meristems of Ferns as a Phylogenetic Study . 389 
DESCRIPTION OF FIGURES IN PLATES XX, 
XXI, XXII, XXIII, & XXIV. 
Illustrating Professor F. O. Bower’s paper on the Comparative Examination of the 
Meristems of Ferns as a Phylogenetic Study. 
ROOTS. 
Fig. 1. Scheme of construction of the apex of the root with a three-sided pyra- 
midal apical cell, quoted from Sachs’s Arbeiten, Bd. II, Taf. Ill, Fig. 12. 
Roots of Osmunda regalis , Figs. 2-4, and 6-1 1 (x 216). 
Fig. 2. Transverse section of apex of root with a three-sided initial, but the seg- 
ments not regular. 
Fig. 3. Ditto. Three initial cells ( x ) separated by principal walls p,p. The 
sextant walls are marked s, s. 
Fig. 4. Transverse section immediately below the root-cap, showing three 
initials ( x ) : the dotted line is a cell-division in the root-cap, seen on focussing 
deeply, and this shows that the section has passed through the initials, and is not 
below them. 
Fig. 5. Quoted from Naegeli and Leitgeb, Taf. XIV, Fig. 5, a transverse section 
of the apex of the root of Pteris hastata, as seen by focussing below the apical cell. 
p, p , the principal walls, s, s, the sextant walls. Compare this, which is an optical 
section through the segments below the initial, with Figs. 3, 4, which are sections 
through the initials of Osmunda. 
Fig. 6. Median longitudinal section, with pyramidal apical cell, tr, cells develop- 
ing as tracheides. 
Fig. 7. A very irregular meristem, with a pyramidal apical cell (x). Segments 
undergoing repeated periclinal division. 
Fig. 8. Two oblong initial cells ( x , x) : segments are cut off by periclinal walls 
from both ends of them, and by anticlinals from their sides. 
Fig. 9. Two similar initials with their segments. 
Fig. 10. Young lateral root with two oblong initials, xy , the xylem of the 
main root, p, the pericambium. 
Fig. 11. Apex of a young lateral root in longitudinal section. 
Roots of Todeabarbara , Figs. 12-16 ( X216). 
Fig. 12. A very regular meristem in transverse section, showing four initials ( x , x). 
Fig. 13. Apex of root in longitudinal section, showing two pyramidal initials. 
Fig. 14. Ditto, with two oblong initials. 
Fig. 15. Group of cells derived from one rhizogenic cell of the endodermis 
showing two oblong initials ( x , x). 
Fig. 16. Apex of a rather older lateral root with two pyramidal initials ( x , x). 
Fig. 17. Scheme of construction of a root of the Marattiaceous or coaxial type. 
A A, axis; aa } anticlinals; pp, periclinals ; xx, initial cells. 
D d 2 
