368 Johnson : Development of Saururus cernuus L 



the tissue of the nucellus. The nucleus persists for a long time 

 but finally begins to show signs of degeneration and when the 

 seed is ripe there is no distinct nucleus to be seen. Darker 

 granules, which may be remnants of the nucleus, are sometimes 

 seen in the otherwise faintly staining contents of this lower en- 

 dosperm cell, or haustorium as it may perhaps prove to be in 



function (Fig. 6). 



The egg begins to develop when the neck contains a dozen or 

 more endosperm cells. The first division and several of the suc- 

 ceeding ones seem to be transverse. A suspensor a few cells in 

 length is thus formed (Fig. 6), and at the lower end the embryo 

 is developed. The latter in the ripe seed shows a pointed micro- 

 pylar or root end and two slightly projecting cotyledons below 

 with no distinct stem apex between them (Fig. 6). An axial 

 strand of procambium is just evident at this stage. 



The endosperm of the neck has by this time expanded laterally, 

 and uses up practically all of the nucellus above and at its sides. It 

 thus forms a double cone of tissue occupying the apex of the 



seed, with its lower point pushing in the upper wall of the lower 



endosperm cell (Fig. 6). The cells of this cap of endosperm are 

 thin-walled, have small nuclei and are filled with a granular darkly 

 staining substance, evidently cytoplasm. Several layers of the en- 

 dosperm cells nearest the embryo are devoid of stainable contents, 

 though their walls are still distinct, and none but those imme- 



* 



diately in contact with the embryo have their walls compressed 

 together. These empty cells are shown unshaded in Fig. 6. 



The fate of the synergids of the embryo-sac has not thus far 

 been determined. 



The stored food material is evidently contained chiefly in the 

 very abundant nucellar tissue or perisperm (psp, Fig. 6), which is 

 closely packed with starch. This tissue is developed by the rapid 

 growth of the basal part of the nucellus (Figs, i, 4, 6), which 

 finally fills nine tenths or more of the ripe seed, the cells being 

 arranged in rows radiating out from the lower endosperm cell 

 (Fig. 6). 



The carpel at this time forms a thick, warty coat of several or 

 many layers of outwardly rather loosely packed cells, the whole 

 evidently serving, by means of the enclosed air, to float the fruit in 



