284 DESC'IUPTIVE CATALOGUE 



Aptiana radiata, Slopes. 

 [Text-figs. 87-92.] 



1912. Aptiana radiata, Stopes, Phil. Trans. Roy. Soc. Lond., 

 ser. B, vol. 203, pp. 84-91, pi. vi, figs. 1, 3, 4, 5 ; pi. vii, 

 fig. 6 j pi. viii, figs. 10, 11 ; text-figs. 1-5. 



1912. Aptiana radiata, Janssonius & Moll, Proc. Sect. Soi. K. 

 Akad. Wetenschap. Amsterdam, pp. 623-026, text-fig. 1. 



Diagnosis. The species is founded on a stem, or branch, 

 3-5 cm. iu diameter. Primary wood without marked bundles]; 

 secondary wood with growth-rings, and consisting entirely of 

 fibre-tracheids with bordered pits, and of singly placed vessels 

 which are so arranged as barely to disturb the radial rows of 

 the fibre-tracheids and average 20-40 /u in diameter. Wood- 

 parenchyma, if present, scanty, and arranged beside the vessels 

 tangentially spanning the space between the rays. Medullary 

 rays numerous, multiseriate and uniseriate, the uniseriate rays 

 principally only two wood-fibres distant. Multiseriate rays 

 principally 3-4 cells wide, never running through a complete 

 radius of the stem, but dwindling to uniseriate rays or dying out 

 entirely ; those reaching the phloem expand to funnel-shaped 

 ends. Cells composing the rays of various types, end-cells often 

 much drawn out vertically. The phloem composed of scleriscd 

 elements and of soft cells in irregular alternating patches. 



HORIZON. Lower Greensand. 



LOCALITY. Probably Luccomb Chine, I. of Wight. 



TYPE. V. 11517, and sections V. 11517 a, b, c, d, e,f, </, h t 

 cut from it in the British Museum (Nat. Hist.). 



GENERAL DESCRIPTION. A short length (about 3 cm.) of the 

 stem is petrified in a dark medium in the coarse, glauconitic 

 sandy matrix characteristic of the Luccomb Chine and Shanklin 

 plant-beds in the Lower Greensand. The side of the specimen, 

 which is still embedded in the matrix, has the phloem and part of 

 the cortex preserved outside the wood (text-figs. 87, 88) ; the 

 centre of the stem is also present, so that the specimen is 

 unusually complete and its true diameter is known (4 x 3-5 cm.). 

 Petrified woods with their phloem and bark preserved are among 

 the rarest of fossils. The details of the elements are also 

 exceptionally well petrified, as can be surmised from text- 

 tig. 90, though no illustration can do justice to the beauty of the 



