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RELATIONSHIPS. 



bilus of Cycas is of the absolutely simple type, in which a secondary deciduous 

 strobilar axis is not differentiated from the main vegetative axis, the latter standing 

 in the peduncular relation, and continuing anew its growth after fructification. 

 This is the sole surviving example among existing seed plants of this primitive 

 and essentially filicinean arrangement, which must have been widespread if not 

 universal among the Paleozoic phanerogams. Obviously termination of reproduc- 

 tive and then of vegetative growth by lateral branches following the production 

 of carpellary leaves would be the first steps in the direction of true cycad cone 

 evolution. 



In outer appearance the cones of both sexes strongly resemble each other, 

 the ovulate strobili of Cycas always excepted. The latter may be noted in figure 

 102, while ovulate cones are shown in figures 4, 6, 134, and 135, and staminate in fig- 

 ures 4, 101, and 115. The ovulate axes may greatly exceed the staminate in length 

 and are quite uniformly more robust, but have fewer sporophylls. The size of the 

 cones varies from three to five centimeters in length in Zamia pygmaea to nearly a 



Fig. 124. — Typical microsporophylls and son o( existing Cycadaceae. 

 (From Engler und Prantl. after Blume and Richard.) 



A. Cycas circinalis : a, entire stamen (from staminate cone) as seen from beneath ; b. sporangia! groups or sori of the same, 



enlarged ; c, sori which have shed their pollen. 



B. Zamia integrifolia ; a, entire stamen seen from beneath ; b, apical view of sorus ; c, lateral view of same. 



meter in some of the Macrozamias ; the number of sporophylls from less than 30 

 to more than 600. At the base and summit of the cones small sterile scales are 

 present, though evidently only different from the fertile series in non-development 

 and infertility, and hence directly comparable to the numerous infertile scales of the 

 cycadeoidean cone. Also, what must be regarded as a true reversion has been 

 reported by Thiselton-Dyer in the case of an immense ovulate cone of Encephalartos 

 bearing at its summit a clear transition from fertile scales to sterile scales, and from 

 these to small but otherwise typical foliaceous fronds. Pinnule-bearing scales have 

 been observed in Zamia floridana, and are doubtless of not infrequent occurrence 

 in other cycadean species. (See figures 134 and 135 of these cones.) No instance, 

 however, has thus far been reported of bisporaugiate monstrous cones, such as 



