BOT.— Vol. I.] CAMPBELL— SPAKG A NIUM. 3II 



is unusually large, transverse or oblique divisions may 

 also occur (fig. 39). A transverse section of the second 

 segment at this stage shows eight peripheral cells surround- 

 ing four central ones. 



In the upper segment, the next divisions are transverse, 

 and sometimes this gives the appearance of a complete 

 transverse division across, and it is possible that the seg- 

 ment numbered II by Hegelmaier may in some of his figures 

 really refer to a secondary transverse division in the termi- 

 nal segment. The separation of the epidermis is brought 

 about as in the second segment, and soon after another 

 series of similar divisions separates the central group of 

 plerome cells from the periblem. The plerome extends to 

 the basal wall where it ends abruptly, not being found at all 

 in the two lower segments. In cross-section (fig. 44, c) the 

 young plerome shows four cells, one belonging to each 

 quadrant, but there are soon found other longitudinal walls 

 which increase the number of plerome cells. 



The older embryo is not perfectly cylindrical in form, 

 but is somewhat broader in the plane of the future cotyle- 

 don. Sections made in this direction have the upper seg- 

 ment nearly circular in outline, but the median wall is often 

 somewhat oblique, so that the segment is not always per- 

 fectly symmetrical. In this view the small basal segment 

 usually shows a vertical division into two nearly equal cells. 

 In the cotyledon, which constitutes the major part of the 

 terminal segment, the epidermis is already clearly differen- 

 tiated, but this is not always so evident in the second seg- 

 ment, where the interlayer of cells usually undergoes 

 another periclinal division, which is never the case, so far 

 as I could determine, in the epidermis of the cotyledon. If 

 the section is made at right angles to the face of the coty- 

 ledon (fig. 42) the embryo appears more pear-shaped in 

 outline, and the basal segment may appear undivided. 

 Cross-sections of similar embryos show that in such cases 

 the basal segment is composed of but two or three cells. 

 In a number of instances the second transverse wall was 

 very oblique (fig. 42) and might even intersect the ba'sal 



