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LIFE-HISTORIES 



Fig. 340, I. — Unibiella-liverwort {Marchantia polymorpha, Umbrella- 

 liverwort Family, Marchantiacew). Male plant bearing antheridia- 

 carriers (antheridiophores) |. (Atkinson.) — The plant is common on 

 moist earth, rocks, etc., throughout the world. 



Fig. 340, II. — Umbrella-liverwort. Top of antheridiophore (,), cut ver- 

 tically to show the cavities containing antheridia. (Atkinson.) 



body is carried away by some current of rain water and comes to 

 rest in a favorable spot it sends out pseudo-roots from whictiever 

 surface happens to be undermost, and begins to grow into a new 

 thallus. After a while organs distinctive of the sex appear near the 

 growing end, and curving upward become differentiated into a 

 cylindrical stalk and an expanded top. In male plants (Fig. 340 

 I-IV) this top is a lobed disk on the upper side of which are pits, 

 each containing a multicellular gametangium, from which come 

 slender motile gametes like those of Riccia already described. 

 Archcgonia arise also on the top of what is at first a somewhat similar 



