Minnesota Plant Life. 133 



by the waves into masses as large as one's hst. The branches 

 are ribbon-like and generally not more than a sixteenth of an 

 inch wide, but they may be an inch or more in length. It is 

 impossible to mistake this plant for an alga or for any form 

 of duck-weed if one observes the notch at the tips of all the 

 branches. The three-pronged duck-weed, which is often found 

 wath it. is a flowering plant and may be recognized by the con- 

 vex ends of its little flat branches and the greater breadth of the 

 stem in comparison with its extension. 



Swimming liverworts. Another form of lower liverworts is 

 the swimming liverwort, which might be mistaken for a duck- 

 weed since it much resembles it in habit. It is its custom to 

 float in large patches upon the surface of quiet pools. Each 

 plant dangles from its underside a tuft of root hairs into the 

 water thus obtaining special absorptive areas and counterpoises 

 against being turned upside down by the wind. The swim- 

 ming liverworts differ, however, from duck-weeds in being 

 somewhat heart-shaped, on account of their terminal notch, 

 while duck-weeds are rather oval discs or shaped something like 

 little trefoils as they lie upon or in the water. 



Cone-headed liverworts. The next higher family of liver- 

 worts has the same general character in the sexual generation 

 which has been described for the mud-liverworts and their allies, 

 but the plant-bodies are in many instances larger and more 

 perfected. The cone-headed liverwort is an example of this 

 group. It spreads out its broad forking branches of a dark 

 green color upon logs, clifTs and bowdders in wet places. Its 

 surface is marked by diamond-shaped areas in the centre of 

 each of which is seen a whitish dome-like eminence not much 

 larger than a pin-point. The width of a single branch is from 

 a quarter to three-quarters of an inch while it may be several 

 inches in length. On the under side are produced numerous 

 root-hairs and tiny purple scales along the conspicuous mid-rib. 

 When the cone-headed liverwort is fruiting, there will be ob- 

 served during summer and autumn certain green cone-shaped 

 branches close to the surface of the flat stem. In this condition 

 they remain throughout the winter, but in early spring the stem 

 of the cone-headed branch elongates into a pale stalk a couple 

 of inches in height and about a sixteenth of an inch in diameter. 



