_Fronds._ A general acquaintance with the various types of fronds illustrated by recent Cycads is important to the student of fossils not only to enable him to compare existing and extinct forms but as affording safeguards against possible sources of error in the description and identification of impressions[41]. The vernation exhibits less uniformity than in Ferns: in _Cycas_ the rachis is straight and the pinnae circinately coiled (fig. 220, B, vol. +ii.+ p. 283); in _Zamia_ and _Stangeria_ the rachis is bent and the pinnae straight, while in _Ceratozamia_ and other genera both the axis and leaflets are straight. As Braun pointed out, there is as a rule no terminal leaflet, or it may be pushed to one side giving a forked appearance to the frond apex[42]. [Illustration: Fig. 384. _Cycas circinalis_, abnormal frond. (From a specimen in the British Museum.)] _Cycas._ The presence of a strong midrib and the absence of lateral veins are distinguishing features: the lower margin of the lamina is frequently decurrent (fig. 387, A). In _C. circinalis_ the pinnae may reach 40 cm. in length with a fairly uniform breadth of 2 cm. A frond of this species in the British Museum, not quite complete, has a length of 112 cm.: on the lower part of the rachis strong spines replace the leaflets and near the apex of the leaf concrescent pinnae form a continuous lamina traversed by seven ribs and dissected at the margin into acuminate teeth (fig. 384): some of the pinnae are forked as in _Cycas Micholitzii_[43] (fig. 385). Several years ago I noticed a similar instance of concrescence in a small plant of _C. circinalis_ in the Royal Gardens, Kew (fig. 387, I). In _Cycas Micholitzii_ the pinnae, reaching a length of 20 cm., are repeatedly and deeply forked (fig. 385, A, B; fig. 400): the pinnae of _C. Rumphii_ var. _bifida_[44] are also deeply dissected. _Cycas Beddomei_ has very narrow pinnae (15 cm. × 2 mm.) similar to those of the Wealden species _Cycadites Saportae_, and it is noteworthy that narrow leaflets with a strongly revolute lamina would produce casts with two parallel ribs (the grooves between the midrib and the edge of the lamina) simulating the double midrib of the fossil genus _Pseudocycas_. In some fronds, _e.g._ _C. Cairnsiana_, the midrib is hardly visible on the upper face of a dried pinna which shows a longitudinal wrinkling simulating parallel venation. [Illustration: Fig. 385. A, B, _Cycas Micholitzii._ (After Thiselton-Dyer.) C, _Zamia angustifolia._]