516 



LIFE-HISTORIES 









f.^^ 





Flu. 340, I. — UmbrcUa-liverwort {Marchanlia pohjmorpha, Umljrella- 

 liverwort Family, Marchaniiacew) . Male plant bearing antheridia- 

 carriers (anthcridiophores) j. (Atkinson.) — The plant is common on 

 moist earth, rorks. etc., throushout the world. 



Fig. 340, II. — UnihrcUa-liv riwort. Top of antheridiophore {';), cut ver- 

 ticall,>' to show the cavities containing antheridia. (Atkinson.) 



body i.s carried away by some current of rain water and comes to 

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

 surface happens to be undermost, and Ijegins 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 

 cj'hndrical stalk and an expanded top. In male plants (Fig. .340 

 1-lV) this top is a lobed disk on the ujiper side of which are pits, 

 each containing a multicellular gametangiunt, from which come 

 slender motile gametes like those of Riccia already described. 

 .\rclicg<i;ii;i arise also on tlK> top of what isatlirsi a somewhat similar 



