672 MR. W. C. WILLIAMSON ON THE HISTORY OF ZAMIA GIGAS. 



every ray exhibits two small parallel oval protuberances, each being about J inch Ion**, 

 and ibout £ inch wide. In the fossil itself these mark the position of two depressions 

 ( Plate LIII. fig. 3) in each ray, separated from each other by a slight prolongation of the 

 central ridge. The further prolongation of the mesial line can be detected in the direc- 

 tion of the centre of the entire organism,/, and on either side of it, especially when it 

 traverses the disk, are traces of a row of small circular pits (Plate LIL fig. 1), each beino 

 about tV mc h m diameter. The depth of these little pits is very slight, and their out- 

 line often wants definition; but they are sometimes so distinct as to establish the fact 

 that they formed a characteristic feature of the organism. I propose to call this struc- 

 tun- by the provisional name of the carpellary disk. 



Thug far I have confined myself to describing the specimens, without attempting to 

 draw from them any inferences. These have shown that we have an arborescent stem 

 marked with the rhomboidal scars of fallen leaves, as in Cycadece. We have leaves, the 

 Cycadean affinities of which no one disputes, springing from the summit of the stem; 

 thru we have a peduncle (Plate LIII. fig. 13) clothed with scales, identical with the 

 squama foliares of Link, the uppermost ones having been more elongated than the rest. 

 This peduncle sustained the involucrum, composed of verticils of similar but much longer 

 -ales or bracts, within which there arose a pyriform axis with a smooth exterior, sup- 

 porting a superficial layer of oblong cells arranged vertically on its outer surface. Supe- 

 iorly the axis contracted, and again expanding to form the lenticular disk, then shot up 

 into the pyramidal axis, and terminated in the corona. 



We find associated with the above fossils the radiating organism provisionally desig- 

 nated the carpellary disk, and of which a restored figure is given in Plate LIII. fig. 2, a 

 structure having many indications that it was the female reproductive organ of a gymno- 

 pm-mous plant. All the remarkable objects enumerated occur in the same blocks of 

 andstone, unassociated with any other plants to which they can be referred with any 

 show of probability. The inference that they are parts of one plant, though incapable of 

 proof, is forcibly suggested. Adopting this interpretation, I will venture on a few hypo- 

 thetical conclusions, such as may guide future observers either to their confirmation or 

 to a correction of my errors. At all events such suggestions will raise definite points for 

 turther investigation. 



Remembering the dioecious character of living Cycads, it is probable that the fossil 

 tonus were also dicecious. The two different organisms, restored in figs. 2 &13 (PlateLIIL), 

 may be the male and female reproductive organs of Zamia Gigas. Remembering further 

 the frequency With which the male organs are deciduous amongst living plants, we note 

 with interest the significant probability that the pyriform axis of fig. 6 was invested by a 

 deciduous anthenlorous tissue. The examples from which the restored diagram (fig. 2) 

 w - constructed, afford more positive evidence that they were female organs. They 



1 the bracts ol the female cones of living Cycads, with their pairs of ovules symme- 



tr^'oTfi "f G lt ^ tbQn P r0babl * that *" two oblong depressions on 

 < rH i 1 % f ^r! 011 ° VU1CS ' as indicate d in figs. 2 & 4, while the two parallel 



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trs of ith 



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