1090 
Thompson . — The Anatomy and 
on the right is charged with a black resinous mass which has penetrated 
through the pits into the lumen of the vessel, where it remains as little 
globules. The deep colour of this material emphasizes sharply the doubly 
bordered character of the pits as well as the fact that the border on the 
vessel side is wider than that on the side of the parenchyma cell. 
A peculiar fact in connexion with these wood parenchyma cells is that 
they are often multinucleate. Fig. 23 shows a parenchyma cell in the wood 
of E. monostachya which in the short extent shown in the photograph 
obviously contains two nuclei. This condition obtains quite frequently, 
although it is often hard to demonstrate. Three and four nuclei have been 
observed in a single parenchyma cell. It would seem that the distance from 
the centre to the ends of such an extremely long living cell is too great to 
enable the single nucleus to perform its proper functions. Accordingly the 
original nucleus divides and the daughter nuclei become scattered along the 
cell. In fact, in the proper material it is possible to observe that the nucleus 
is actually undergoing division. Such a case is photographed in Fig. 24. 
The details of nuclear divisions were impossible to distinguish. 
In a few cases, as Strasburger 1 has pointed out, the parenchyma cells 
are further distinguished from tracheides by the presence of cross- walls such 
as exist in the parenchyma of most other woods. Such a wall is shown in 
PI. XCVI, Fig. 25, at the centre of the field. The inclination is typical. 
As a rule, however, septa are rare, and in some species were never seen. 
They are most abundant in E. monostachya. In no case was more than one 
septum seen in a single parenchyma cell, a condition which is in sharp 
contrast to that of the parenchyma of most woods. 
The typical wood-parenchyma cell of Ephedra is then, except for its 
pitting, merely a tracheide which has retained its protoplasmic contents. 
And in some cases we have seen that even its pitting resembles that of 
a tracheide. From these facts, and also from the entire absence of wood 
parenchyma in the ancient Gymnosperms, it may be concluded that the 
wood parenchyma of Ephedra has been derived from tracheides. Each 
parenchyma cell would therefore represent a modified tracheide. 
It is to be noted that this type of parenchyma differs essentially from 
that of the Conifers. The latter consists of short cells, a number of which 
together give the shape and size of a tracheide. In fact, Bailey 1 has 
recently brought forward evidence to show that this type was also derived 
from tracheides. The real difference then consists in the presence of numerous 
septations in the Coniferous cells. We have seen that in Ephedra a single 
septum is sometimes present, so that the distinction is not really so profound. 
The Conifers appear to have carried the process of septation much further. 
The cells which resemble them most closely, however, are to be found 
in the Angiosperms, where they have been called fibrous cells or substitute 
1 loc. cit. 
