MORPHOLOGY OF SPERMATOPHYTES 



PART I.-GYMNOSPERMS 



CHAPTER I 



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CYCADALES 



Ix the present flora nine genera of Cycads are recognized, 

 containing between seventy-five and one hundred species, and 

 distributed about equally between the oriental and occidental 

 tropics. The group is of special interest on account of its fern- 

 like characters, but knowledge of the most critical structures is 

 confined to comparatively few genera and species. With the 

 establishment of laboratories in regions where Cycads are in- 

 digenous, and with the increased attention paid to their culti- 

 vation, there is every reason to hope that the group will soon be 

 fairly well understood, so far as its living representatives are 

 concerned. The following account merely summarizes the 

 meager information at present available, which may or may not 

 find general application in the group. 



The gross character which serves to distinguish Cycads from 

 other Gymnosperm groups is the combination of unbranched 

 stems with a terminal rosette of comparatively few large and 

 branched leaves, which gives to the columnar forms the habit of 

 tree ferns or palms (Figs. 1, 2, 3, 4). The most remarkable rec- 

 ondite character of the group, a character which it shares with 

 Ginkgo, is the occurrence of peculiar multiciliate male cells, 

 demonstrated as yet only for Cycas, Zamia, and Stangeria, but 

 probably common to the whole group. 



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