376 



MORPHOLOGY OF GYMNOSPERMS 



nate than in the ovulate strobikis) and a slender cylindrical strobilus 

 (figs. 419-422). The strobili are axillary or terminal, solitary or 

 fascicled or even paniculate. The staminate flower resembles that 

 of Ephedra, consisting of two coherent bracts investing a short axis 



that bears at its tip two spo- 

 rangia. In the staminate strobilus 

 of Gnetum also, as in Ephedra, 

 ovulate flowers are frequently 

 present. 



It is tempting to see in these 

 flowers (simple strobili) the 

 essential features of the angio- 

 spermous flower, and to relate 

 the strobilus to the catkin-like 

 inflorescences of angiosperms. 

 While the parts may hold the 

 same general relations, these 

 situations may have arisen in 

 many regions of the gymno- 

 sperms, and none of them may 

 have involved the history of the 

 angiosperms. 



421 420 



Figs. 420-422. — Gnetum Gnemon: 

 ovulate strobili; fig. 420, young strobilus 

 with six cuplike whorls, the ovules pro- 

 jecting beyond the dense tufts of hairs; 

 fig. 421, a later stage, with three ovules 

 much larger than the rest; two ovules 

 in the second whorl show very well the 

 projecting tip of the inner integument; 

 fig. 422, transverse view of the stage 

 shown in the previous figure. 



THE MEGASPORANGIUM 



In all the genera of Gnetales 

 the ovulate flower consists of a 

 single ovule invested more or less 

 closely by a pair of bracts that are 

 more or less connate in Ephedra, 

 and completely so in Welwitschia 



and Gnetum. In fact, so com- 

 plete is the coalescence and so close is the investment in Gnetum 

 that this envelope has been regarded as an integument. In every 

 case there are two integuments, appearing in basipetal succession, 

 the inner one forming the micropylar tube. The elongated and 

 projecting micropylar tube is a feature of the Gnetales, being 

 neither spirally coiled nor expanded at the tip in Welwitschia, as in 



