Cc. A. BARBER. 3)5 
This separating layer is constantly present and may be regarded 
as an outer collapsed layer. It is clearly seen in the figure under 
discussion (Plate X, fig. 1). Such outer collapsed layers are not 
infrequently found in Santalwm (cf. Santalum, Part II, para. 7) 
and those in Olax are, as in that case, probably due to the 
shrinkage of the outer cells of the cortex. We shall refer to 
these outer collapsed layers in dealing with the connection 
between haustorium and mother root. 
The deposition of crystals of calcium oxalate has been 
referred to on several occasions and has been regarded as evidence 
of a complete cessation of activity in the tissues bearing them. 
At first present only in the outer layers of cells under the corky 
surface, later on they appear in masses in the radiating cells. 
They are also frequently met with in the parenchymatous cells 
inside the vascular loop and in the little nest of cells opposite 
the ends of the cortical wings of the host, tissues clearly of no 
further use to the haustorium. Their occurrence in the clear 
zone is rare. Within the collapsed layers, that is, in the original 
nuclear area, they are also rarely found. In the few cases 
observed, they form, in this region, long strings of minute black 
crystals passing through a series of cells in a long line. 
The mother root from which the haustorium was developed 
is seen cut across on the right hand of the top of the section 
(Plate X, fig. 1). The space traversed by the vascular bundles 
uniting it to the haustorium has been termed the transitional 
region. The strands of vessels in the axis of the haustorium are 
continuous with similar elements right up into the mother root. 
They are thus accompanied by the cambium. But the vascular 
strand of the axis is devoid of bast. The phléem elements of 
the mother root are continued some way down, but cease in the 
transitional region. By observing their lower limit we shall have 
another means of judging the position of the line of separation 
between the haustorium proper and the region above it. The bast 
in Olax roots is distinguished asa layer of thin-walled cells densely 
filled with contents which are coloured light brown in spirit material. 
In this brown, undefined layer isolated groups of sclerotic cells 
