262 



STRUCTURE OF LEAFY HEPATICS 



hepatics and probably stand nearer the ancestral type than any 

 other form. The Marchantiales represent a line in which the 

 tissues of the thallus have attained a considerable degree of 



FIG. 197. One of the leafy Jungermaniales, Porella: A, branch of the 

 plant bearing several sporophytes. B, under surface of a branch, showing 

 tjie lobing of the leaves and a row of minute scale-like leaves. C, portion 

 of a branch bearing an archegonium surrounded by cup-like perianth with 

 minute involucrate leaves at base. D, branch with cone-like antheridial 

 branchlets. At the left a single leaf is shown with globular antheridium 

 in its axis. E, section of a branch similar to C. The archegonium is seen 

 surrounded by the perianth and below the involucrate leaves. The sporo- 

 phyte is nearly mature and ready to elongate. It consists of a round cap- 

 sule containing elaters and spore mother cells that are dividing to form 

 four spores each. Below the capsule is the stalk or seta which ends in a 

 foot buried in the tissues of the branch. At the right is an unfertilized 

 archegonium that shows the original position and size of this organ. 

 H. O. Hanson. 



