THE VEGETATIVE STRUCTURES 



79 



THE LEAF 



The beautiful crown of leaves is the feature which 

 gives the cycads their popularity as decorative plants. 

 Even the seedlings would be 

 popular if they were better 

 known, for a seedling of 

 Dioon spinulosum three or 

 four years old has four or five 

 graceful leaves, and the plant 

 is easy to keep, even in a 

 steam-heated house. 



The young leaves are 

 very delicate and susceptible 

 to injury during the rapid 

 growth, but after they have 

 attained their full size the 

 tissues harden, and they be- 

 come extremely strong and 

 resistent to extremes of dry- 

 ness and moisture. The 

 mature leaves of older plants 

 become very tough and 

 leathery, and their structure 

 is such that very little 

 moisture is lost from the 

 inner tissues, so that leaves 

 of some species keep bright 

 and green for a couple of 

 weeks after they have been 

 removed from the plant. 

 Leaves of Bowenia spectabilis 

 lying on the veranda of a hotel in the blazing, tropical 



Fig. 25. — Dioon spinulosum: 

 transverse section of mature 

 wood, showing a growth 

 ring (g). 



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