30 
OIIGANOGKAPHY. 
BOOK I. 
Link contends, that the fibre, although simple at first, soon 
forks and forks again, and that the branches thus produced 
all follow the direction of the spire. 
The termination of spiral vessels is, beyond all doubt, 
conical. This was stated by Nees von Essenbeck, in his 
Handhucli der Botanik^ published in 1820 ; and in 1824 
Dutrochet asserted, that they end in conical spires, the point 
of which becomes very acute ; but one would not suppose, 
judging from the figure given by the latter writer, that he 
had seen the terminations very clearly. If the point of a 
spiral vessel in the Hyacinth (Plate II. fig. 9.) be examined, 
it will be seen that the end of the spiral fibre lies just within 
the acute point of the vessel, and that the spires become 
gradually more and more relaxed as they approach the ex- 
tremity, as if their power of extension gradually diminished, 
and the membrane acquired its pointed figure by the diminu- 
tion of elasticity and extensibility in the fibre. It is not, 
however, always in a distinct membrane that the spiral vessel 
ends. In Nepenthes the fibres terminate in a blunt cone, in 
which no membrane is discoverable. (Plate II. fig. 11.)'*' 
A spiral vessel is formed by the convolutions either of a 
single spire, or of many, always turning in the same 
direction. In the first case it is called simple, in the latter 
compound. The simple is the most common. (Plate II. 
fig. 9.) Kieser finds from two to nine fibres in the Ba- 
nana. De la Chesnaye as many as twenty-two in the same 
plant. There are four in Nepenthes (Plate II. fig. 11.), 
five in Liparis pendula. In general, compound spiral 
vessels are thought to be almost confined to Endogenous 
* A singular change occurs in the appearance of the spiral vessels of 
Nepenthes, after long maceration in dilute nitric acid, or caustic potash : 
the extremities cease to be conical and spirally fibrous, but become little 
transparent oblong sacs, in which the spires of the fibres gradually lose 
themselves. This alteration, which is a very likely cause of deception, is 
perhaps owing to the extremities of the vessels being more soluble than 
the other part, the sac being composed of the confluent dissolved fibres. 
This is in some measure confirmed by the subsequent disappearance of 
all trace of fibres in any part of the vessels, under the influence of 
those powerful solvents. 
