Amphithecium 



Mature spores 



414 A TEXTBOOK OF THEORETICAL BOTANY 



The apex may have already dehisced longitudinally by the splitting of 

 the amphithecium into two parts, and have liberated its spores, while in 



the lower portion all stages in the 

 formation of the spores are still 

 to be seen. The valves twist 

 hygroscopically after dehiscence 

 and may thus assist spore dis- 

 persal. The basal portion of the 

 sporogonium is enveloped by a 

 tubular upgrowth of the arche- 

 gonial wall, forming a calyptra. 

 The growth and dehiscence of 

 the sporogonium continue as long 

 as the gametophyte lives, which 

 is in marked contrast with the 

 short-lived sporophytes of other 

 Liverworts. 



The lowest cells of the em- 

 bryo also divide, though less 

 vigorously, to form a rounded 

 mass, the foot, the outer cells 

 of which form short rhizoids, 

 penetrating the tissues of the 

 gametophyte, from which they 

 absorb nutriment. This forma- 

 tion of rhizoids from an actively 

 growing foot has suggested the 

 speculation that the sporophyte 

 might in this way become in- 

 dependent, the foot penetrating 



spore rr^other cell the thin tissue of the thallus tO 



become a root in the soil and 

 thus establish the sporophyte as 

 a self-supporting plant. There 

 is no evidence, however, that this 

 interesting possibility ever be- 

 came a fact. Indeed a similar 

 development of rhizoids from the 

 sporogonium is know^n in some 

 Mosses where there is no likeli- 

 hood of the sporogonium achiev- 

 ing independence. Moreover in 



Columella , 



■\ 



Calyptra 



Foot 



Fig. 397. — Anthoceros laevis. Longitudinal section 

 through sporogonium and calyptra. 



the Fern embryo, where there is an actual root, there is also a foot, which is 

 quite a distinct structure. 



