1902] ON THE DEVELOPMENT OF CERTAIN PIPERACEAE 323 



becomes much longer than the inner and closes together above 

 the latter {^figs. 5, d). The inner integument a little later 

 becomes much thicker than the outer, of three layers except near 

 the micropylar end, and finally forms the principal seed-coat 

 {^figs. 6y II, 12, ij, i^.t'tn). One or two layers of cells of the 

 outer integument are recognizable in the ripe seed. The inner 

 walls of the inner layer are thickened with a granular deposit 

 resembling that found in the inner layer of carpellary cells in 

 Peperomia. The primary hypodermal archesporial cell divides 

 before the integuments have developed far, to form a tapetal 

 ceil above and the definitive archesporial cell below {Jig- 4, tp, 

 es). The tapetal cell later divides further to form four or five 

 la^'ers of cells abov^e the embryo sac in the ripe seed (Jigs. S, 12, 

 ^J» ip)y not how^ever, forming so sharply marked a group of cells 

 as in Peperomia pellucida (Johnson, igoo^, p. 2). The single 

 definitive archesporial cell becomes a megaspore directly, with- 

 out further division. It increases greatly in size, as does its 

 nucleus also {fig- 6, es) , but in so doing does not encroach upon 

 the cells above it in the nucellus in such a way as to indicate 

 that these are anything other than tapetal cells [figs. 6, 7, 5*, p, eSj 

 tp) , No evidence was discovered at any stage of the formation 

 of sister megaspores destined to final absorption by the func- 

 tional one, as in so many Angiosperms. 



The division of the megaspore occurs soon after the inner 

 integument has closed in to form a narrow micropyle above the 

 nucellus. This division occurs in the manner so frequently 

 described. Of the first two nuclei formed one goes to each pole 

 and there each divides [Jig. 7). The four nuclei thus formed 

 are frequently found grouped rather closely in the middle of the 

 embryo sac [Jig. 8)^ or in other cases we find a pair near each 

 pole. The eight nuclei formed at the next division soon group 

 themselves in the typical manner to form the ripe embryo sac 

 {fig- P)' The exact derivation of the polar nuclei has not been 

 made out with absolute certainty, but there seems no reason to 

 doubt from the condition shown in Jig. g that it is as commonly 

 found in the Angiosperms. 



In the ripe embryo sac the large ^%^ and the two smaller per- 



