252 GYMNOSPEKM.-T:. 



This Division embraces three classes: CTCADEJB, CONIFERS, and 

 GNETEJ;. It is no doubt monophyletic, and has taken its origin 

 from heterosporous Ferns, now extinct, most nearly related to the 

 Ophioglossaceae and Marattiaceoe. The Cycadeee appear to be the 

 oldest class. The Conifers are related to these through Ginkgo. 

 The Gnetacea? are more isolated. The Division is not continued into 

 the higher Flowering-plants ; it has evidently attained its highest 

 development, and is now in a retrograde condition. The similarity 

 which ha's often been pointed out between certain Coniferse and 

 Lycopodinae is only in analogous resemblances, and does not entitle 

 one to suppose that there is a nearer relationship, or that the 

 former take their origin from the latter. 



Class l. Cycadeas. 



The stem is very rarely ramified. The leaves are large, pinnate, 

 and arranged spirally. The flowers are dioeciotts, without perianth. 



There is only one order, the Cycadacese. In habit they 

 resemble the Ferns, especially the Tree-Ferns (compare Figs. 207 

 and 256). The stem is tubercular (Fig. 258), or cylindrical (Fig. 

 256), but not very tall (as much as about 12 metres), and very 



itf 



FIG. 256. Cycis circinalis (female plant). The carpels are seen hanging from the top of 



the stem. Three leaves with the leaflets still rolled up project almost vertically into the 

 air, from the centre of the crown. 



rarely ramified. [In Ceylon, unbranched specimens of Cycas are 

 rarely met with in the wild state. The stems of C. circinalis 

 occasionally branch in greenhouses.] 



The LEAVES are arranged spirally, and so closely together that 

 no free stem-surface is left between them, and have only a slight 

 sheath (which is not amplexicaul, as in the Palms) . They are com- 



