OF LOWER GREENSAND PLANTS. 185 



ifc crosses ; the end-walls are rather irregular and curve or slope 

 (text-figs. 51 & 52, mw.). The ray-cells appear to be all alike, 

 and there is no sign of differentiation into tracheids. 



AFFINITIES. In many respects this species comes very near 

 to C. vectense, Barber (see p. 169), and, indeed, superficially the 

 resemblance appears very strong, because both have the 

 well-marked " composite" rings on which Barber laid so much 

 stress, but these have been found in several other forms (see 

 e.-g. Viguier & Fritel, 1912). 



The principal differences which distinguish the new fossil 

 from C. vectense are : the well-marked stone-cells in the pith, 

 the larger size of the tracheids and their tendency to form 

 irregular groups (text-fig. 51), and the type of pitting in the 

 radial walls of the medullary rays. In C. vectense the ray-pits 

 are principally 1, sometimes 2, or perhaps 3 per tracheid -field 

 of definite uniformly-sized pits. In C. luccombense the pits 

 vary greatly in size and shape in the same tracheid-field, and 

 form typically groups of three or four. 



While no one of these differences is final as a diagnostic 

 character, taken together they constitute a good specific difference 

 in the present state of our knowledge, and I name the species 

 after the place in which it was found. 



With the Lower Cretaceous species C. Lennieri, described in 

 detail by Lignier (1907), there appears to be a true affinity. 

 Lignier mentions that there are from 3 to 6 small pits per 

 tracheid-field in the medullary rays of his species. Judging 

 from his rather diagrammatic figure, these also vary in size in 

 each group, as they do in our fossil. Probably the French and 

 this new English species find their nearest allies in each other. 



The species C. erraticum, described and well illustrated by 

 Mercklin (1855, pi. xiv), has irregularly-placed groups of three 

 or four small roundish pits, which in some degree resemble our 

 fossil, though in Mercklin's fossil the pits are much smaller in 

 proportion to the area of the tracheid-field. It is not likely on 

 other grounds that this doubtfully Tertiary species is identical 

 with the Lower Greensand form. Also the ray-pitting in the 

 Tertiary fossil described as Callo.rylon Hartigii by Andrii (1848) 

 is rather like that of our new fossil. Several other species of 

 Cupressinoxylon with groups of pits in the radial walls of the 

 ray, have been described by Knowlton and others, which to some 



