84 
BOTANICAL GAZETTE 
[JANUARY 
on the oblique end wall, (3) the reduction in the border of these pits, 
(4) the disappearance of 
the tori and middle lamellae. 
In conservative regions of 
Ephedra’ all stages in these pro- 
cesses may be found; in other. 
words, there are all gradations 
between tracheids and vessels. 
Fig. 3 represents the radial view 
of the end of a vessel from the 
young wood of Ephedra mono- 
stachya. At the very end are 
@ 
D 
@ 
W 
Fic. 1 Fic. 2 
Fics. 1, 2.—Typical vessels from 
Ephedra monostachya: fig. 1, ape oe 2, 
tangential section; all figs. «25 
is not often seen, but various 
bordered pits and perforations 
are common in conservative 
regions. Fig. 4 represents a 
tangential view of a similar 
end wall and shows clearly the 
relationship between perfora- 
tions and bordered pits. For 
further details of the process 
the reader is referred to the pre- 
vious article by the writer (4). 
The typical vessel of Gne- 
ium, the highest of the Gnetales, 
differs from that of Ephedra in 
having a single large oval or 
elliptical perforation instead of 
several circular ones (fig. 5). 
It is, in other words, like the 
highest angiospermic type 
except that as a rule it exhibits a narrow border. 
typical bordered pits and higher 
up are seen stages in their trans- 
formation into perforations of 
the ordinary Ephedra kind. 
Such a gradual transformation 
intermediate conditions between 
> 
nS 
A) 
a 
% 
Fie. 3 Fic. 4 
Fics. 3, 4.—Vessels from Ephedra mono- 
stachya, showing relationship between per- 
forations and bordered pits. 
Even this 
* Young stem and root, node, seedling, etc. 
