CYCADALES 



15 



\ 



of Cycads is worthy of note. In the parks of Chicago we ob- 

 tained a strobilus of Dioon edule which measured 30 centime- 

 ters in height and 20 centimeters in diameter ; and one of Cycas 

 revoluia which measured 50 cen- 

 timeters in height, and about 

 the same in diameter. 



In Cycas the sporophylls re- 

 semble the foliage leaves in gen- 

 eral form (Fig. 14), the strobilus 

 appearing as a rosette of much 

 smaller and yellowish leaves. 

 An interesting transition may 

 be traced from the leaflike spo- 

 rophyll of Cycas re valuta to 

 such specialized ones as those of 

 Zamia or Ceraiozamia (Figs. 

 14, 15, 16). In the sporophylls 

 of Cycas re valuta the upper 

 pinnae are prominent, but the 

 lowest ones, usually three on 

 each side, are replaced by spo- 

 rangia. In Cycas circinalis the 

 upper sterile pinnse are much re- 

 duced; while in Cycas Norman- 

 byana the terminal portion of 

 the sporophyll is merely toothed, the lowest pair of teeth being 

 replaced by sporangia. In Dioon and Encephalartos the sterile 

 portion is still leaflike, but it is entire, and a pair of sporangia 

 occupy a basal position; while in Zamia and Ceraiozamia the 

 sterile tip has become a peltate expansion, and beneath it is 

 the pair of sporangia. 



Investigations in reference to the development of the mega- 

 sporangium have been incidental to a study of the embryo sac 

 structures. Important among these contributions have been 

 those of Warming 8 ' 9 on Cycas in 1877 and 1879; of Treub llj 14 

 on Ceraiozamia and Zamia in 1881 and 1884; and most recently 

 of Lang 29 on Stangeria paradoxa. The authors have also had 

 the privilege of looking over material of Zamia kindly supplied 

 by Mr. H. J. Webber. From these accounts, and from per- 

 sonal observation, the general facts seem to be as follows: 



FIG. 12. Dioon edule, ovulate strobil- 

 us; surface view; x %. From pho- 

 tograph taken iu Lincoln Park, Chi- 

 cago. 



