xxxvi] 



VECTIA 



419 



Vectia. Stopes. Genus incertae 

 Vectia luccombensis Stopes. 



The generic name Vectia has been given by Dr Stopes^ to some 

 petrified secondary phloem discovered by her at Luccomb Chine in 

 the Isle of Wight : the fossil is from Aptian beds. The mass of 

 phloem is 26 mm. in breadth and consists of regularly alternating 

 bands of thin-walled sieve-tubes and very thick fibres associated 

 with a little parenchyma (fig. 540). To the naked eye the specimen 

 presents an appearance suggestive of rings of growth but this is due 

 to the presence of bands of 2—3 narrow cells which are probably 



Fia. 540. Vectia luccombensis. Transverse section showing the alternation of 

 fibres, s^, s", and radial pairs of pitted elements, v^ and v^; m, meduUary-ray 

 cells ; a, parenchyma cell between four thin- walled elements ; sp, pits between 

 adjacent fibres; I, much reduced lumen of fibre. (After Stopes.) 



cork. The whole is penetrated by uniseriate medullary rays. 

 A striking feature is the regular alternation of single rows of 

 fibres with two bands of sieve-tubes; in places the two bands 

 of sieve-tubes are separated by 2 — 4 rows of very flat, presumably, 

 cork-cells, and similar bands may be adjacent to or pass obliquely 

 across the fibres. The elongated elements described as sieve- 

 tubes, though thin in comparison with the fibres, have thickened 

 walls and on their radial faces are single rows of circular pits, 

 often in pairs; these are almost certainly sieve-areas which have 

 1 Stopes (15) p. 247, Pis. xxm.— xxv., text-figs. 72—75. 



27—2 



