116 Observations on the Vascular System of Ferns. 
connectile, and particularly in Osmunda cinnamomea, that if the 
petiole of the frond be snapped across and gently separated, hun- 
dreds of uncoiled ducts will be seen to connect the two fragments, 
as in Fig. 5, Plate I. These may often be drawn out to the 
length of two or three inches-without breaking. When broken, 
they exhibit the curious peristaltic motion which has been: noti- 
ced by Malpighi and others in true spiral vessels. This is evi- 
dently a mechanical effect, caused by the elongated and untwist- 
ed coil resuming its twisted state. 
I have found the vessels above described, and have unbédlels 
them, in every species of fern which I have examined, among 
which are Aspidiwm marginale, A. acrostichoides, Asplenium 
ebeneum, Onoclea sensibilis, Adiantum pedatum, Pteris aqut- 
lina, Osmunda cinnamomea, O. regalis, Polypodium connectile, 
P. vulgare, Botrychiwn virginicum, and others. From the draw- 
ings given by Mohl, (Table xxx, Fig. 1 to 3, m m, Table xxxv, 
Fig. 1,) it is evident, that the structure of the vessels in the ar- 
borescent ferns is similar, although it does not appear that a 
attempts have been made to uncoil them. 
In all the ferns which I have examined, I have sought in vain 
for any thing approaching more nearly to true spiral vessels than 
the lacerated ducts above described. 
As these ducts have precisely the structure which would re- 
sult from a compound spiral vessel, in which the spiral threads 
should be broken into short bars, I have carefully examined many 
young ferns, to determine if in the young state the bars may not 
be continuous, and thus form a true spiral vessel. But Ihave — 
found little to support this view, except the appearance of very 
small ducts when so torn as to iackade only a single spiral line 
of bars, in which case it is often impossible to see whether the 
bars are connected or not. 
I hence infer, that spiral vessels do not exist in ferns, and that 
the ducts when torn spirally have been mistaken for them. 
In connection with the above observations, I examined the 
young stem of E’'quisetum sylvaticum, in which I distinctly and 
repeatedly found small vessels which could be uncoiled spirally, 
and which presented no appearance of the bars seen in ferns, but 
which certainly appeared to be true spiral vessels. I did not de- 
a ‘si in EB. Lage or in £. palustre. 
yet examine Lycopodiacez in a young state. 
