THE REPRODUCTIVE STRUCTURES 89 



than ninety pounds. These cones are somewhat egg- 

 shaped. 



In Macrozamia Denisoni the cones are about two 

 feet long and have a diameter of nearly a foot at the 

 base, tapering to six inches at the top. They weigh 

 from fifty to seventy pounds, and contain two hundred 

 to three hundred seeds so large that they are cut through 

 the middle, provided with hinges and a clasp, and used 

 as match boxes. 



In other cycads the cones are smaller, that of Dioon 

 spinulosum weighing twenty to thirty pounds; Micro- 

 cycas, according to Caldwell, up to twenty pounds; 

 Dioon edule, ten to fourteen pounds; while others range 

 down to less than an ounce in Zamia pygmaea. 



The female cone is composed of a large number of 

 modified leaves called sporophylls, which are arranged 

 spirally upon an axis. In Cycas these sporophylls are 

 quite leafhke and are loosely arranged, so that they 

 behave like a crown of leaves, and the axis which pro- 

 duced them continues its growth, producing crowns of 

 foliage leaves and occasionally a crown of sporophylls. 

 Many do not like to call this crown of sporophylls a 

 cone. It is true that Cycas is the only cycad in w^hich 

 the axis is continued through the crown of sporophylls, 

 but the same phenomenon is frequently found in highly 

 developed cones of lycopods and conifers. However, 

 the transition from the Cycas type to a highly developed 

 cone in which the sporophylls bear little resemblance 

 to foliage leaves is not abrupt, for there is an instructive 

 series in the evolution of the compact cone from a crown 

 of loosely arranged sporophylls. Various stages in this 

 evolution are described and illustrated in chapter ix. 



