124 



MORPHOLOGY OF GYMNOSPERMS 



phylls characteristic of Cycas (figs. 112, 114). In D. spinulosiim 

 and in Stangeria the sporophylls are still less leaflike, and the strobilus 



Fig. 114.- — Megasporophylls of cvcads: A, Cycas revoluta; B, Cycas circinaUs; 

 C, Cycas Normanbyana; D, Dioon edule; E, Encephalartos Preissii; F, Zamia integ- 

 rijolia; G, Ceratozamia mexicana. — A, after Sachs; C and F, after Von Muller; 

 E, after Miquel; F, after Richard; B, D, and G, drawn for Engler and Prantl's 

 Nat. Pflanzenj., from which the entire plate is taken. 



is much more compact; while in the remaining genera the sporophylls 

 show very little of the leaflike character and are organized into hard 

 compact strobili (fig. 92). 



In Cycas revoluta several ovules are 

 borne on the margins of the sporophyll 

 (fig. 114), as is also the case in C. circi- 

 naUs, in which the leafy portion is more 

 reduced; but even in the genus Cycas the 

 number of o^^lles becomes reduced to 

 two, as in C. Normanhyana and C. 

 siamensis (fig. 115). Two ovules are 

 characteristic of all the other genera, 

 with only occasional exceptions. The 

 two ovules are really borne on the margins, 

 but the sporophylls are so reduced that 

 they seem to be borne on the under sur- 

 face of a peltate structure (fig. 114, F, G). 

 In all the genera the ovules are sessile, but 

 in Dioon the crowding of the ovules in 

 the strobilus results in a stretching of the 

 tissue of the sporophyll so that it resembles 

 a stalk (fig. 116). 



Fig. 115.- — Cycas siamen- 

 sis: sporophyll with two ovules; 

 in the upper part of the sporo- 

 phyll the pinnules are united 

 into a solid mass, but the lower 

 pinnules are still free; one-half 

 natural size. — .\fter Miss 

 Stopes (42). 



