Minnesota Plant Life. 139 



rating them from the floor of the cup in which they are pro- 

 duced may be regarded as a special improvement of the dying- 

 away processes which served to separate the unmodified larger 

 branches. The wall of the cup may be considered to be a pro- 

 tective layer of cells originating in earlier forms as a mere collar 

 or ring- and perfected in the umbrella-liverwort into the little cup 

 or vase. Such small cups with their inclosed propagative bod- 

 ies are the result of considerable improvement over earlier and 

 cruder devices. In a liverwort known as the crescent-cup liver- 

 wort, the cup in which the gemmae occur is not circular in out- 

 line but is shaped like a crescent moon. Most liverworts do 

 not produce such cups with gemmae growing from their bot- 

 toms, but are dependent rather upon their reproductive pro- 

 cesses or upon the crude type of propagation in which ordinary 

 branches separate from each other. 



The liverworts which have been mentioned are related more 

 or less closely to each other. They fall naturally into two 

 series, a lower, in which the capsule has no stalk and a higher, 

 in wdiich very short stalks are developed that do not, however, 

 elongate to any considerable degree in any of the species. 



Horned liverworts. Quite a different kind is the horned 

 liverw^ort, plants of which w-ithout doubt occur in all sections 

 of Minnesota, but have been collected in but one or two local- 

 ities. The sexual plant is a flat, somewhat irregular-shaped, 

 green, prostrate stem devoid of leaves. It lies upon decaying 

 timber or mud and forms circles w-hich have not the bright, 

 fresh green color of the mud-liverwort but are of a duller and 

 darker hue. From the upper side of the plant-body spring 

 slender horn-like projections which may become an inch or 

 more in height. These horns are the capsular fruit-bodies of 

 the plant and are developed from eggs produced in egg-organs 

 imbedded in the upper surface of the flat green stem. It is a 

 peculiarity of ^he capsular plant in this kind of liverw'ort that 

 it never fully matures. It consists of a somewhat bulbous foot 

 W'hich is inclosed in the green prostrate stem and above the 

 region of the foot are layers of cells which continue to divide, 

 constantly forming new capsular tissue, so that the capsule may 

 be said to grow from the base. The capsule consists of a wall. 



