BENNETTITALES 



55 



the Museum staff, with suggestions and corrections by Wieland 

 (fig. 46). The leaflike microsporophylls surround the comparatively 

 small ovulate strobilus. 



The time of flowering has been the subject of considerable specu- 

 lation. It has been noted that in some of the tallest specimens there 

 are strobili only in the upper part, and that these strobili are of ap- 

 proximately the same age. Furthermore, 

 in some there are no vegetative leaves at 

 the extreme tip, and no indication that 

 there would be any. If such leaves had 

 been present, they would have been dis- 

 covered, as Wieland found them in Cy- 

 cadeoidea ingens. From a very thorough 

 study, Wieland concludes that many of 

 the Bennettitales flower but once, and 

 then die. Such a behavior is well known 

 in angiosperms. The century -^X^xit, Agave 

 americana, flowers but once and dies; but 

 it does not wait a hundred years. Plants 

 from "suckers," about 3 years old, flower 

 in 5-7 years. The palm, Corypha umhra- 

 culifera, attains an age of about 40 years 

 and a height of 60 feet, when the axis is 

 suddenly prolonged another 40 feet as 

 an immense flower stalk bearing thou- 

 sands of flowers. The plant then dies. 

 Yucca whipplei flowers but once, and 

 dies; while other species of the genus 

 flower year after year. None of the living 

 cycads die on account of flowering. 



The microsporophyll. — The microsporophylls retain more of the 

 ancestral fern-leaf characters than any of the rest of the Cycado- 

 phyte line above the Cycadofilicales. They have about the same 

 topography as the vegetative leaves, but are much reduced in size. 

 The pinnules bear synangia on both sides, so that the pinnule looks 

 again pinnate. If the synangia are really reduced pinnules, as Wie- 

 land believes, the sporophylls are twice pinnate. Some strobili, 



Fig. 49. — Cycadeoidea daco- 

 tensis: longitudinal section of 

 sporangium showing stalk and 

 two loculi containing micro- 

 spores; X40. — After WiE- 



LAND.^^ 



