S axel by . — The Origin of the Roots in Lycopodium Set ago. 33 
EXPLANATION OF PLATE III. 
Illustrating Miss Saxelby’s paper on Lycopodium Selago. 
pi. = plerome, c. — cortex, i. = intermediate layer (probably endodermis), e . = endodermis, 
v. ~ protoxylem, ph. = phloem, x. — xylem group, st. — stele, of stem, r.pl. = plerome, 
r.pb. = periblem, r.d. = dermatogen, r.c. — cap, in. = inner cortex, in. — middle cortex, 
o. = outer cortex, of root, It. = leaf-trace, c.c. — concave, c.v. = convex, surface of bulbil. 
Fig. 1. Transverse section of stem, showing centre of origin of very young root, x 85. 
Fig. 2. Transverse section of stem, showing centre of origin of slightly older root ; protoxylem 
of stem ( v .) differentiated; base of leaf-trace (It.) also shown, x 85. 
Fig. 3. Transverse section of stem with still older root origin ; endodermis of stem with 
thickened inner and radial walls, x 85. 
Fig. 4. Transverse section near apex of stem bearing sporangia, showing base of root connected 
with phloem of stem, but not yet with xylem groups ; in. — mucilaginous remains of cells destroyed 
by root-cap. x 43. 
Fig. 5. Vertical section of young shoot grown from bulbil, showing young root origin ; 
dermatogen of root not yet divided to form root-cap. x 85. 
Fig. 6. Vertical section through apex of older root, showing origin of root-cap from dermatogen ; 
periblem two layers deep over apex. x 85. 
Fig. 7. Transverse section of obliquely growing stem, just above the level of the ground, 
showing roots all in one half of the stem cortex. This figure also shows the arrangement of the 
root-bundles with the convex side of the xylem towards the stem stele, the diarch type predominant. 
The section is cut from the part above the highest point at which a root appears outside the 
stem, x 22. y 
Fig. 8. Vertical section through bulbil and base of young shoot, from concave to convex side 
of bulbil, showing lateral origin of first root, and the same root cut transversely below the curve which 
has carried it into a terminal position. The section is cut in a direction almost parallel to the 
ground plane, though below the middle of the bulbil. The bulbil must therefore have been fixed 
on one side, and the root has described a double curve instead of growing straight down. x 2 2. 
Fig. 8#. Bulbil and shoot from which was cut the section figured in Fig. 8. Natural size. 
Figs. 9, 10, 11. Transverse sections of vascular bundles of roots in cortex of older stem. 
Figs. 9, 10, young roots with metaxylem still unlignified. Fig. 9, tetrarch root with additional 
protoxylem elements outside the metaxylem. Fig. 10, diarch root. Fig. 11, older root of triarch 
or intermediate type, x 369. 
Fig. 12. Transverse section of old root from cortex of stem, to show three cortical regions of 
root, x 85. 
D 
