oy 
ys? 
PINITES RUFFORDI, FROM THE ENGLISH WEALDEN FORMATION. 42] 
about 3 mm., and of the narrowest 1 mm.; between these 
extremes the breadth varies considerably. In some parts of 
the section one finds two rings of narrower tracheids separated 
by seven or eight wider tracheids, one of the rings being a 
typical annual zone of summer wood, and the other consisting 
of fewer narrow elements, and occasionally incomplete. Such 
appearances may probably be referred to local changes in 
growth or in the supply of nutrition, and, when the two zones 
of narrow tracheids are complete, we may regard them as an 
example of two rings of growth formed in one year. In 
fig. 1 a transverse section is somewhat diagrammatically repre- 
sented about three times the natural size. On the left-hand 
side of ring 1 (on the left-hand side of the figure), and 
Fia. 1. 
Transverse section of the wood of Pinites Ruffordi, showing annual rings, 
resin ducts, &e. (x3). 
Separated from it by six to ten tracheids, there is a second 
narrower zone of smaller tracheids; similarly, close to ring 2, 
@ second zone of narrower elements occurs; both these may be 
described as double rings. Instances of “double rings of 
growth” have been recorded by Kny, Strasburger * and other 
writers in recent trees. Another striking feature presented by 
a transverse section, is the abundance of resin ducts; on the 
right of ring 4 we find a row of numerous and crowded canals 
and on the right hand side of these, the diameter of the 
tracheids next to the duct is about the same as that of the 
summer tracheids. Again, in the summer wood of ring 6, 
there are a fairly large number of canals, also between rings 10 
* Strasburger, ‘ Histologische Beitrige,’ Heft iii. 1891, p. 25. 
