BOT.-VOL. I.] CAMPBELL— NAIAS AND ZANNICHELLIA. 19 



The first integument becomes evident about the same 

 time that the primary archesporial cell undergoes its first 

 division. The basal part of the ovule enlarges and the 

 integument appears in the form of a ring, in the ordinary 

 way, and grows up about the upper part of the ovule, which 

 becomes the nucellus (figs. 35, 36) . The growth is stronger 

 on one side, almost from the first, the nucellus begins 

 to bend over, and the anatropous position of the mature 

 ovule is thus indicated. The first integument, like the cor- 

 responding structure in the stamen, is two cells thick and 

 closely resembles it in nearly every particular. It closes 

 over the top of the ovule, leaving, however, the narrow 

 micropyle open. The second integument, as usual, is 

 developed just below the first one (figs. 38, 39) , but is almost 

 entirely suppressed on the side in contact with the funiculus 

 (fig. 47). Even up to a late period the second integument 

 remains behind the inner one, but finally extends to about 

 the same level. 



The funiculus has an axial vascular bundle which devel- 

 ops a single line of tracheids with spiral or annular thick- 

 enings, which, like those in other parts of the plant, are 

 ultimately almost completely obHterated. From its basal 

 part, close to the micropyle, a bunch of short secretory 

 cells is found, probably concerned with the directing of 

 the pollen-tube into the micropyle. 



The further development of the archesporium shows con- 

 siderable variation, but corresponds in its essential details 

 with the typical form in most other Angiosperms. The pri- 

 mary archesporial cell very early divides by a transverse 

 wall into an outer tapetal cell, and a larger inner one (fig. 

 36), and the former next divides into two by a second trans- 

 verse wall (fig. 35). Usually the tapetal cell undergoes no 

 further development, at least until a much later period. In 

 one exceptional case observed (fig. 38), where the arche- 

 sporium was divided into five cells, it was not possible to 

 determine positively whether the third and fourth cells, which 

 were obviously sister cells, had been derived from the divi- 

 sion of the tapetum or from the inner of the two primary 



