﻿86 



VEGETATIVE FEATURES. 



PREFOL1ATION. 



As removed, each leaf, with its still folded, non-emergent pinnules, formed 

 an erect subcylindrical or spindle-shaped body with a long diameter of 15 mm., 

 coinciding with the radius of the trunk, and a short diameter of 1 2 mm. at right 

 angles to it ; all being deeply embedded in the luxuriant growth of ramentum. 

 The rachis was erect and distal to the mass of attached pinnules, the latter being 



folded inward in two closely packed imbri- 

 cating ranks in such manner that their upper 

 surfaces all faced towards the axis of the 

 trunk. That is, each pinnule stood erect with 

 its dorsal surface appressed at full length to 

 the ventral surface of its next higher neigh- 

 bor on the same side of the rachis, as in all 

 erectly prefoliate, once-pinnate cycad fronds. 

 To parallel this disposition of parts, 

 then, imagine the several pinnules of a nor- 

 mally expanded, once-pinnate frond of a liv- 

 ing cycadean trunk to be folded inward with 

 their dorsal surfaces toward the axis of the 

 trunk, so as to form two vertical ranks side 

 by side, one on each side of the rachis, just 

 as in figures 44 and 46, showing emerging 

 fronds of Dion and Macrozamia. The hypo- 

 thetical frond with a reduced number of pin- 

 nules, shown in figure 49, 1, also illustrates 

 the present erect entirely simple type of 

 prefoliation. 



Let us next observe that in some species 

 of the erectly prefoliate Macrozamia, the still 

 folded pinnules reach a nearly full size, while 

 the rachis yet remains short and entirely em- 

 bedded in the armor. The final growth and 

 emergence of the frond in this genus there- 

 fore consists largely in rachial elongation 

 with a lateral outward and forward swing of 

 the pinnules into their normal foliage posi- 

 tion, in sharp contrast to Dion, in which, 

 although erectly prefoliate, the rachis begins 

 to elongate markedly while the pinnules are 

 yet quite small. But from the comparative 

 size of various pinnules borne on non-emer- 

 gent rachides of Cycadcoidca ingens (type), as 

 will be shown presently, an intermediate con- 

 dition is indicated. These pinnules would 

 have increased markedly in size after emer- 



Fjg. 48. — Prefoliation and frond emergence of 

 existing cycads. Type III. 



Macrozamia spirali (?). Xf- Summit of trunk 

 bearing a partially emergent erectly prefoliate 

 young frond, with the surrounding older fronds 

 partially or wholly cut away. The fronds of 

 this specimen appear to emerge one at a time and 

 nearly continuously, with the production of few 

 or no scale leaves. The pinnules reach a nearly 

 mature size before the main rachial elongation 

 takes place, this being the type of frond emergence 

 characterizing Cycadeoidea and Cycadella. 



