38 STUDIES IN ROOT-PARASITISM. 
they touched one another. In others considerable resistance was 
offered by the root attacked. The sucker was carefully cut off in 
the usual manner and fresh growths took place in the cortical 
wings, by which the sucker as a whole was squeezed, the host 
acting as if engaged in occluding a wound (Santalum, Part II, 
Plate XVI). 
In self-attached haustoria in Olaa fusion of the tissues is the 
rule (Plate XI, figs. 1, 2 and 6). This is not however all, for the 
difference between such and ordinary haustoria is much greater 
than in Santalum. All the vascular tissues of the mother root 
are continued down the entire length of the haustorium and, at 
the end, are in connection with the similar tissues of the host’s 
root. 
We saw in paragraph 15 that the vessels of the axial strand 
of the Olax haustorium are uniform and narrow. In self-attached 
haustoria wider elements make their appearance, giving the 
whole strand an entirely different appearance (Plate XI, figs. 
1,3 and 6; Plate XII, figs. 2, 2a and 2a.) These wider vessels 
are identical in structure with the broader vessels of the secondary 
wood in Olax roots. Bast also is formed throughout the haus- 
torium (Plate XI, fig. 1, and Plate XII, fig. 2). Not only are the 
fibro-crystal bodies found all along the outer edge of the cambium 
in the axis, but well marked sieve-tubes with callus-plates are 
readily distinguishable, and staining with water-blue shows that 
they are present in very large numbers (Plate XI, figs. 3 and 4). 
From an inspection of this Plate, where these facts are illustrated, 
it is evident that a thorough fusion of host and parasite has taken 
place and that the cambium passes from one to the other so as to 
place the wood and bast in organic connection (fig 6), the 
formation of wood and bast in the haustorium keeping pace with 
that formed in the woody cylinder of the host (fig. 1). This has 
not been observed elsewhere in Olax or Sandal haustoria, but the 
description of Buckleya by Kusano indicates that in older 
haustoria the wood formation keeps pace with that of the host. 
Another point of interest is that, in self-attached haustoria, the 
vessels at the end of the sucker lobes before secondary thickening 
