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1 



1902] ON THE DEVELOPMENT OF CERTAIN PIPERACEAE 331 



at this time made up of two hundred and fifty cells or more {^fig> 

 Jj). The endosperm cells divide actively, chiefly by anticlines, 

 I swelling meanwhile to encroach upon the perisperm, and upon 



reaching a diameter of 0.3°*"^ begin to burst the integument 

 near the micropylar end, but remain as a complete sac about 



the embryo [Jig'- 34)- 



As germination continues the embryo elongates, the two 

 cotyledons form below, and the primary vascular strand of the 

 hypocotjd appears ifig^Jj)- -The endosperm uses up the con- 

 tents of the surrounding perisperm cells, crushing in their walls 

 at first, and then pushes out above between the rent edges of 

 the integument and carpel {fig^ 35)- I^ so doing it either 

 pushes aside or carries up with it the persistent group of tapetal 

 cells and the overlying stigmatic regions of the carpel. The 

 embryo remains enclosed within the endosperm sac until it is 05""^ 

 long or more, at which time the cotyledons are 0.15"^"* or 0.2""^ 

 long, and have each a rudimentary vascular bundle connecting 

 with that of the hypocotyl. 



Soon after this size is reached the rapid elongation of the 

 embryo pushes at first the tip and then the whole of the radicle 

 through the upper part of the sac of endosperm (fig-J^^)- Still 

 later by the elongation of the cotyledons all but the tips of the 

 latter are pushed out of the endosperm [Jig. J?)- A swelling 

 of the- radicle, somewhat below the middle, first indicates the 

 limits of root and hypocotyl. Below this root hairs soon appear 

 abundantly, and later secondary lateral roots {Jigs^ J7, Jq)- 

 Above on the hypocotjd and cotyledons, even while the latter 

 are still enclosed by the endosperm, numerous glandular hairs 

 and many stomata are formed [figs. JJ, 38), Within the coty- 

 ledons between the vascular bundle and the upper surface of the 

 leaf there is found at this stage a single layer of cells with 

 darkly staining contents whose exact nature and function are as 



yet undetermined {Jig- 38). 



As the root of the seedling elongates it curves downward to 

 enter and anchor itself in the substratum by numerous root hairs 

 and secondary roots. Then the hypocotyl elongates and thus 

 raises the cotyledons with the adhering endosperm in the air 



