i 9 o8] DORETY—CERATOZAM1A 217 



geria. Of course the whole question resolves itself into the possibility 

 of determining phloem in the absence of sieve plates. 



In the feature of anomalous thickenings, as in so many other 

 features, Ceratozamia appears to hold an intermediate position. 

 The extrafascicular cambium is clear and distinct, yet in plants with 

 two scale leaves, two expanded foliage leaves, and two or three leaves 

 developing, the secondary fascicular systems are entirely wanting. 

 The failure or delay of this cambium to function indicates that it is a 

 vestigial character. I have seen it in Zamia as clear and distinct, 

 though not so abundant, as in Ceratozamia. 



There seems to be great variation in the number of root poles 

 throughout the whole group of cycads and even in individual roots. 

 This variation, taken in conjunction with the fact that in Ceratozamia 

 the number depends upon the degree of development of the median 

 bundle of the aborted cotyledon, indicates that this character is not 

 to be depended upon as a phylogenetic one. 



Summary 



1. Ceratozamia is dicotyledonous, the second cotyledon being 

 aborted by gravity. 



2. The cotyledon is often lobed at the tip. It is multifascicular, 

 and all the bundles are derived from three. The wood is mesarch at 

 the base and exarch in the upper portion. Mucilage ducts usually 

 alternate with the bundles. 



3. The leaf traces are at first vertical; girdling follows upon 

 increase in radial growth of the enclosed leaves and stem apex. 

 The wood of the leaf traces is endarch in the central cylinder, but 

 becomes mesarch in the leaf base and remains so to the tips of the 

 pinnae. 



4. The scale leaves are aborted foliage leaves. 



5. The first-formed portion of the central vascular cylinder may 

 be a protostele. 



6. The stem is a sympodium. 



7. There are several layers of extrafascicular cambium, but in 

 seedlings two years old only the slightest trace of anomalous thick- 

 ening. 



8. The root is a delayed organ, and its four poles are inserted 

 upon the cotyledonary bundles. 



