or CALAMITEAN STROBILUS. 265 



Fig. 3. Transverse section of part of central portion of fig. 2, made in the 

 line X X, fig. 13: c, c, primary peduncles ; d, d, longitudinal 

 canals of axis ; e, e, bundles of reticulated pleurenchyma ; /, /, 

 larger pyriform apertures in the bractigerous disk ; g, ff, smaller 

 apertures ; h, k, bases of the sporangiophores ; i, sporangia. 



Fig. 4. Slightly oblique transverse section of one of the upper segments of 

 the strobilus, made in the line w w oi fig. 13, passing through 

 the bractigerous disk opposite to x (fig. 4), and a little above it 

 in the rest of the section : a, medulla ; c, primary peduncles ; h, 

 h', h", sporangiophores ; i, sporangia ; I, cellular sporanginm- 

 walls, seen in section. 



Fig. 5. Central part of a transverse section of half of the segment figs, i 

 and 2, made in the plane y y oi fig. 1 3 : a, medulla ; c, c, ex- 

 ternal ridges of the central axis, identical with the primary pe- 

 duncles of fig. 4 ; i, sporangia. 



Fig. 6. Vertical section of segment figs, i and 2 : a, medulla ; c. central axis ; 

 h, sporangiophore ; i, i', sporangia ; k, bractigerous disk ; h', 

 bract. 



Fig. 7. Lateral half of a vertical section of one of the upper segments : a, 

 medulla ; c, cellular tissue descending from the node e towards 

 the bractigerous disk below ; c', prosenchyma ascending towards 

 the next bractigerous disk above; c", thin layer of prosenchyma 

 separating the larger pyriform canal / from one of the smaller 

 ones not seen in the section ; e, arches of reticulated pleurenchyma 

 forming the node ; e', the same pleurenchyma prolonged upwards, 

 external to the prosenchyma of the axis ; h, sporangiophore be- 

 longing to the bractigerous disk c ; i, i, spores ; I, inferior wall 

 of a sporangium resting upon the bractigerous disk c ; V, ex- 

 ternal wall of the sporangium i. 



Fig. 8. Two reticulated fibres from 7 e, more highly magnified. 



Fig. 9. Transverse section of upper part of a sporangiophore : h, peripheral 

 margin ; h\ inner margin. 



Fig. 10. Transverse section of part of a sporangium- wall : I, inner surface: 

 V, outer surface. 



Figs. II, 12. Detached spores: i, outer cell-membrane ; i', inner-cell mem- 

 brane. 



Fig. 13. Restored vertical section of five inferior segments of the strobilus : 

 a, medulla ; b, outer margin of bractigerous disk ; c, central 

 axis ; h, sporangiophores ; i, i, sporangia ; k, external bracts ; I, 

 sporangium-walls ; w w, plane of section, fig. z^; x x, plane of 

 section, fig. 3 ; y y, plane of section, fig. 5. 



