OF LOWER GREENSAX1) PLANTS. 247 



INCERT^ SED1S. 



Genus VECTIA, nov. 



The specimen about to be described cannot be included in any 

 known genus of fossils. The specimen consists of one kind of 

 tissue only, so that true generic diagnosis cannot be attempted. 

 It was found in the Isle of Wight, and consequently the name 

 Vectia appears suitable as the pseudo-generic name requisite till 

 further portions of the plant are discovered and reveal its 

 structure sufficiently for true diagnosis. 



Vectia luccombensis, sp. nov. 

 [Plates XXIII-XXV ; text-figs. 72-75.] 



Diagnosis. Species founded on a massive secondary tissue 

 which appears to be phloem. The tissues are extensive, uniform, 

 and part of a large trunk. The deceptive appearance of annual 

 rings is obvious to the naked eye, and is really formed by 

 narrow, regular, cork bands which do not break up the tissue ; 

 a thickness of 26 mm. and probably more, holding together 

 uniformly and showing no limiting layer. The tissue is entirely 

 composed of regularly alternating thick and thinner walled 

 elements, arranged in tangential bands. The fibres average 

 40-50 fj. in diameter, are squarish in shape, and have walls so 

 thick that only a minute lumen is left. The thinner vessels 

 (sieve-tubes?) are in radial pairs, with large round pits in single 

 rows in their radiul walls. Adjacent elements generally appear 

 contiguous, but in the angle between four of the latter elements 

 small parenchyma-cells, somewhat elongated and with straight 

 end-walls, may occur, and in some places these are tangentially 

 united by narrow crushed elements, which may be collapsed 

 portions of one of the cells. Medullary rays are entirely 

 imiseriate, the individual cells of the ray large, with nearly 

 rectangular end- walls. 



HORIZON. Plant-band, Lower Greensand. 



LOCALITY. Luccomb Chine, Isle of Wight. 



TYPE. V. 13230 and slides V. 13230 a, I, c cut from it in the 

 British Museum (Nat. Hist.), and slides SB. , b, c in the Stopes 

 Coll. ; also block and slide SBG. Stopes Coll. 



