364 Jeffrey and Cole.— Experimental Investigations 
The fusion of pits observed in the foregoing figure is not here apparent, 
since it has already taken place in the lateral walls. 
It is clear from the observations recorded in the preceding paragraph 
that the vessels of Liriodendron are distinguished from the tracheides 
by their larger calibre, the numerous pits of the lateral walls, either opposite 
or fused to constitute scalariform pores, and finally by the scalariform 
perforations, bringing about open communication between vessel and vessel. 
These perforations are obviously the result of modification of the opposite 
rows of lateral pits or of the scalariform fusions of these. It thus becomes 
evident that the vessel in types like Liriodendron is not far removed from 
the tracheide in its organization, although it possesses the distinctive 
features of a vessel. In some instances the perforations may be absent, 
but the essentially vascular character of the element may then be inferred 
from the numerous opposite or fused (scalariform) pits of its lateral walls, as 
well as from its characteristically large calibre. There is an interesting 
resemblance between the vessels of Liriodendron , in fact, and those found in 
certain Ferns and other Vascular Cryptogams. In Pteris aquilina , for 
example, vessels take their origin from the disappearance of the borders 
and membranes of certain of the scalariform pits of the wall. It is impor- 
tant to note, however, that in Pteris and similar forms the scalariform 
pitting is a primitive feature of organization, while in the Dicotyledons 
it has been derived secondarily by the fusion of opposite rows of pits in the 
lateral walls of the vascular elements. 
The considerations put forward in the two preceding paragraphs bring 
us to the discussion of the scalariform elements found in proximity to the 
protoxylem in Driniys and in an indefinitely wider region in Trochodendron 
and Tetracentron. Those scalariform elements lying farther away from 
the primary region of the wood are of significance in the genus Drimys. 
Here one finds a marked tendency to scalariform pitting in the terminal 
regions of the tracheary elements, after it has been superseded in the rest 
of the walls by typical round bordered pits. In the case of Drimys we are 
left in doubt by reason of the proximity of the elements to the scalariform 
tracheides of the primary wood. In Trochodendron and Tetracentron , 
however, this ambiguity does not occur, since the vessel-like tracheides are 
found in regions far outside the primary wood and consequently cannot 
reasonably be interpreted as persistent scalariform elements of the first- 
formed wood. 
The conditions resulting from wounding in the case of Drimys , never- 
theless, seem to throw more light on the subject under discussion than 
is afforded by the study of the first annual ring, the leaf, and the root, 
all regions which we have been led as a consequence of the investigations 
on gymnospermous anatomy in recent years to regard as the seats of 
ancestral characters. By reason of the possibility of the confusion of 
