138 



Minnesota Plant Life. 



may be regarded as little two-forked branches modified by 

 the pressure of their mates in the cup, into the bi-convex form 

 which they have assumed. Growing among such gemmae at 

 the bottom of the cup are a number of mucilage-hairs which 

 produce a slime capable of swelling. By this, as soon as they 

 mature, the gemmae are lifted from their stalks and hoisted over 

 the edge of the cup. They are then carried away by rain-water, 

 or by currents if the plant is living in a ditch, to other places 

 suitable for the growth of umbrella-liverworts. It makes no 

 difference which 

 side of a gemma 

 falls toward the 

 ground. The un- 

 der side, after the 

 gemma has fallen 

 into position, pro- 

 duces root - hairs 

 which attach it to 

 the soil and the 

 upper side begins w 

 the development 

 of air - chambers 

 while the whole 

 branch increases 

 in size. In this 

 manner the plant 

 is abundantly 



propagated without the intervention of eggs, sperms or spores. 

 Another way in which liverworts propagate is much more anti- 

 quated than the gemma-method and probably suggests the origin 

 of gemma-propagation. As the general plant-body grows and 

 forks, the branches may become separated from each other by 

 the dying away of parts behind the forks. Thus ordinary branches 

 are isolated and if carried to a distance they may behave very 

 much as gemmae do. Ordinarily, however, they remain attached 

 to the soil and serve to propagate the plant only to adjacent por- 

 tions of the sub-stratum. The gemmae may be regarded as 

 tiny portable propagative branches and the apparatus for sepa- 



FIG. 45. Stem of the umbrella-liverwort, showing the little cups 

 with bodies inside, which are employed by the plant for pur- 

 poses of propagation. After Atkinson. 



