87 
The haustoriogens are formed along the whole length of the 
underground stems and this accounts for their long life in the 
soil when the aerial parts have been removed. They can obtain 
all the organic and inorganic food materials they need without 
assistance of aerial shoots. Sometimes this underground stem can 
be traced along by the line of dead, dying, and weakened plants. 
In other cases the attack seems to cause the host plants very little 
inconvenience. The number of the roots affected is, of course, the 
deciding factor as to whether the plant will suffer or not. Some- 
times nearly every root is surrounded by the haustoriogens of 
Xuytsia. At Como this is the ease with banksias, ti-trees (Mela- 
leuca viminea), and numerous other plants, both shrubs and 
herbs, many of which have been killed. 
Fig. 11. 
Carrots attacked by the haustoriogen of 
Nuytsia. 
A, appearance of attacked carrot. 
B, vertical section of same showing ligature 
effect of haustoriogen. li, the haustorio- 
gen. 
The rapidity of growth of the haustoriogen was shown in the 
case of the attack on some carrots at Como. These when only 
half-grown started to die off and on digging down it was found 
that the roots were surrounded by well-developed haustoriogens 
over half an inch in diameter (Fig. 11). The rapidity of develop- 
