1898] THE LEAF AND SPOROCARP OF PILULARIA 9 
by three more section walls. Wall IV is dorsal to the marginal 
cell and nearly parallel to wall III (fig. 78), wall V is on the 
ventral, and VI on the dorsal side of the marginal cell (figs. 78, 
zg), and the ultimate marginal cell is thus of the seventh grade, 
just as in the capsule of Marsilia (Johnson ’98). 
THE STALK. 
The type of primary division just given is the one found in 
most of the later segments of the sporocarp, but in those at the 
base, which form the stalk, wall IV is often followed immediately 
by a pericline in the marginal cell which ends its activity as such 
(jig.20). The further fate of the various sections and the mar- 
ginal cell is quite similar to that found in the leaf. Procambium, 
ground meristem and protoderm layers are formed in all; the 
latter gives rise to epidermis and hypodermis ( ¢ 9, 4 y, figs. 20, 
2r),and the ground meristem to the two or three-layered meso- 
phyll and to the partitions separating the small and irregular air 
canals. We find a notable difference in the fate of the procam- 
bium, for the eccentric vascular bundle of the stalk is developed 
entirely, or nearly so, from the procambium of section I (a 4, fig. 
20), while most of the procambium of the other divisions is 
devoted to the formation of the large stereome bundle which 
lies ventral to and partially surrounding the vascular bundle 
(s cl, figs. 22, 31-33). This fuses below with the central 
stereome of the stem, but ends abruptly above at the basal wall 
of the capsule. In the mature sporocarp the stalk is sharply 
curved in ventrally, is smaller at the lower end and considerably 
enlarged at the upper end where it joins the capsule, at which 
point also it is peculiarly modified on the dorsal side, as will be — 
described in detail in speaking of the wall of the capsule. 
The vascular bundle of the stalk, as Meunier has pointed out, 
does not fuse with that of the leaf in the way described by 
Goebel, but usually, according to my own observations, fuses 
first with the bundle of the axillary bud, and then this composite 
bundle reaches that of the stem at or near where the leaf bundle 
joins the latter. 
