6o 
Hoar.-—A Comparison of the Stem 
This has in most instances the parenchyma transformed into substitute 
fibres. However, the above figure, which is one of several examples, shows 
clearly the parenchyma as being diffuse. In cases where the root of the 
same species was in question, a much greater quantity of diffuse parenchyma 
appeared. PL IV, Fig. 8, a transverse section of the root, and Fig. 9, a radial 
section of the same, show that that root was dead, and though the cause 
may have been natural or through wounding, in either case we have the 
parenchyma appearing according to the laws of reversion or retention. 
In Griselinia littoralis no well-formed parenchyma appeared. How¬ 
ever, there are a large number of cells filled with starch which were clearly 
substitute fibres. These are in a diffuse condition and clearly show that the 
plant at one time had diffuse parenchyma. 
I have shown no other figures of members of the Cornaceae since it is 
impossible to represent their condition well by a photograph. My speci¬ 
mens of Mastixia and of Helwingia unfortunately are very small and 
will not allow any far-reaching conclusions. However, in both instances 
diffuse parenchyma was found. I hope some time to be able to secure 
larger specimens, in order to study more thoroughly their structure. 
In the stem of Corokia , though it shows no well-formed parenchyma, 
yet the wood cells in certain regions show distinctly the clustered simple 
pitting so characteristic of the wood parenchyma cells. Often starch also 
shows in these. They are clearly substitute fibres showing the persis¬ 
tence of the parenchymatous characteristics. 
My material of Aucuba japonica unfortunately shows no case of wood 
parenchyma, whether or not it is because the stem and roots were small 
I cannot be sure. However, the rays are so abundant and so close together 
that there is scarcely room for, and no use for, parenchyma. Septate 
tracheides seem to be present to some extent, and many wood cells show 
nuclei. Here, also, spiral thickenings often appear upon the walls of the tra¬ 
cheides, a condition not at all common to the other members of the family. 
Turning now to the Araliaceae, I have been able to study genera 
including Aralia , Acanthopanax , Schefflera , Panax , and Hedera. In all 
cases where parenchyma appears it is clearly vasicentric. PI. IV, Fig. 10 
shows a transverse view of a species of Schefflera. It is hard to demonstrate 
parenchyma from this view. Yet if one looks in the vicinity of the vessels 
it will be seen that the cells here have thinner and darker walls than those 
of the general tracheary tissue. The two large vessels just below the centre 
of the figure show themselves to be nearly enclosed by small cells. Fig. 11 
shows a radial section of the same species. Here at each edge a vessel may 
be seen, and clustered over and about it are rows of parenchyma cells. In 
Fig. 12, which is also a view of the same species, but is tangential instead of 
radial, the parenchyma may be seen round the vessels. Here in the centre 
may be seen a number of septate tracheides. These may be easily told 
