

40 GINKGOALES 



B. longifolia Heer and other similar species in the smaller number 

 of segments. There is no petiole but the leaves are attached by 

 a narrow basal portion to a short axis (fig. 646). The occurrence 

 of several leaves on a very short scale-covered dwarf-shoot is an 

 interesting feature which affords evidence of relationship with 

 Czekanowskia and Phoenicopsis. Baiera paucipartita is described 

 by Yokoyama 1 from Rhaetic beds in Japan and an imperfect 

 specimen from Rhaetic strata in New Zealand has been assigned 

 by Arber 2 to this species. In the case of imperfect leaves it is 

 impossible to distinguish specifically between many 'species' of 

 Baiera characterised by the division of the lamina into bilobed 

 linear segments. 



Baiera spectabilis Nathorst. 



The leaves of this Rhaetic species from the south of Sweden 3 

 reach a length of 25 cm. ; the coriaceous lamina is obcuneate and 

 fan-like but narrower than the leaves of such a species as B. Sim- 

 mondsi. There is no well-defined petiole ; the lamina is deeply 

 divided into two symmetrical halves each of which is further sub- 

 divided into bifurcate linear segments, and the strongly contracted 

 ultimate segments are a characteristic feature (fig. 647). The 

 basal region forms a stalk-like portion varying in length and, in 

 the specimens so far obtained, not exceeding 3 cm. The veins 

 are parallel to the sides of the segments and on the average 1 mm. 

 apart; they are occasionally dichotomously branched. Stomata 

 occur on both sides of the lamina but are more numerous on one 

 surface, presumably the lower; the guard-cells are slightly de- 

 pressed and surrounded by 5 6 subsidiary cells with thickly 

 cuticularised papillose walls (fig. 647, B) as in Ginkgo. The epi- 

 dermal cells on the lower surface are also papillose like those 

 described by Thomas in B. longifolia*. Several dark spherical and 

 spindle-shaped patches found by Nathorst between the cuticular- 

 ised layers are believed to be the remains of some resinous or other 

 substance comparable with that formed in the secretory tracts in 

 the leaves of Ginkgo and some species of Ginkgoites. 



Baiera spectabilis is one of the larger forms of the species ; it 



1 Yokoyama (05) PL n. fig. 5. 2 Arber, E. A. N. (13) PL vn. figs. 2, 3. 



, 3 Nathorst (06). 4 Thomas (13) PL xxv. figs. 3, 4. 



