﻿EXISTING AND FOSSIL CYCADS COMPARED. 



21 5 



are occasionally seen in conifers. The phyllotaxy (12) of the cones is either spiral 

 or alternately whorled. Encephalartos caffer (f and 5) has a 21 ''55, and Cyras 

 spherica {t) a 55 144 spiral. Whorled decussate forms are Zamia muricata 

 (2/5 to 2/9), Ceratozamia mexicana, ^(2/25 to 2.-23), Dion edule, ' (2/26 to 

 2/37). Variations in the number of sporophylls, as well as in their disposition, 

 may, however, occur within the same species and sex. 



The microsporophyUs (see fig. 124) of wedge to nail-like form, with the lateral 

 edges aligned by mutual appression, mostly terminate in a heavy, blunt, more or 

 less peltate hexagonal end ; but they are acuminately extended in the genus Dion, 

 and bear a pair of lateral horns in Ceratozamia. The free terminal surfaces are often 





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Fig. 125. — Son and synangia of the five existing genera ol Marattiaceae. 



A and B. Angiopteris crassipes Wall : A. sorus ; B, two sporangia, the one in surface and the other in lateral longitudinal view. 

 C, D, sorus of Archangiopleris Henryi Christ el Giesenhagen. Seen from beneath (C) and in transverse section CD). E, F, 

 synangium of Marattia fraxinea in full and transverse longitudinal view tcf. various text-figures of synangia of Cycadeoidea). 

 G, H. Kaulfussia a^sculifolia BI., circular type of synangium as bome on the frond (Gl. and as seen in median longitudinal 

 section (Hi; J, K, Danasa elliptica Sm., nearly embedded synangium as seen from beneath (the apical view), and in trans- 

 verse longitudinal section. I From G. Bitter (5) in Engler und Prand.) 



pubescent, in Dion strikingly so. Only the nether covered surface is sporaugial in 

 varying extent, being in Cycas quite continuously so nearly from the axial insertion, 

 but in Zamia distal and divided into two lateral fields, occasionallv further restricted 

 to the outer edge of the sporophyll. The number of pendent conifer-like sporangia 

 borne by a single sporophyll varies from fully a thousand in the larger forms to but 

 two or three on each of the lateral sporangial surfaces in some of the small-coned 

 Zamias. Of much significance is the fact that on closer inspection the sporangia 

 are often found to exhibit grouping in sori similar to those of Angiopteris. Three 

 to six sporangia in Cycas and from two to three in the Zamia groups are basally 



