CYCAS. 387 



the Mesozoic Period), before Angiosperms had begun to 

 form the dominant larger vegetation of the earth, Cycads 

 were very abundant and very widely distributed. The 

 Cycads are the lowest of the living Seed-Plants, and in 

 some respects show marked affinities with the Ferns. 



545. General External Characters. Cycas revoluta, 

 a Japanese species, the pith of which yields a kind of sago, 

 is often cultivated in hot-houses in this country, and large 

 specimens may be seen at Kew and other botanic gardens ; 

 the leaves are sometimes used for memorial wreaths and 

 may be obtained from florists. 



In a large specimen, note 



(1) The general resemblance of the plant to a Tree- 

 Fern, various kinds of which can also be seen in botanic 

 gardens. 



(2) The relatively short, thick (up to nearly a yard in 

 diameter in old plants), and usually unbranched stem, 

 bearing at the top a rosette or crown of large foliage- 

 leaves. 



(3) The crowded leaf-bases and scales covering the 

 bare lower part of the stem. 



(4) The stout-leaf-stalk, bearing 011 either side a row of 

 narrow leathery green leaflets (pinnae) . 



(5) The strong midrib running up the middle of each 

 pinna, which is convex above and concave below 

 (revolute) . 



(6) At the top of the stem, in the centre of the rosette 

 of expanded leaves, there may be seen either 



( 7 ) A bud covered by scale-leaves, or 



(8) Young foliage leaves in different stages of ex- 

 pansion, with each of the pinnae rolled up in a cir- 

 cinate manner (the main leaf -stalk itself is not rolled 

 up), or 



(9) A male cone, not unlike the seed-cone of a Pine, 

 or 



(10) A series of carpels, pinnate leaf-like structures 

 covered with brown woolly hairs ; the male cones and 

 the carpels are borne on separate plants. 



