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RELATIONSHIPS. 



such forms as the Japanese Cyras revoluta and the Australian C. media R. Br. 

 The first of these species has been reported as reaching a trunk thickness of i 

 meter, whilst the trunks of the latter, though of somewhat lesser diameter, reach a 

 height of 23 meters. Zamia P'bppigiana and Z. pseudoparastiica are Peruvian epi- 

 phytes, the latter species also occurring in Panama. In relative size, outer appear- 

 ance, and habit of growth, the cycads have changed but little since the Triassic. 

 Such tall unbranched forms as Cycadeoidea Jenneyana, as we have seen, bear much 



• • 



102 103 



Fig. 102.^Cycas Normanbyana to the left. Cycas media R. Br. the two cycads to the right— that in foreground 



bearing numerous carpellary leaves. These columnar Australian species include some of the tallest forms known, 



C. media reaching a height of 23 meters, and greatly exceeding any known fossil cycad in this respect. (From 



Engler und Prantl, after F. V. Mull. Phyt. Austr.. Bd. VII.) 

 Fig. 103.— Zamia van Houttei, X J. Nearly armorless type of trunk. Pinnules with notably large and broad 



blades. Compared with Z. Lindeni, figure 47B, this trunk affords a fine example of foliage variation marking two 



closely related species. 



the same relation to the lower-growing Cycadellas from the P.lack Hills Upper 

 Jurassic [Wealden equivalent] as do the taller species of Cycas to the pygmy 

 Zamias. 



The profounder changes undergone by the cycads since Triassic time having 

 been mainly in their fructification, it is usually difficult to identify fossil fronds 

 with certainty in the absence of fruits. Hence it is not surprising that few of the 

 living genera are positively known in the fossil condition. Eticcphalarlos Gorceix- 



