304 Scott and Brebner . — On Strycknos. 
Fig. 7 . S. nux vomica , x 333, transverse section. More advanced stage. The 
phloem-cambium is now quite detached from the normal ring. The obliteration 
of peripheral elements is making progress. The island is now deeply sunk in the 
wood. 
Fig. 8. S. nux vomica , x 500. Longitudinal radial section of a phloem-island 
at a similar stage. The cells of the special phloem-cambium are shown with 
contents. Sieve-tubes and companion cells are shown. 
Fig. 9. S. nux vomica ,X333- Transverse section at a later stage. The 
phloem-island is now overtopped by xylem on either side, and divisions in the 
bast-parenchyma have completed the normal cambial ring outside the island. 
The phloem-cambium is in full activity, and the continuity of the radial rows of 
phloem-cells with .those of the internal xylem is especially evident here. 
Fig. 10. S. nux vomica, X333. Slightly later stage. The wood is now 
beginning to close in on the outside of the phloem-island. The number of 
obliterated peripheral elements in the latter has increased, but the cambium is 
still as active as ever. 
Fig. 11. S. nux vomica, x 333. Very old phloem-island, completely immersed in 
wood. An immense mass of obliterated elements is seen on the outside. The 
cambium shows but little signs of activity. This corresponds to Fig. 5 of the 
medullary phloem. 
Fig. 12. S. spinosa, x 333. Transverse section of root, in which secondary 
thickening has begun. A medullary phloem-group is seen in the pith opposite a 
group of primary xylem. These groups increase slightly by an external cambium 
as in the stem. Thickness of root about 4 mm. 
Note. — Figs. 4, 5, 6, 7, 9, 10, 11, and 12 were drawn under a power of 500 
diam. and subsequently reduced to two-thirds. 
