﻿EXISTING AND FOSSIL CYCADS COMPARED. 



235 



TABULAR COMPARISON OF OVULATE AND STAMINATE CONES. 



The strobilar homologies between the existing and fossil cycads, as presented 

 and discussed in the foregoing pages, are brought together in the appended tabular 

 comparison. 



Ovulate Cone. 



Axis. 



Bracts . . 



Interstitial 

 organs. 



S p o r o - 



phylls. 



Ovules ... 



Cotyledons 



Cycadeoidea;. 



A short to elongate 

 branch of the main 

 stem. 



Linear-lanceolate, en- 

 sheathing, permanent 

 (order spiral). 



Present as abortive 

 sporophylls, numer- 

 ous. 



Terminal and subter- 

 minal to the axis of 

 cone. 



Radio-symmetric 



Terminal to the main 

 sporophyll. 



Two, fleshy, exalbu- 

 minous, little or no 

 endosperm. 



Cycadeae. 



Continuation of main 

 stem, or can be a lat- 

 eral branch of limited 

 growth. A series of 

 modified fronds is 

 borne apically on the 

 trunk in same spiral 

 order as foliage and 

 scale leaves. 



The ensheathing scale 

 leaves (= bracts) are 

 permanent. 



Abortive sporophylls at 

 base and summit of 

 cone only. 



Terminal and subter- 

 minal. 



Structure dorsiventral, 

 but ovuliferous seg- 

 ments radial. 



Terminal to segments 

 of sporophyll. 



..inn.' . 



A rather elongate 

 branch of the main 

 stem. 



Linear-lanceolate, en- 

 sheathing, fugacious. 



Sterile sporophylls at 

 summit of cone. 



Mostly lateral, upper 

 ones terminal to axis 

 of cone. 



Radial or subradial in 

 structure. 



Marginal or subdorsal 

 or terminal to nearly 

 eliminated segments 

 of sporophyll. 



Two hypogaeal, fleshy, One to three or more 



embedded 

 sperm. 



in endo- 



hypogaeal, embedded 

 in endosperm. 



Ginkgoaceae. 



A shoot ? 



[Reduced.] 



Absent. 



Terminal and lat- 

 eral, as seen in 

 abnormali ties. 

 Radial in struc- 

 ture. 



Terminal to main 

 sporophyll. 



Two to three hypo- 

 gaeal, embedded 

 in endosperm. 



Staminate Strobilus. 



Axis 



Bracts 



Interstitial or- 



gan-.. 



Sporophylls 



Synangiaorsori. 

 Pollen 



Cycadeoideae. 



Terminates as a shortened 

 ovulate cone to which the 

 microsporophylls form an 

 hypogynous disk. 



Linear-lanceolate, spiral or- 

 der, ensheathing. 



None 



Fronds of only moderate 

 reduction. 



Marattioid synangia 



Five-celled 



Cycadaceae. 



Remains primitively elongate, 

 a cone. 



Ensheathing, fugacious. 



Sterile sporophylls, at base 

 and summit of cone only. 



Fronds reduced to expanded 

 scale-like form of Zamiae 

 megasporophylls. 



Angiopteroid or paleopteroid 

 sori. ( Cf. figure 137.) 



Three or four ( ?) celled. . . . 



Ginkgoaceae. 



Elongate, open form, of 

 cone inversely com- 

 parable to ovulate 

 Zamiostrobus cones. 



None. 



None. 



Greatly reduced. 



Paleopterid or botryop- 

 terid. 



Three-celled. 



