CORRESPONDENCE. I41 
5. Describe the structure of nerve-cells and nerve-fibres, state 
what is meant by a motor, and what by a sensitive nerve, and 
distinguish between sensation and perception. 
6. Define reflex action, and give examples of actions of this 
nature. 
7. Describe the minute structure of cartilage, and give a 
general account of the way in which cartilage is converted into 
bone. 
8. What is the pulse, and how is it produced ? 
CORRESPONDENCE. 
<_<} —____. 
SOME FOSSIL PLANTS. 
(To the Editor N.Z, JOURNAL OF SCIENCE.) 
S1r,—Allow me to call the attention of geologists and others 
to a locality very rich in fossil plants, but as yet visited by compa- 
ratively few persons. The place was pointed out to me by Professor 
Black, who has known of it for some time, and with the kind help 
of Mr. Gardiner, of Pukerau, I was able to visit it, and get a good 
many specimens. The fossils occur in a bed of quartzite about 
five miles from the Pukerau railway station. A large landslip has 
laid bare the side of a hill for about a mile. The fossiliferous bed 
is very thin, perhaps only four feet in thickness where it is cut 
across by the slip, and is quite on the surtace of the ground. 
Beneath it there is a thick layer of brown sand, hardly firm enough 
to be called stone, and, as tar as I could see, destitute of fossils. 
Towards the east end of the landslip the stone is rich in fossil 
wood, and here there are very few prints of leaves; but the 
quantity of wood is astonishing. After the stone has hardened 
round the wood, the latter appears in many cases to have weathered 
out, leaving cavities in the stone. The large mass of stone lying 
on the face of the hill has, from this cause, the appearance of a huge 
sponge, so full is it of cavities. Towards the centre of theslip the 
stone is comparatively free from wood, and is very rich in leaves, 
and fruits, and small twigs. It would hence appear that the light 
leaves and twigs have been in some way sorted out from the 
heavier wood. The leaves and pieces of wood lie at all angles in 
the stone, and it seems likely that they were deposited under water 
and covered with sand. As no shells have yet been found in the 
stone, it is probable that deposition took place under fresh water. 
Decomposition of so much organic matter must have produced a 
great quantity of carbonic acid; and it is known that carbonic 
acid can decompose silicates. It is probable that the hardening 
of the sand into stone is due to soluble silica produced in this way. 
To the same cause may be ascribed the whiteness of the quartzite 
and its very high percentage ot silica. 
In less than two hours Mr. Gardiner and I obtained a sackful 
of specimens. The vegetation must have consisted mostly of 
