368 



MOSSES AND FERNS 



CHAP. 



other respects it is not likely that HyinenopJiylluni differs essen- 

 tially from the latter. The sorus occupies the free end of a vein, 

 which often continues to grow for a long time in Trichomanes, 

 and forms a long slender placenta or columella, upon which the 

 sporangia arise basipetally. While the receptacle is still very 



sp-- 



E. 



Fig. igi. — Tricliomancs cyrtotheca (Hilleb.). Development of the sporangium, X225. A, Longi- 

 tudinal section of very young receptacle with the first sporangia (j-/) ; B-D, successive stages of 

 development seen in longitudinal section ; F, horizontal section of nearly ripe sporangium ; r, 

 the annulus. 



young the tissue of the leaf immediately about it forms a ring- 

 shaped ridge, which grows up in the form of a cup-shaped 

 indusium, which either remains as a tube {Trichomanes) or is 

 divided into two valves (^HynieitopJiylhuii). Many species of the 



