XXX VI] VECTIA 419 



Vectia. Stopes. Genus incertae sedis. 

 Vectia luccombensis Stopes. 



The generic name Vectia has been given by Dr Stopes 1 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 



s. 1 



Tf-c.s. s 2 i 



V I m. sp- 



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

 fibres, s 1 , s 2 , and radial pairs of pitted elements, v 1 and v 2 ; m, medullary -ray 

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

 adjacent fibres; /, 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. 7275. 



272 



