35i 
Barber — Ciipressinoxylon vec tense. 
find a series of measurements in every recently described 
fossil, where the size of the specimen and the state of preserva- 
tion allowed of this. Yet I have only met with one instance 
in which such a series of observations has been made h 
The average diameter of the bordered pits in young roots 
and branches cannot be definitely stated. In the oldest 
parts of our sections it may be given as 13-14 /x 1 2 . 
Bordered pits on the tangential walls are present in all 
the sections, both radial and tangential (excepting in root 
(2), where the structure is not well preserved). According to 
Strasburger, tangential pits are found in the summer-elements 
of all Coniferous woods which do not possess 6 tracheidal 
elements * in the medullary rays 3 . The function of the latter 
is to supply a radial passage for the water, and the tan- 
gential pits accomplish this from one ring to another, there 
being no room in the last summer-elements for the radial 
pits. In support of this view Strasburger shows that tan- 
gential pits occur in other parts of the ring where the normal 
passage of water from one tracheide to another is interrupted, 
e.g. when a new medullary ray is formed, or opposite a resin- 
duct. A good example of this is seen among fossil woods 
in Pinites Ruff or di , where a solitary tangential pit is figured — 
opposite a resin-duct 4 . 
In Ciipressinoxylon , with its purely parenchymatous medul- 
lary rays, one would look for tangential pits in all the 
‘ species/ But they have only been recorded in six of the 
sixty species summarized by Beust 5 . A certain amount of 
perseverance is necessary to find the pits in some of our 
sections, although they are very well seen in the others. 
They are much smaller than the radial pits. 
1 Conwentz, 1 . c., p. 40. 
2 Kraus, Zur Diagn., gives 15 \x + as the usual size in Abietinae and Cupressinae, 
the elements of young parts being smaller. Schenk, in Zittel, states that the full 
size is generally reached during the first ten years. 
3 Strasburger, 1 . c., p. 9. 
4 Seward, 1 . c., Fig. 6. 
5 Beust, 1 . c. 
