XL] BAIERA 47 



cannot always be distinguished from B. gracilis. The example 

 shown in fig. 651 from the Yorkshire coast has been named B. gra- 

 cilis forma Muensleriana to denote its close resemblance to the 

 Rhaetic species 1 . B. Guilhaumali 2 described by Zeiller from Rhaetic 

 rocks in Tonkin is another similar form but the leaves are narrower 

 and the apices of the segments more obtuse. On the one hand 

 Baiera gracilis approaches close to B. Lindleyana, a species charac- 

 terised by still narrower segments, and on the other it shades 

 into leaves agreeing with GinJcgoites sibirica. 



Baiera longifolia, (Pomel). 



Pomel 3 described this Jurassic species as Dicropteris longifolia 

 and Heer substituted the generic name Baiera' 1 . The leaves re- 

 semble those of B. Simmondsi in the division of the lamina into 

 narrow linear segments 2 9 mm. in breadth, but the leaf is 

 narrower and cuneate; the segments have obtuse apices. Heer 

 describes the veins as parallel and simple, 3 7 in each segment. 

 With this species Heer associates some male flowers similar to 

 those shown in fig. 654, also some detached seeds, but in neither 

 case is there any convincing evidence of connexion. The Siberian 

 species B. CzekanowsJciana 5 , recorded also by Moller from Bornholm, 

 is probably not a distinct type. Thomas 6 records B. longifolia 

 from the Middle Jurassic series of Yorkshire and gives new facts 

 with regard to the structure of the epidermal cells: one of his 

 specimens of an incomplete lamina is 12 cm. long, the whole leaf 

 being at least 18 cm. in length. The epidermal cells have a very 

 thick cuticle; those on the lower surface are arranged in longi- 

 tudinal rows and most of them have a prominent papilla; on 

 the lower face the cells are more rounded or hexagonal and the 

 stomata are much more numerous ; each pair of guard-cells is 

 surrounded by a group of 5 6 subsidiary cells (fig. 647, C, 

 D) as in Ginkgo. Krasser 7 records this species from Jurassic rocks 



1 Seward (00) B. p. 264. 2 Zeiller (03) B. PL L. figs. 1619. 



3 Pomel (49) p. 9. 



4 Heer (77) ii. p. 52, PI. vn. figs. 2, 3; PI. vm. ; PL ix. figs. 111; PL x. 

 figs. 6, 7; PL xv. fig. 11 6. 



5 Ibid-, p. 56, PL x. figs. 15; PL vn. fig. 1; (82) B. PL m. figs. 48; Moller 

 (03) PL v. fig. 3. 



6 Thomas (13) p. 243, PL xxv. figs. 3, 4. 



7 Krasser (05) p. 18, PL i. fig. 16. 



6 Thorn 



