r 



^ 



t 



1907] 



BINFORD— SPORANGIUM OF LYGODIUM 



217 



walls are usually at right angles to the plane of the leaf. These 



i 



spora 



Fig. 13. The third division of the 

 initial cell. X980. — FiG. 14. The third 

 division completed. X980. — FiG. 15. A 

 section showing the cap cell cut ofF by 

 the fourth division. — Fig. 16. A section 

 showing the cap cell and a division of a 

 wall ceil. X980. — Fig. 17, A section 



perp 



endicular to the surface of the leaf 



\ 



showing the long axis of the cap cell. 

 X980. 



may be the result of the marginal initial cell. This question 

 naturally arises : Is the position of this cell such that the conditions 



which determine the direction of 

 walls cannot produce the usual 

 tetrahedral form? I know of 

 no other fern which has the spo- 

 rangia arising on the margin of a 



r 



4 



r 



Fig. 18. A longitudinal section of the stalk of the sporangium showing the stalk 

 to be very short. — FiG. 19. A cross-section of the stalk. X980. — Fig. 20. A section 

 of a sporangium showing the early division walls of the stalk and' wall cells. 



layer of tissue one cell thick. I found one instance in which the walls 

 were not at right angles to the lamina of the pinnule. 



