88 



MOSSES AND FERNS 



CHAP. 



from which arise upright flattened shoots which are repeatedly 

 forked, so that there is a remarkably close superficial resem- 

 blance to the fan-shaped leaves of certain Ferns, especially 

 some of the smaller Hymenophyllacere. This resemblance is 

 heightened by the very distinct midrib traversing each thallus- 

 segment. 



Setfual Organs. 



The sexual organs in both Aneura and Metzgeria are borne 

 on short branches, which in the latter arise as ventral struc- 



FIG. 40. Aneura pinnatifida. A, Horizontal section of the apex of a young antheridial 

 branch, Xs6s; x, the apical cell; ^, antheridia: B, transverse section of a young 

 archegonial branch, passing through the apical cell (x) ; ^, young archegonia, 

 X525; C, longitudinal section of a nearly ripe archegonium, X26a; D, E, 

 spermatozoide of Pellia calycina, Xi225 (D, E, after Guignard). 



tures, but in Aneura are simply ordinary branches that are 

 checked in their growth by the production of the sexual or- 

 gans, and not infrequently may grow out into ordinary 

 branches after the formation of the sexual organs has ceased. 

 In A. pinnatifida (Fig. 39, B), archegonia and antheridia are 

 usually produced upon separate branches, but may occur to- 

 gether. 



The origin of the antheridia can be readily followed in 



