﻿CHAPTER IV. 



TRUNK STRUCTURE. 



ARMOR. 

 RAMENTUM. 



A luxuriant growth of ramentum forms one of the conspicuous outer features 

 of most cycadeoidean trunks. Borne over and densely packed between all the 

 lateral leaf, peduncle, and bract surfaces, as well as thickly enveloping the entire 

 crown and even drooping over and quite covering the trunk surface, as in some 

 forms of Cycadella, the ramentum may make up quite half the entire bulk of 

 many trunks. It is usually preserved in most perfect detail, doubtless the result, as 

 already suggested, of the free percolation of silica-laden solutions through the hairy 



Fig. 16. — Cycad and fern ramental types. 

 Seward. 



a, Dion edule. Longitudinal view of an epidermal 



hair, showing its base. > 150. 



b, Cyathea excelsa. Transverse section of a ram- 



ental scale. X 35. 



c, Cycadeoidea gigantea. Transverse section of a 



group of ramental scales. X 35. 



Fig. 17. — Encephalartos villosus. X 9. 



The woolly "Cafferbread," a branching cycadean trunk 

 with three strikingly villous crowns, comparable to the 

 ramentum-covered crowns of the Cycadeoideae. 



to silky ramental mass. At least such solutions could not so readily make their 

 way through the woody outer layers of the leaf bases before a breaking down of 

 tissues began in the absence of silicifying action. 



While ramentum has not been found absent in any of the Cycadeoideae, some 

 of the trunks bear but little, and present nearly as conspicuous a series of leaf-base 

 spirals as the more directly comparable existing cycads without numerous scale 

 leaves. In most species by far the larger part of the outer or armorial zone of the 

 trunk is made up of ramentum. The length of the ramental scales usually varies 



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