252 
Boodle and WorsdelL — On the 
contents. They are identical in nature with those which are 
known to occur in Ephedra . 
The stems of G. Thoa and G. scandens which we examined 
were too young to show the anomalous secondary thickening 
described by De Bary 1 and Strasburger 2 , but the Sumatran 
species showed one anomalous zone of xylem and phloem. 
Apparently Gnetum has hitherto been described as possess- 
ing vessels with one perforation only, and Strasburger 3 men- 
tions this as one of the features which distinguish it from 
Ephedra. The vessels first formed by the cambium (in the 
internode) seem to have been overlooked ; they almost in- 
variably have several perforations. 
The anatomy of Ephedra is sufficiently well known ; but 
some of the points in which it differs from and agrees with 
Gnetum might be mentioned. 
One striking feature is the constant occurrence throughout 
the secondary wood of vessels, some with a double, some with 
a single row of perforations on their terminal wall. Besides 
vessels there are also corresponding tracheides. They differ 
from the vessels in having bordered pits instead of perfora- 
tions in their terminal walls, the former being just the same 
size as the last, and in there being usually one row of these 
instead of two, as in most of the vessels. But the most 
interesting part of this wood-structure consists of the transi- 
tional forms which are everywhere seen between tracheides 
and vessels. On some walls the central apertures were true 
perforations, while those towards the ends were bordered pits 
(Fig. 41). Some vessels were seen in which some of the 
perforations had still part of the border left round them, 
these having, often, on one side of them bordered pits, on the 
other thoroughgoing perforations. Indeed, almost all transitions 
are seen, where the border becomes narrower and narrower, 
till, finally, both pit-membrane and border disappear, and 
a true perforation is formed. Besides these elements there is 
the characteristic parenchyma of the wood, consisting of much 
Loc. cit., p. 603 (Fig. 233). 
3 Loc. cit., p. 144. 
1 
2 Loc. cit., p. 147. 
