THE SEEDLING OF CERATOZAMIA 



CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 1 15 



Helen A. Dokety 

 (WITH TWO FIGURES AND PLATES XII-XVl) 



The vascular anatomy of adult cycad stems is likely to be obscured 

 by two sets of complications. One, called anomalous thickening, 

 described by Von Mohl (14) in 1832 in species of Encephalartos, 

 is limited to certain forms; the other, the phenomenon of girdling, 

 was described by Karsten (5) in Zamia muricata Willd. in 1856, 

 and by Mettenius (8) in Cycas, Encephalartos, and Dioon in i860! 

 Since then it has been found in the three other genera investigated. 

 In the seedling these complications are either absent altogether or 

 are just being initiated, hence the selection of juvenile forms is proba- 

 bly even more important in the anatomical study of cycads than in 

 that of any of the other vascular plants. Anatomists have recognized 

 this and have given us numerous descriptions, only the more pertinent 

 of which need be cited here. 



In 1856 Karsten (5), in the work mentioned above, found that 

 each of the cotyledons of Zamia receives only one bundle, which may 

 branch; that the central cylinder is broken up by parenchymatous 

 communication between pith and cortex; and that in older stems, 

 with the increase in the number of cauline strands, there is a corre- 

 sponding increase in the number of bundles entering the leaves, 

 because every bundle of the central cylinder contributes a trace. 

 He also observed the frequent anastomosing of the leaf traces reported 

 by Von Mohl, as well as the occurrence of girdling. 



In 1884 Bower (i) wrote a few descriptive notes on the seedling 

 of Cycas Seemanni Al. Braun. He found the two cotyledons unequal 

 in size and dissimilar in vascular anatomy. He says that while in 

 some there is a median bundle which extends the whole length of the 

 cotyledon without branching, in others there are two equal bundles 

 near the center. 



In 1887 Gregg (4) reported anomalous thickenings in the root 

 of this species. 



2 ° 3 ^ [Botanical Gazette, vol. 46 



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