194 



PLANT MORPHOLOGY 



cession. The initial is a superficial cell that undergoes several transverse 

 divisions, resulting in a short filament. Then the terminal cell functions 

 as a dolabrate apical cell (one with two cutting faces), the lower segments 

 forming the stalk and the upper ones the rest of the antheridium. The 

 spermatogenous tissue is differentiated from the jacket cells by the forma- 

 tion of periclinal walls. The mature antheridia are long-stalked and 



C ' D E ^mmm^ F 



Fig. 158. Sphagnum. A, leafy stem with terminal cluster of sporophytes, natural size; 

 B, surface view of portion of very young leaf, X260; C, diagram showing how the leaf 

 cells divide, cutting off cells marked 1, and then cells marked 2; D, appearance of leaf after 

 these cells have been cut off; E, surface view of portion of mature leaf, showing the narrow 

 elongated cells with chloroplasts and the larger hyaline cells with pores and slender bands 

 of thickening, X300; F, longitudinal section of nearly mature sporophyte, showing the 

 capsule, neck-like seta, and the foot, X24. {After Chamberlain.) 



nearly spherical, opening irregularly to discharge their sperms (Fig. 

 157C). 



The archegonia appear at the apex of short branches that, like the 

 antheridial branches, arise at the upper end of the main shoot. They are 

 borne in groups of one to five, without paraphyses, and are stalked and 

 free. An archegonium arises directly from the apical cell, as in the 

 acrogynous Jungermanniales, and then several others may arise from the 

 last-formed segments of the apical cell. After a short filament has been 

 produced by the formation of walls that may be either transverse or 

 obliciue, the usual three vertical walls appear in the terminal cell, cutting 



