﻿EXISTING AND FOSSIL CYCADS COMPARED. 



193 



Trunks. — So far as can be seen 011 the outer surface, these Zamia trunks, as 

 first dug up, are rather smooth, and do not appear at first sight to possess the 

 outer armor of spirally-arranged leaf bases so characteristic of other cycadean forms. 

 Just below the petioles of the crown of leaves there is a thin and rough covering 

 of scattering scale-like bodies and fine hairy material. Below this the trunks appear 

 to be irregularly ridged horizontally, these ridges soon disappearing, so that the 

 lower half or two-thirds is quite smooth in most places, and the armor of old leaf 

 bases absent, the outer covering consisting simply in thin cuticle. 



Fig. 106. — Zamia floridana DC 

 la, 



Miami, Florida, Nov. 15, fully six months previous to fecundation. 



lb, 



Id, 



Entire plant. ■ Vs. a, main trunk (underground) ; b, position of an old branch ; c, secondary tap-root running out from main 



foliage-bearing trunk, which is itself secondary ; d, primary or original tap-root. 

 Cone (ten-ranked) seen in la. X 5i. 

 Transverse section of a different cone. X %. Eight sporophyllar ranks are seen. These cones vary much in size as well as 



in number of sporophyllar ranks, which may be odd or even. The number of sporophylls in each rank also varies. 

 Single sporophyll with ovules attached. ! j. 



Pinnule showing dichotomous venation. X 53. 



That these trunks do not differ greatly from other forms is shown in figure 108. 

 The scaly material below the crown of leaves, and, lower down, the horizontal 

 ridges just mentioned, are the remnants of a true rameutum which is constantly 

 disappearing below as the age and the size of the trunk increase. And when this 

 ramental material is lightly scraped off above, preferably from a vigorous young 

 trunk, the somewhat carrot-like or turnip-like appearance is lost, and the spiral 



