116 Observations on the Vascular System of Ferns. 



connectile, and particularly in Osmunda cinjiamo^nea, 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 uncoiled 

 them, in every species of fern which I have examined, among 

 which are Aspidium marginale, A. acrostichoides, Asplenium 

 eheneum, Onoclea sensibilis, Adiantum pedatum, Pteris aqui- 

 lina, Osmu7ida cinnamomea, O. regalis, Polypodium connectile, 

 P. vulgare, Botrychiimi virginicicm, and others. From the draw- 

 ings given by Mohl, (Table xxxi, Fig. 1 to 3, ni 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 any 

 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 I have 

 found little to support this view, except the appearance of very 

 small ducts when so torn as to include only a single spiral Hue 

 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 Equisetu^n sylvaticimi, 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- 

 tect them, however, in E. hyemale, or in E. paliistre. 



I have not yet examined the Lycopodiacese in a young state. 



