CYCADALES 1 21 



THE MEGASPORANGIUM 



The ovulate strobili usually occur singly in the center of the 

 crown (fig. 112), but sometimes, especially in Encephalartos, two or 

 more may be produced. The ovulate strobili of cycads are the 

 largest known, those of Dioon spinulosiim reaching a diameter of 

 23 cm., with a length of 50 cm. and a weight of 14 kg. The long and 

 comparatively slender strobilus of Microcycas sometimes reaches a 

 length of 94 cm., but is not so heavy; the weight of 9.5 kg. as well 

 as the length of 94 cm. reported by Caldwell (52) is exceptional. 

 The strobili of Encephalartos and Macrozamia are not quite so large, 

 and in Ceratozamia they are seldom more than 26 cm. in length; in 

 the remaining genera they are comparatively small, perhaps the small- 

 est being that of Zamia pygmaea, in which they may be less than 

 3 cm. in length. If the group of ovulate sporophylls of Cycas be 

 regarded as a strobilus, it may be the largest and heaviest of all; 

 but we have not had an opportunity to weigh it or to measure a fully 

 grown specimen. 



In all the genera except Cycas the megasporophylls are in compact 

 strobili, the first strobilus being terminal on the primary axis of the 

 plant, while all the others terminate secondary axes. Pearson (47) 

 states that in Encephalartos F rider ici-Guilielmi and in E. Altensteinii 

 there are three to six cones symmetrically arranged around the apex, 

 so that there is no sympodium, but the vegetative apex continues 

 the growth of the stem, as already noted in the staminate plants of 

 these species. In Cycas the sporophylls bear considerable resem- 

 blance to the foliage leaves, and are arranged like an ordinary crown 

 of foliage leaves, with the bud for the next crown in the center (fig. 

 113) ; hence the trunk of the ovulate plant of Cycas is always a continu- 

 ation of the primary axis, and never a sympodium as in all other 

 cycads, including the staminate plant of Cycas itself, and also except- 

 ing cases in which several cones may be arranged around a persistent 

 vegetative apex. It can hardly be doubted that the compact strobili 

 are a later development from the Cycas type. Occasionally, even 

 in compact strobili, the meristem, instead of producing the stunted 

 sporophylls which usually terminate the strobilus, produces sporo- 

 phylls resembling foliage leaves; and in EncepJtalartos Wieland (51) 

 figures a strobilus with transitions between the sporophylls and the 



