MORPHOLOGY OF SPERMATOPHYTES 



published his great monograph of the group, and incidentally 

 touched upon the stem anatomy of several genera. In 1861 

 Mettenius 4 published an account of Cycadean stems which has 

 remained until recently the chief source of information about 

 them. He included Cycas revoluta, Encephalartos horrida, 

 Dioon edule, and Zamia muricata, finding in the last two genera 

 none of the secondary cortical bundles characteristic of the first 

 two. In 1885 Costantin and Morot 15 published an account of 

 the structure of the pericycle of Cycas Siamensis, claiming that 

 in it the cortical cambium zones have their origin. In 1890 

 Solms-Laubach 17 published an account of Stangeria paradoxa, 



in which the vascular 

 bundles are traced from 

 the peduncles to their 

 juncture with the stem 

 system, and no evidence 

 of secondary cortical 

 bundles is found. In 

 1891 Strasburger 18 

 brought together the 

 knowledge of stem anat- 

 omy with reference to 

 Cycas, but did not in- 

 clude other genera. The 

 most important contribu- 



FIG. Z. titanqeria. paradoxa, staminate plant; tions to the knowledge of 



stem anatomy since are 

 those of Worsdell 21 - 30 

 on Macrozamia and Bowenia, and that of Scott 24 on the pedun- 

 cles of Cycads. 



The structure common to all of the stems investigated is a 

 large pith surrounded by a thick cylinder of open collateral 

 bundles and broad pith rays, and a conspicuous cortical region. 

 The primary bundles are common, and the primary cambium is 

 either short-lived or somewhat persistent. In Zamia, Dioon, 

 and Stangeria no further structures occur to interfere with the 

 resemblance to an ordinary coniferous or dicotyledonous stem, 

 and secondary thickening, whatever it may amount to, is effected 

 .by the primary cambium. 



A conspicuous feature of the structure of Cycas, Encephal- 



about one fifteenth natural size. From Warm- 

 ing-Potter's Handbook of Systematic Botany. 



