Manchester Memoirs, Vol. xlv. (1901), No. K. 5 



stand out clearly and are of special interest. They lie 

 near the middle of the section and show a more definite 

 arrangement of cells than is shown by the rest of the 

 tissue. One of these groups is still further enlarged in 

 Fzg-. 4 (P/aU J I.) This group has a clear-cut oval out- 

 line, formed by a darker cell-wall surrounding a group 

 of six or seven cells. One can clearly distinguish a 

 central cell surrounded by five or six peripheral cells. 

 There seems to me little doubt that such a group of cells 

 corresponds to one of the large spaces usually met with 

 in the phloem region of this fossil, and this identification 

 is rendered all the more probable from Mr. Seward's 

 observation in Binney's slides of "The occurrence of a 

 few smaller elements enclosed by the thin membranes 

 which mark the outlines of the sacs." ^ These he figures 

 in Fig. 3 and they are also seen in the oblique section 

 of a leaf-trace in Fig. 5 on Plate HI. The very 

 definite oval outline of the group of cells before us in 

 Fig. 4 of the present communication would lead us to 

 suppose that it had arisen from the sub-division of a 

 single cell, in which a central and a number of peripheral 

 cells had been cut off, very much as the nodal cell of 

 Chara divides into a central and peripheral cells. Another 

 and perhaps a more useful comparison might be made 

 with the separation of a number of companion cells from 

 a central sieve tube. I have examined the sections 

 under consideration very carefully, to obtain, if 

 possible, earlier stages of division than that shown 

 in Figs. 3 and 4, and have been able to find a 

 number of phloem cells divided by delicate walls 

 into two, three, or more cells, but it was impossible to 

 decide definitely whether these stages were preparatory to 

 further division as illustrated in the special group referred 



1 Vide Seward, loc. cit. (I.), p. 147- 



