26 



MORPHOLOGY OF GYMNOSPERMS 



radiate sorus (fig. 20). At maturity, the tips spread apart, forming 

 a hanging fringe from the under surface of the blade, which then 

 "resembles an epaulet" (fig. 21). In transverse section each spo- 

 rangium is seen to be composed of two loculi, circular in section and 

 separated by a thin partition. The accompanying diagrams (figs. 22 



Fig. 19. — Crossotheca Hdninghausii: portion of frond with several "stamens," 

 some of which show the individual sporangia; X4. — From photograph by Kidston 

 (64). 



and 23) show longitudinal and transverse sections of this stamen. 

 Dehiscence takes place by a longitudinal slit along the adaxial face, 

 the spores of both loculi thus being liberated simultaneously. The 

 microspores are 50 to 75 /a in diameter, having a surface rough with 

 blunt points. 



The discovery described above raised the question whether all 



