286 Scott and Brebner , — On the Anatomy 
the interfascicular tissue, and not opposite a primary bundle 
at all, and after the first two rings are formed all regularity of 
arrangement ceases. 
We will now trace the development of a phloem-island 
(see Fig. 6). The first sign of its appearance is the increased 
activity of cell-division in a portion of the normal cambium. 
Otherwise the cambial divisions go on very slowly (at least in 
hot-house specimens), and wherever a number of fresh tan- 
gential cell-walls are apparent we may infer that an island is 
about to be formed. The cambium is at all stages of the 
development in contact with lignified cells on its inner side, so 
the formation of centrifugal phloem, as described by de Bary, 
is out of the question (Figs. 6 , 7, 8, 9, and 10). The develop- 
ment of the island is due to increased centripetal activity. 
There is not at first any corresponding diminution in the 
wood-forming productiveness of this portion of the cambium, 
and so the outer margin of the secondary wood may remain 
for a time unbroken. Thus the depressions (‘ anfractuosites ’) 
in the wood on which Herail 1 lays stress are not a necessary 
concomitant of the origination of the phloem-islands. They 
are in fact very misleading as a clue to the earliest stages, for 
irregularities in the outline of the wood are frequent, indepen- 
dently of the islands, and we have already seen that the con- 
verse is also the case. After a careful comparison of Herail’s 
Fig. 23 with our own preparations we cannot feel convinced 
that this figure really represents the origin of a phloem-island 
at all. The groups marked / are certainly primary phloem, 
which may or may not happen to lie opposite the place of 
development of an island, and which in any case take no part 
in its formation. The phloem of the islands is, as we shall see, 
the direct product of cambial divisions, and bears no resem- 
blance at any stage to the small-celled groups shown in 
Herail’s figure. His statement therefore that these groups 
‘become’ the phloem-islands cannot be accepted, though in 
other respects his account agrees with our observations. 
As additional phloem-elements are formed on the outside of 
1 1. c. p. 258. 
