ANCIENT PLANTS 



example, the genus Stangeria, which was supposed 

 to be a fern when it was first discovered and before 

 fruiting specimens had been seen. 



The large compound leaves are all borne directly on 

 the main stem, generally in a single rosette at its apex, 

 and as they die off they leave . their fleshy leaf bases, 

 which cover the stem and remain for an almost inde- 

 finite number of 

 years. 



The wood of the 

 main trunks differs 

 from that of the 

 other Gymnosperms 

 in being very loosely 

 built, with a large 

 pith and much soft 

 tissue between the 

 radiating bands of 

 wood. There is a 

 cambium which adds 

 zones of secondary 

 tissue, but it does 

 not do its work 

 regularly, and the 

 cross section of an 

 old Cycad stem 

 shows disconnected 

 rings of wood, ac- 

 companied by much soft tissue. The cells of the wood 

 have bordered pits on their walls, and in the main axis 

 the wood is usually all developed in a centrifugal direc- 

 tion, but in the axis of the cones some centripetal wood 

 is found (refer to c, fig. 65, p. 97). 



In their fructifications the Cycads stand even further 

 apart from the rest of the Gymnosperms. One striking 

 point is the enormous size of their male cones. The 

 male cones consist of a stout axis, round which are spiral 

 :^eries of closely packed simple scales covered with pollen- 



Fig. 74. — Plant of Cycas, showing the main stem with 

 the crown of leaves and the irregular branches which 

 tome on an old plant 



