CYCADALES 



77 



Adult plants of Dioon, Ceratozamia, Microcycas, and Cycas are 

 always arborescent; Bowcnia and Stangeria are tuberous, with all or 

 most of the stem subterranean; while in Zamia, Macrozamia, and 

 Encephalartos, some species are arborescent and others tuberous. 



The tallest of all cycads is Macrozamia hopei. The Queensland 

 botanist, F. M. Bailey, gave the height as "20 to 60 feet," a Httle 

 more than 18 meters. A similar height assigned to Cycas media, in 



I'lG. 00. — Macrozamia nioorci: at Springsure; about 200 miles west of Rockhampton, 

 Queensland, Australia (November, 191 1). 



Engler's Pflanzenfamilien, was a mistake, since Cycas media does 

 not reach more than one-third of that height. Someone probably saw 

 the tall Macrozamia, thought it was Cycas, and so started the mis- 

 take. 



Dioon spinulosum grows in the dense rainy forest and is 6-10 

 meters high, with occasional specimens reaching a height of 1 5 me- 

 ters. Microcycas calocoma sometimes reaches a height of nearly 10 

 meters. None of the other genera are nearly so tall. Any arborescent 

 cycad more than 2 meters in height may be regarded as a tall speci- 

 men. 



