140 Minnesota Plant Life. 



more than one layer of cells in thickness, and a central column 

 of cells giving strength and support to the whole structure. 

 Between the central column and the wall is the area where the 

 spherical spore-mother-cells develop. Each of these is capable 

 of forming its group of four spores. Mixed with the spore- 

 mother-cells are some rather crude elaters which play their part 

 in the distribution of the spores somewhat as did the more 

 mechanically perfect elater-cells in the cone-headed liverwort 

 and its allies. When the capsule of the horned liverwort is 

 ripe, it splits longitudinally through its whole length and the 

 two dry halves twist about each other and about the little col- 

 umn of the centre now exposed as a thread. By the twisting- 

 movement of the two halves of the capsule the distribution of 

 the spores is facilitated. 



This kind of liverwort is extraordinarily interesting to bot- 

 anists because it seems to be a connecting link between the 

 liverworts and the club-mosses. The horned liverwort differs 

 considerably from the cone-headed liverworts, the mud-liver- 

 worts and their allies, in the character of its capsular plant. As 

 will be seen from the description this is of higher structural 

 rank. A greater proportion of its substance is sterilized, that 

 is, not dedicated to the production of spores, while in the um- 

 brella-liverwort the only sterile portion of the plant was the 

 wall and the short stalk or foot. In the horned liverwort there 

 exists in addition, a central column of cells making possible, by 

 the support which it gives, the development of a much larger 

 capsule containing many more spores. Furthermore, with its 

 indeterminate growth the capsule continues and is not com- 

 pleted, as were simpler forms of capsular plants, after a certain 

 definite number of cell divisions. In this capsular plant one ob- 

 serves the first tendency of such an organism to become peren- 

 nial. In all other liverwort capsular plants there is aimed at, 

 in the development, a definite and finished structure, and when 

 the capsule has been once matured there is no further growth. 

 Under such conditions it is not possible for a capsular plant to 

 arise capable of maintaining itself from year to year. The 

 horned liverworts do not really produce perennial capsular 

 plants, but they indicate how in the asexual generation perennial 



