128 Minnesota Plant Life. 



stance of the egg, and immediately the egg forms around itself 

 a membrane by which the ingress of other sperms is prevented. 

 Such an egg is said to be fecundated and in a short time it di- 

 vides by a cross-partition — in a direction perpendicular to the 

 long axis of the bottle in all mosses and liverworts with the 

 exception of the horned liverworts, in which the first partition 

 is parallel with this axis. The egg now consists of two cells 

 and this two-celled body is reasonably to be considered as the 

 first-stage of the embryo-plant of the next generation. Such 

 an embryo normally develops into a spore-producing capsule, 

 provided in some species with a long and slender stalk, but in 

 other varieties having only a short nub of sterile cells at the 

 base. In the lowest family of the liverworts there is no stalk 

 of any kind, but the entire matured product of the embryo be- 

 comes a little spherical capsule imbedded in the tissue of the 

 sexual plant. Whatever may be its structure the capsule finally 

 l^roduces spores. The function of a moss or liverwort capsule 

 may be described in brief as the production of as nuniy and as 

 certainly gerniinablc spores as possible. In high types of moss- 

 fruits the number of spores rises into the thousands, while in the 

 lowest forms of liverwort-fruits, the number of spores runs from 

 sixteen to sixty four. 



What is meant by "alternating generations." It is evident 

 that there exist, in the moss life-history, two plants alternating 

 with each other. One, the sexual plant, has two phases, the im- 

 mature or first-stage and the mature or second-stage. The first- 

 stage does not, except in one kind of moss, produce the organs 

 of sex, and in this peculiar moss it is not the egg-organs but 

 the spermaries that are formed upon it. Therefore, one may 

 describe the second-stage of the moss sexual plant as a repro- 

 ductive branch of the first-stage. The other, the capsular plant of 

 the life-history, is entirely devoid of sex, but is a spore-produc- 

 ing organism. This serves to illustrate one of the very remark- 

 able differences between higher plants and higher animals. In 

 higher animals a fecundated egg develops into an organism like 

 one of those that cooperated in the production of the fecundated 

 egg, thus the egg of a fowl develops into a fowl, and the egg 

 of a fish into a fish ; but the egg of the moss does not develop 

 into an organism like the ones that cooperated in its produc- 



