79 
inner cortex. The xylem of the elements formed from these second 
cambiums connects with the central xylem strands (which consist 
Fig. 5. 
Young root of Christmas Tree, 
a, xylem; b, phloem; c, cortex. 
of the primary and a certain amount of secondary wood) so that 
the protoxylems aie surrounded by later formed wood elements 
(Fig. 6). 
When this second ring of cambium patches has divided to a 
certain extent it ceases to divide and another new cambium is 
formed outside in the inner cortex. The bundles formed from this 
are not connected with the previous year’s bundles, but are separ- 
ated, as in the stem, by a layer of cortical tissue. All further 
growth in thickness after this is similar to that in the stem. The 
result of this method of growth is that the old root shares the 
stem’s characteristic of brittleness. Mucilage canals and inter- 
rupted medullary rays occur here as in the stem. 
PARASITISM. 
Nuytsia floribuncla is the sole representative of its genus. 
It is classified systematically with the Loranthaceae,* and on ac- 
count of this its autonomy lias long been questioned, though no 
definite evidence was brought forward. 
* See end of paper, p. 88. 
