298 Scott and Brebner. — On the Anatomy 
regions. Divisions then take place in the cells of the pericycle 
outside the phloem-masses, and thus the normal cambium 
again forms a regular ring. The process is now repeated. 
Abundant wood is again formed opposite the primary bundles, 
while between them a smaller amount of wood and excessive 
bast is produced, until the cambium closes in a second time. 
This goes on indefinitely, and so the wood ultimately consists 
of alternating radial portions quite different in structure. The 
portions lying opposite the primary xylem-groups consist of 
normal wood, while the interfascicular regions are made up of 
successive tangential plates of non-vascular wood and of soft 
bast. There are four radial masses of each kind in Thunbergia . 
The process only differs from that in Sirychnos in the facts 
that in the latter the xylem is of similar structure through- 
out, and that the phloem-islands do not all lie in the same 
radial lines. 
In Goodenia ovata Vesque 1 found that there is a normal 
ring of bundles, but as regards five of these the cambium is 
extrafascicular, the phloem of these bundles thus becoming 
buried in the wood. This is a case of what may be termed 
primary phloem-islands. It is not mentioned by Solereder 
under this head, as it obviously does not fall under his defini- 
tion of interxylary phloem, but from our point of view this 
case affords an interesting parallel to the process in Strychnos 
and the Acanthaceae. 
Lastly we may mention the phloem-groups in the xylem of 
the root of certain Onagraceae, Solanaceae, and Gentianeae 
described by Weiss 2 . These growths are formed directly from 
the cambium on its inner side. They never grow subsequently 
by means of a special cambium of their own, and thus differ 
from the similar groups in the root of Salvadora , and from 
the interxylary bundles in the roots of Cruciferae and Cucur- 
bitaceae. 
These last-mentioned bundles are formed sometimes in the 
parenchymatous part of the secondary wood at a distance from 
1 1. c. p. 146. 
2 Flora, Bd. lxiii, and Bot. Centralblatt, Bd. xv, p. 407. 
