CYCLADENIA 197 



(1) midrib, no lateral nerves: Cycas. 



(2) midrib and lateral nerves : Stangeria. 



(3) numerous parallel or wavy, simple or forked nerves running 



longitudinally: the other genera. 



The fls. are dioec. and usu. take the form of cones ; these art: 

 term., and so the stem becomes a sympodium, except in Cycas and 

 some spp. of Encephalartos, &c., where the stem 'grows through' 

 the fl or fls. The size of the cones varies considerably. Each 

 consists essentially of a central axis bearing a number of fertile 1. or 

 sporophylls; occasionally the lowest 1. are sterile as in Coniferae. 

 In the <? cone, the 1. (scales) are generally of a sort of nail shape 

 (cf. Equisetum), and bear sort upon the lower side, each of 2 6 

 sporangia (pollen-sacs), arranged with the lines of dehiscence radiating 

 from the common centre. In the cone the scale (cpl.) is of some- 

 what similar shape but bears as a rule only two sporangia (ovules), 

 whose apices are directed towards the axis of the cone. Cycas (q.v.) 

 has no proper cone, but the stem bears a whorl of cpls. in place of 

 ordinary 1. The ovule is large, orthotr. with one integument. The 

 pollen is carried by the wind to the micropyle, where it germinates. 



The ov. grows into a large seed; testa two-layered, the inner 

 woody, the outer fleshy. Endopleura on the seed. Nucellus reduced 

 to a thin cap on the top of the seed, the bulk of which is endosp., 

 with straight embryo in centre. 2 cots., usu. united at the tips. 



The C. are exclusively trop. and subtrop. Of the genera, 4, 7, 8, 

 9 are from Am., 3 and 6 Austr., 2 and =, Afr., whilst Cycas is found 

 in E. Ind., Austr., and the islands of Ind. and Pacif. Oceans. 



Classification and Genera (after Eichler) : 



I. Cycadeae (cpls. with 84, rarely 2 ovules; stem growing 

 through the ? fl. ; leaflet with midrib only): i. Cycas. 



II. Zamieae (ovules 2; stem not growing through) : 

 Pinna pinnately nerved 2. Stangeria. 



,, longitudinally nerved 



Leaf bipinnate 3- Bowenia. 



,, once pinnate 



Ov. on swelling of cpl. 4. Dioon. 



,, sessile 



Scales peltate. Afr. 5. Encephalartos. 



,, pointed. Austr. 6. Macrozamia. 



,, peltate. Am. 7. Zamia. 



,, two-horned 8. Ceratozamia. 



,, in 3 flat, in ? peltate. 9. Microcycas. 



Cycas L. Cycadaceae. 16 trop. E. Ind., Austr., Polynes. For gen. 

 char., &c., see fam. The 9 pi. does not bear a cone, but a whorl of 

 cpls. of a woolly brown appearance; in notches upon the margins of 

 these are the naked ovules, usu. 4 8 in number. Stems reaching 

 50 ft. in some sp., usu. unbranched. The pith of C. circinahs L. 

 (trop. As., sometimes called sago-palm) and C. revoluta Thunb. 

 (Japan) yields a sago. Literature in Coulter and Chamberlain, 

 Morphology of Gymnosperms (q.v.'). 



Cyclachaena Fresen. (Iva EP.). Compositae (5). 2 N. Am. 

 Cycladenia Benth. Apocynaceae (n. i). 2 California. 



