Mr Barber, Parasitic Trees in Southern India. 253 
collapsed cells in the cortex on either side of the nucleus (Plate II., 
fig. 1, the dotted lines). These bands form separation layers in 
that the cells on the two sides of each speedily acquire different 
characters as regards their arrangement and contents, the outer 
layers becoming early permanent and, later on, moribund. The 
collapsed layers extend, in the sandal, from the end of each 
cortical fold, towards the base of the haustorium as far as the 
point where the haustorium proper joins the transitional region 
(Plate III., fig. 7, cl). 
When entrance has been effected, a portion of the haustorium, 
the sucker, is thrust into the root attacked in the form of a 
tongue-like protrusion. This entering process remains simple in 
monocotyledon roots or in soft substances. But in dicotyledon 
roots with a firm woody cylinder, the sucker, unable to penetrate 
the denser lignified tissues, passes on either side along the line of 
the cambium, as two broad lobes or lamellae. The cambium is 
destroyed as the sucker lobes pass along it, and the formation of 
secondary wood in the host’s root ceases at the invaded portion. 
After entering, the sucker swells greatly in thickness and the 
bark and cortex of the attacked root are thrust back as cortical 
wings until they are more or less parallel (Plate III., fig. 7). 
Shortly after the sucker has reached the woody cylinder of the 
host, two broad parallel bands of vessels appear in it, separated by 
a parenchymatous “pith.” The ends of these bands apply them- 
selves, as isolated rows of vessels, to different parts of the xylem 
of the host. As these vascular elements are connected with those 
of the transitional region, continuity is thus attained between the 
vessels of host and parasite. Cambium is present on the outer 
edge of each band of vessels but phloem elements are not met 
with, the latter being only found in the mother root and the 
vascular branch from it in the transitional region. The course 
taken by the vascular strand in the haustorium is characteristic, 
and may be followed on fig. 7 of Plate III. Passing downwards 
from the mother root, the vessels, at first forming a compact strand, 
separate widely in the transitional region. Below this they ap- 
proach one another again, thus forming a wide loop, and pass to 
the two parallel bands of the haustorial axis already mentioned. 
At the point of junction of the transitional region and the hausto- 
rium proper, that is, just above the widest part of the loop, a 
curious change soon takes place in the vessels, in that they become 
disorganised, lose their markings and become filled with a yellowish 
mucilaginous mass. This point in the vascular system may be 
appropriately called the “ interrupted zone.” Secondary thicken- 
ing takes place to a moderate extent in sandal haustoria. 
Such is, in brief, the history of the development of the hausto- 
rium of Santalum album, and for fuller details the reader must be 
