LIFE HISTORY OF A LIVERWORT 221 



they twist with a jerking motion, which helps to project 

 the spores out to a distance from the parent plant. The 

 advantage of this is self-evident. 



201. Germination. — In some, if not all, species of 

 Anthoceros, the spores germinate best after a resting 

 period of several weeks or months. Early in germination 

 chlorophyll develops in a plastid contained in the spore, 

 and a germination- tube, or protonema, forms, long in 

 some species, shorter in others, and at the tip of this tube 

 a thallus develops. 



202. Summary of Life History. — The life history of 

 Anthoceros is, in outline, as follows (it is illustrated dia- 

 gramatically in Fig. 167): 



OUTLINE OF LIFE HISTORY OF ANTHOCEROS 



Anthoceros-plant (gamelophyte) 



Antheridia • Archegonia 



i 4, 



Sperms Egg 



Fertilization 



Oosperm (zygote) 



i I 



Embryo 

 4, 4, 



Mature sporophyte (mature zygote) 



i i 



5 pore-mother-cell 



Spore Spore Spore Spore 



I 



Protonema 



i 



Anthoceros-plant (gametophyte) 



Reduction 



