157 



XXI. — On the Nature of Vessels possessing Longitudinal as well as 

 Spiral Fibres, found in certain Plants. By Edwin J. Quekett, 

 Esq., F.L.S., &c. 



Read May 17, 1843. 



Having given to the Society at some of its earlier meetings a few 

 observations on the structure and development of the vascular tissue 

 of plants, and as this subject still continues to occupy my attention, 

 I intend this evening to offer to your notice some remarks connect- 

 ed with vessels, which present an evident longitudinal, as well as a 

 spiral, arrangement of fibres in their interior. 



These vessels are not present in the majority of plants, and have 

 not, until within the last few years, been described ; but since they 

 have been detected, observers have found them in very different orders 

 of plants, and it is not improbable that future investigators may suc- 

 ceed in discovering them in a still greater number of plants than 

 those in which they have hitherto been observed. 



Schultz, in his ' Memoir on the Circulation in the Ducts of the 

 Latex,' figures a vessel of this kind found by him in Urania speciosa. 

 Previous to seeing this figure, I had found a vessel of the same struc- 

 ture in the petiole of the leaf of a Loasa. Mr. W. Wilson, of War- 

 rington, pointed them out to me in Typha laiifolia ; subsequently, I 

 have met with them in Canna bicolor. Mr. H assail has informed 

 the Society this season, that he had met with similar vessels in a 

 plant belonging to the Cucurbitacea ; and I have lately detected 

 something analogous in the footstalks of the leaves of the garden 

 rhubarb. 



The fact of finding vessels possessing a similar nature in classes 

 and orders of plants differing in many points in their structure, offers 

 the expectation, that hereafter they will be frequently detected in the 

 vascular system of a variety of plants, especially of those that exhibit 

 dots on the vessels arranged in some regular order. 



The usual characters that these vessels exhibit, are the following : — 

 In Exogens they do not appear to have either the length or diameter 

 of those found in Endogens, where they certainly constitute the largest 

 and longest of the vessels. 



In Loasa aurantiaca they do not exceed the -5-^uth of an inch, 

 whereas in Urania and Canna they are nearly the T ^th. 



