XXVIIlJ FRONDS 19 



broad and short pinnae of 2, furfuracea^ bear a close resemblance, except in 

 the absence of an auriculate base, to those of some' species of the fossil genus 

 Otozamites. The broadly linear pinnae of Z. pseudoparasitiea (45 cm. x 3 cm.) 

 often show longitudinal wrinklings on drying which suggest comparison with 

 the corrugated lamina of the fossil species Nilssonia brevis. A basal pad or 

 callosity on the slender bases of the pinnae is characteristic of many Zamia 

 fronds. 



Oeratozamia. The fronds bear a fairly close resemblance to those of 

 Macrozamia : in Ceratozamia mexicana the linear pinnae reach a length of 

 over 30 cm. and a breadth of 2 — 3 cm. ; the lamina tapers to a narrow apex 

 and is more abruptly contracted at the base (fig. 387, H). The veins in 

 Ceratozamia are sub-parallel and dichotomy occurs up to the middle of the 

 lamina^. A striking feature is the occurrence of two opposite stipule-hke 

 projections a short distance above the base of the petiole. 



Macrozamia. A noteworthy feature in some species is the attachment 

 of the linear pinnae along the middle Une of the raohis (fig. 387, C) ; in others 

 (fig. 387, B) the leaflets are attached laterally and may have a basal callosity. 

 The parallel veins, which branch dichotomously near the base of the lamina, 

 are often much more prominent on the lower than on the upper face. In 

 M. heteromera^ (fig. 396, F, P') the narrow pinnae are deeply forked and 

 strongly revolute. The spirally twisted rachis of M. spiralis, M. heteromera, 

 etc., is a striking feature recalling the Rhaetio fern Camptopteris spiralis 

 Nath«. 



Dioon. The arrangement of the linear pinnae of D. edule (fig. 386, B), 

 D. spinuloswm, and D. Purpusii^ forms a ready means of distinguishing the 

 fronds of this genus: the pinnae, often contiguous and at right-angles to 

 the raohis, are attached in a- lateral groove by an expanded and slightly 



decurrent base. The difference between the lower and upper face of a frond 

 (fig. 387, E, F) affords a good illustration of a common source of error in the 



identification of fossil specimens. The leaflets of D. spinuloswm, which 



except in their spinous margin are very similar to those of D. edule, may 



reach a length of 15 cm. and a breadth of 8 mm. The parallel veins are 



unbranched*. 



Microcycas'' . The pinnae of this genus, very like those of the Wealden 



species Zamites Buchianus, reach a length of 20 cm. and a breadth of 8 mm. ; 



on falhng they leave oblong scars resembling those on the rachis of Encepha- 



lartos. 



Stangeria. This genus is particularly interesting lieoause of its fern-like 



habit and venation. The large fronds of S. paradoxal bear broadly hnear 



1 Boi. Mag. 1818, Tab. 1969. ^ Matte (04) p. 34. 



« Seward (95) A. p. 5 ; Robertson (02) fig. 4. 



' Vol. n. fig. 287, p. 389. = Chamberlain (09). 



* Braun, A. (75); Bomemann (56) A. PI. x. 

 ' Caldwell (07); Caldwell and Baker (07). 



* Bot. Mag. 1859, Tab. 5121. 



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