the Anatomy of the Genus Selaginella. 465 
EXPLANATION OF FIGURES IN PLATES XX 
AND XXL 
Illustrating Professor Harvey-Gibson’s paper on the Anatomy of 
the genus Selaginella. 
PLATE XX. 
Fig. 1. Origin of the vascular cords of the roots of Selaginella atroviridis , Spr. 
x 2. a. lateral branch ; b. dorsal abortive root ; c. main stem ; d. ventral root. 
Fig. 2. Root-system of S. atroviridis. Nat. size. 
Fig. 3. Transverse section of the root of S. atroviridis just previous to the third 
forking, x 350. Lettering as in Fig. 4. 
Fig. 4. Transverse section of the aerial part of the root of S. atroviridis. x 350. 
a. endodermis ; b. pericycle ; c. sieve-tubes ; d. phloem-parenchyma ; e. metaxylem 
(see Fig. 3). 
Fig. 5. Transverse section of the cortex of .S’. involvens, Spr. x 350. a endo- 
dermis ; b. cortex ; c. hypodermis ; d. piliferous layer. 
Fig. 6. Transverse section of the root of S. oregana , Eat., showing piliferous 
layer and hypodermis, sclerotic outer and thin-walled inner cortical cells, endo- 
dermis and monarch vascular cylinder. x 350. 
Fig. 7. Portion of the axis of S. Galeottei , Spr., showing the alternate origin of 
roots to right and left. Nat. size. 
Fig. 8. Vascular cords of S. Galeottei. Nat. size. a. vascular cords of the 
lateral branch ; b. of the root ; c . of the main axis. The arrow points towards the 
apex of the stem. 
Fig. 9. Root-system of S. caulescens, Spr. Nat. size. 
Fig. 10. Successive positions taken by the protoxylems at the bifurcation of the 
root of S. molliceps , Spr. Diagr. 
Fig. 11. Origin of the roots in S. Lobbii , Moore. Nat. size. a. adventitious 
shoot in the position of the dorsal root ; b. root arising from the adventitious 
shoot ; d and c. right and left branches of the shoot axis. 
Fig. 12. Transverse section of the root of S. Vogelii , Spr. x 350. 
Fig. 13. Root-system of .S'. Vogelii. Nat. size. 
Fig. 14. Transverse section of the root of .S', grandis , Moore, taken just before 
the forking, x 350. 
Fig. 15. Origin of the normal root of S. Lobbii. Nat. size. 
Fig. 16. Transverse section of the root (aerial) of S. Lobbii at the point of 
forking. The metaxylem has divided but not the protoxylem. x 350. 
Fig. 17. Transverse section of the aerial part of the root of S. Kraussiana , 
A. Br. x 550. a. metaxylem ; phloem-parenchyma ; c. sieve-tubes ; d. peri- 
cycle ; e. endodermis ; f. protoxylem. 
Fig. 18. Origin of the root in S. Wallichii , Spr., in transverse and longitudinal 
view. Diagr. 
Fig. 19. Centroxylic condition of one of the marginal bundles of the stele of the 
shoot at the origin of a root of S. helvetica. x 350. 
Fig. 20. Transverse section of one of the smaller roots of S. Wildenowii, Baker, 
x 550. 
