452 Scott .— The Structure of Mesoxylon multirame. 
favourable as in the present case. On the other hand, the arrangement of 
the phloem elements in our plant is much less regular than that in Poroxylon 
(Bertrand and Renault, 1886 , p. 288), and the supposed resiniferous elements 
are a much more constant and conspicuous feature. 
The pericycle (about 1 mm. in average width, but varying considerably) 
is distinguished at once from the phloem by the irregular arrangement and 
larger size of the cells (PI. XII, Fig. 9). The matrix is formed of short-celled 
parenchyma, but embedded in this are very numerous and peculiar sacs, of 
large size, sometimes exceeding 200/x in diameter (Fig. 9), with brown or 
black contents. In some cases, but not very often, they resemble canals, 
having a layer or two of flattened cells around the cavity. Often the 
cavity appears divided into or filled by large cells. The longitudinal 
sections show that these sacs sometimes consist of a single row of elements, 
with more or less transverse walls and dark-brown contents. These are no 
doubt of the same nature as the ‘ resiniferous’ tubes of the phloem. In other 
cases the sacs, and especially the largest of them, appear irregularly parti¬ 
tioned up into short cells, much exceeding those of the parenchyma in size. It 
seems that the old sacs have been obliterated, perhaps by tylosis, though no 
clear evidence of such a process was obtained. The flattened cells surrounding 
some of the sacs, giving them a canal-like appearance, may be due to a local 
cambial activity around an effete organ, such as has often been observed in 
recent plants. The whole structure of these sacs suggests a state of senility. 
The periderm , formed at the outer border of the pericycle, has reached 
a thickness of fifteen or more elements. The cells, like those- of the peri¬ 
cycle from which they originated, are short. The zone is in places very 
irregular and may locally form two bands, the inner cutting deeply into the 
pericycle or even the phloem. 
As regards the cortex, it need only be said that numerous ‘ resiniferous 1 
sacs are present in the cellular tissue, and often extend into the bands of 
sclerenchyma. These sacs sometimes appear septate, but in other cases 
they are continuous for long distances, perhaps partaking of the nature of 
the fibres with which they are associated. 
From the description of this fine specimen it is evident that the plant 
must be referred to the species M. multirame , for it only differs from the 
type in quite minor characters. The specimen has been thought worthy of 
full consideration, as the excellent preservation exhibits in the clearest way 
the characters of the species and genus. 
A Possible Fructification . 
Of the remaining specimens referable to the species M ’. midtirame , the 
only one which requires special notice here is a small stem, 2 cm. in 
diameter, with the wood about 2 mm. thick. 1 It bore a number of axillary 
1 Sections 2563-2578 in my collection. 
