CYCADALES 



103 



duction of the sporophyll from the leafy condition to the peltate 

 structure, which reaches its extreme in Zamia, can be traced in great 

 detail through the various genera and species of the living cycads. 



There is no doubt that Cycas revoluta shows the most primitive 

 sporophyll condition in the family, producing a crown of sporophylls 

 just as it, and the other cycads, produce a crown of foliage leaves, 

 still leaving in the center a meristem to produce more leaves or 



Fig. 95. — Cycas revoluta: strobilus consisting of a loose crown of sporophylls still 

 retaining many pinnae in the upper portion. 



sporophylls. Thus, the original meristem continues from the em- 

 bryo to the death of the plant. Proliferation is seen, occasionally, at 

 the top of a male cone, and sometimes in other genera, where vegeta- 

 tive leaves, greatly reduced, but sometimes bearing leaflets, appear 

 instead of sporophylls. 



The megasporangium. — The megasporangia, or ovules* as they 

 are usually called, are all erect and have a single massive integument. 

 In Cycas circinalis and Macrozamia denisonii they reach a length of 



* The term "ovule" (little egg) was mistakenly devised to apply to the entire mega- 

 sporangium. It is short, convenient, and in general use but, like the term "cell," has 

 nothing else to recommend it. 



