1 3 2 Johnson . — Cbz the Development of the 
base of the capsule (b.w., Figs. 31 a, 42, 44). In the periblem 
above the dorsal bundle in these segments and in several 
of the older soral ones is developed a wall of thickened cells, 
enclosing between it and the dorsal hypodermal wall a lens- 
shaped mass of looser cells, the ‘ linsenformige Raum ’ of 
Russow (/. c., Fig. 44). There is an opening into this space 
just above where the dorsal bundle pierces the basal wall, 
and another at the anterior end, out of which there projects 
a rod of brown-walled cells (br., Fig. 44). The epidermal 
cells above this cavity swell out later to form the upper 
tooth of the capsule {it. /., Fig. 44). 
Each segment of the next eight or nine pairs give rise to 
a sorus. Section I in these segments develops much as in 
the segments of the stalk, as we have seen above. But the 
other sections have a peculiar history. Sections III, IV, and 
VI, dorsal to the marginal cell, widen rapidly at their outer 
ends, while sections II and V do not. The ultimate marginal 
cell is thus pushed around to a ventral position, the inter- 
polated section IV contributing largely to this end (Figs. 27, 
29 ; cf. Figs. 8, 9). Finally, all other cells in this region grow 
out beyond the cells formed from the basiscopic ultimate 
marginal cell, and grow together over the outer ends of them, 
completely enclosing them (Figs. 29-33). 
The Vascular Bundle-System. 
The dorsal bundle, arising from the plerome of section I in 
all the segments of the capsule, gives rise in each soral 
segment to a lateral branch that runs down back of each 
sorus, between this and the lateral wall of the capsule. At 
a point about opposite the middle of the sorus the lateral 
bundle splits to three branches, as Russow has shown. Two 
of these (/. b . Fig. 33) continue on in the course of the 
single part of the bundle, while the third turns abruptly 
inward to connect with the placental bundle of the sorus 
(/. br.> Figs. 33, 44). The dorsal and single portion of the 
lateral bundle arises from the basiscopic half of the plerome 
