248 
Boodle and Worsdell. — On the 
by Goeppert and Lecomte ; but we should also add that 
Sanio 1 describes the same thing. They may evidently be 
defined as the protoxylem elements of the branch which has 
united with the stem above, and they are pursuing, by a very 
oblique course, their way to the centre of the stem, there 
to unite with its protoxylem. These tracheides present 
a unique appearance, passing thus isolated through the paren- 
chyma for such a distance through the stem. The elements 
of the secondary wood of the branch pass off right and left of 
these tracheides to unite with the secondary wood of the 
central cylinder of the stem, while the large ray thus formed 
unites the pith of the two organs (Fig. 30). 
In the cortex of the stem of Casuarina , on its innermost 
side, next to the phloem, a longitudinal series of large stone- 
cells regularly occur ; they are oval or round in shape, and 
have very thick walls with simple pits running through them. 
Other cortical cells contain, like those of the medullary rays 
and parenchyma in the wood, crystals of calcium oxalate, 
which are usually single rhomboidal ones. In a young stem 
of C. stricta , Ait., a large part of the cortex was taken up by 
sclerenchyma fibres. 
Anatomy of Root. 
The structure of the young root is tetrach. This character 
very soon becomes difficult to make out, owing to the early 
appearance of secondary thickening, which produces a uniform 
structure of wood in this organ. In the older root the most 
striking feature is the large size of the medullary rays and the 
abundance of starch which they contain. The amount of 
woody tissue present is often reduced to a minimum, the 
greater part of the root being built up of parenchymatous 
tissue containing an immense store of large starch-grains. In 
the case of a root of C. tondosa , Ait., examined, the structure 
consisted of six triangular zones of tissue as seen in transverse 
section ; three of these zones consisted of woody tissue, and 
1 Loc. cit., p, 127. 
