732 
DR JOHN M'LEAN THOMPSON ON NEW STELAR FACTS, 
5. It is held that the sum of the ontogenetic evidence so far available for the 
Ferns shows that medullation, and the solenostelic and dictyostelic states arise in 
the ontogeny by intrastelar readjustment in which change of procambial destination 
is mainly operative. 
DESCRIPTION OF FIGURES IN TEXT. 
In these the general arrangement of stelar tissues is given in median longitudinal section, with leaf- 
and root-traces reduced to one plane. Leaf-traces and stelar gaps are lettered, and levels referred to 
are numbered. 
Fig. 1. Schizsea dichotoma, plan of stelar construction in an adult stem. Outer endodermis, En. ; phloem, 
cross-hatched ; xylem, black ; sclerenchyma, dotted ; parenchyma, white. There are endodermal pockets 
of varying depth, and isolated spindles of inner endodermis and wood in the sclerenchyma. 
Fig. 2. Schizsea dichotoma , plan of stelar construction in an adult stem. There is an isolated inner 
endodermal spindle in the thin-walled portion of the pith, and tracheides (T) are lodged in the bottom of 
an endodermal pocket. 
Fig. 3. Gleichenia pectinata, plan of stelar construction in a juvenile plant. 
Fig. 4. Lindsaya adiantifolia, plan of stelar construction at an adult node. 
Fig. 5. Lindsaya adiantifolia , plan of stelar construction in a juvenile plant. 
Figs. 6, 7. Loxsoma Gunninghamii , plan of stelar construction in two juvenile plants. 
Fig. 8. Loxsoma Cunninghamii, plan of stelar construction in the upper portion of a juvenile plant which 
has attained a solenostelic structure towards its. apex. 
Fig. 9. Acrostichum aureum, plan of stelar construction in a juvenile plant. 
DESCRIPTION OF FIGURES IN PLATES. 
Plates I-IY. 
. Figs. 1-6. Schizsea malaccana. Transverse sections of the stele of Schizsea malaccana, at successive 
levels in a juvenile plant. 1 is from the protostelic base with solid xylem-core ; 6 is from a level transitional 
to the adult stem, and shows the well-developed pith. A, xylem parenchyma ; B, endodermal bridge ; 
En., outer endodermis ; L, leaf-trace ; M, pith ; 0, parenchymatous gap in xylem ; Ph., phloem ; Pr., pericycle ; 
T, tracheides in the pith ; X, xylem. (All x 40.) 
Figs. 7-23. Schizsea dichotoma. 
Figs. 7-13. Transverse sections of the stele of adult specimen, reconstructed in text-fig. 1. The sections 
are from successive ascending levels referred to in the text ; En., inner endodermis ; G, xylic gap ; Pk., endo- 
dermal pocket ; S, sclerenchyma abutting on tracheides ; T, U, isolated tracheides ; W, base' of endodermal 
pocket ; Y, base of leaf-trace ; Z, parenchymatous part of pith. (All x 50.) 
Fig. 14. Transverse section of inner cortex of an adult plant. ( x 80.) 
Fig. 15. Transverse section of sclerenchyma of pith. ( x 80.) 
Figs. 16-18. Transverse sections of the stele of an adult plant, reconstructed in text-fig. 2. The sections 
are from successive descending levels referred to in the text ; En., inner endodermis : En/, En.", bases of 
endodermal pockets. (All x 50.) 
Figs. 19-22. Transverse sections of pocket En.", text-fig. 2, at successive descending levels until the 
pocket is closed. P, enclosed parenchyma; T, enclosed tracheides which form a spindle situated partly in 
the endodermal pocket and partly in the thin-walled selvage and continuous through the endodermis from 
the one to the other; T', adjacent tracheides in the selvage. (All x 80.) 
