1902] ON THE DEVELOPMENT OF CERTAIN PIPERACEAE 327 



The Inner layer is made up of radially elongated, prismatic 



cells, the middle layer of periclinally expanded ones, and the 



outer of more or less cubical cells {^figs, 24, ^§, 27). 



The mature seed is distinctly triangular in transverse section, 



but the surface of the fruit may be five or six-angled from the 



pressure of adjacent fruits upon each other In the closely packed 

 spike. 



The definitive archesporial cell gives rise immediately to a 

 single megaspore, no indication of degenerating sister megas- 



pores being seen {jigs, ig, 20, 21), This single megaspore, 



after enlarging slightly, gives rise to two, four, and finally eight 

 nuclei in the typical manner {figs. 20,21, 2j), The large egg 

 and the two synergids, all with distinct cell-walls, occupy the 

 upper end of the elongated embryo sac. The polar nuclei fuse 

 to form a large endosperm-nucleus {figs. 2j, 2j), which may be 

 located near either the base, middle, or upper end of the embryo 

 sac. The antipodal nuclei collect at the extreme base of the sac 

 and do not develop cell walls until somewhat later than the egg 

 and synergids {figs. 2j, 25). 



At about the time of fusion of the polar nuclei the embryo 

 sac ceases to elongate and begins to broaden rapidly, so that the 

 mature embryo sac is nearly spherical in form {fig- ^i). At 

 this stage the egg and synergids are somewhat flattened against 

 the upper end of the embryo sac, and the very large antipodals 

 bulge into the cavity of the sac from below {figs. 24, 2j), 



As in the case of Piperjnedinm mentioned above, the synergids 

 and antipodals are long persistent {figs. 26, 2j), though appa- 

 rently not quite so long as in the latter genus. The number of 

 antipodals found below the endosperm mass in the nearly ripe 

 seed is frequently but three; sometimes, however, there may be 

 as many as six or eight {fig. 28), which probably arise by the 

 division of the three primary ones, after their cell walls are 

 formed. The prominence of the antipodals here suggests that 

 their function is an important one. They are placed at the base 

 of the embryo sac, in what is probably the direct line of food 

 transit to the sac, and perhaps play a part in the transmission or 

 possibly in the elaboration also of this food material, though the 



