig. 27, PI. II). In 



