414 



GYMNOSPERMS 



look like cups. In their axils, all the way around the axis, the stami- 

 nate llowers are borne. 



As in Welunlschia, ovulate flowers are associated with the stami- 

 natc, and the ovules develop much farther, producing megaspores, 

 which sometimes germinate. Such gametophy tes disorganize in early 

 free nuclear stages; occasionally they develop farther and even pro- 

 duce good seeds. In Welwitsch- 

 ia, the sterile ovules, although 

 reaching the size at which the ar- 

 chesporium appears in functional 

 ovules, show no trace of the begin- 

 ning of sporogenous tissue. The 



Fig. 386. — Gnetum gnemon: longitudi- 

 nal section of trachcids and parenchyma 

 of root, showing bars of Sanio; X375. 



Fig. 387. — Gnelum gnemon: longitudi- 

 nal section of two cells of root, showing 

 perforation which makes the lumen con- 

 tinuous; X375- 



staminate flower has a sterile ovule, and thus is bisporangiate. In 

 Gnelinn, the association is not so close, for there are no bisporangiate 

 flowers — only ovules and stamens in the axil of the same bract 

 (figs. 388). If the sterile ovule is only slightly developed, it does not 

 appear to inhibit the development of the microsporangia near it; 

 but when the ovule reaches such an advanced stage as that shown in 

 fig. 388 C, the microsporangia near it abort, and only those lower 

 down produce good pollen. In very rare cases, stamens have been 

 found in ovulate strobili. 



