Chapter XV. 



Liverworts of Minnesota* 



Mud-flat liverworts. The lowest family of liverworts is char- 

 acterized by a flat and prostrate leafless plant-body, such as may 

 be seen in the little circular forms growing upon mud-flats. 

 These may be recognized as different from lichens of similar 

 habit by their bright green color unmodified by any tint of gray 

 or blue. They occur as discs an inch or so in diameter and are 

 made up of forking flat stems seeming to radiate from a com- 

 mon centre. The upper side has 

 a spongy look which is caused 

 by the existence of air-cham- 

 bers in the plant-body. At 

 the edge of the disc are the 

 ends of the forking branches 

 and each of these is notched, 

 while at the bottom of such 

 notches lie the growing-points 

 of the branches. The tip cells 

 of a branch do not divide so 



fast aS the Older Cells and thus FlG - 43 - Mud-flat liverwort, showing method 



of growth and branching. After Atkin. 



the older parts protrude be- so ,i. 

 yond the true tip. This ex- 

 plains why the tips of all the branches in this family of liver- 

 worts are notched. 



Floating liverworts. A close relative of the mud-flat liver- 

 wort, of which there are several different species in Minnesota, 

 is the floating liverwort. The plant-bodies of this variety are 

 found in ditches and small pools of water. Sometimes in lakes 

 they are found entangled among the cat-tails and bulrushes 

 along the water's edge. The plant consists of delicate forking 

 branches of a bright green color, sometimes gathered together 



