CYCADS 



323 



plants the^ protoxylem is immediately adjacent to the pith 

 (cf. p. 79). 



Cycads often attain a great age and their stems exhibit 

 secondary growth, with the same general plan of construction 

 as in a woody Dicotyledon, except for the absence of annual 

 rings. The pith is very large, and, in the Sago-palm, contains 



i 



Fig. 183. — Young plant of Cycas circinalis. [Photo : E. J. S.] 

 Fig. 184. — Young leaf of Cycas, showing spiral inroUing of the pinnse. 

 [Photo: E. J. S.] 



the stores of starch which are one of the sources of the sago 

 of commerce. 



The sporophylls are of two kinds, microsporophylls and mega- 

 sporophylls, and are arranged in distinct male and female cones, 

 borne on separate individuals. The microsporophylls are thick 

 scales vi'hich are spirally arranged (Fig. 185, A), and bear, on 

 their under-surface, numerous sporangia (Fig. 185, D), often 



