148 Minnesota Plant Life. 



which the microscopic organs of sex arise. The sperm-pro- 

 ducing organs are spherical with long slender stalks and arise 

 in the axils of the leaves. The egg-producing organs are 

 formed upon the tips of certain branches and in each, as is the 

 rule, a single egg is produced, and this when fecundated may 

 segment into an embryo which in time matures into the cap- 

 sular plant of its species. 



Granite-mosses. Another group somewhat related to the 

 last are the granite-mosses representatives of which may pos- 

 sibly grow upon granitic rocks near Carlton peak and along the 

 north shore of Lake Superior. They are small black tufted 

 plants distinguished from all other mosses by the longitudinal 

 splitting of the capsular plant by four lateral slits which do not 

 meet either at the top or bottom of the capsule. When dry the 

 capsule seems to shorten and the slits are thus opened so that 

 spores may sift out at the sides. The valves of such capsules 

 are somewhat sensitive to moisture and when conditions are 

 unfavorable for the distribution of spores the slits are likely to 

 remain closed. 



In both of the families of mosses which have been described 

 there is a central column of sterile cells giving strength to the 

 capsule, and the spore-mother-cells are developed in the region 

 between the column and the wall. In neither of the families does 

 the column run clear through the capsule, but the spore-mother- 

 cell area extends over its top like a cup set over a mould. Quite 

 the same general structure of capsule was observed in the horned 

 liverworts except that in those plants the growth of the capsule 

 was not definitely terminated but continued from the base. In 

 peat- and in granite-mosses the growth of the capsule is termi- 

 nated after a time and it then contains no more vegetative cells 

 capable of further division. Therefore, the capsule of peat- and 

 of granite-mosses may be regarded as built on the general plan of 

 a horned liverwort capsule, except that the power of continuous 

 development is lost. It might be mentioned here for the sake of 

 clearness that the club-moss spore-bearing plant is also supposed 

 to be an improvement over the horned liverwort type. But in 

 club-mosses and ferns a power of continuous growth is retained. 



Higher mosses. A peculiar little group of mosses, very 

 tiny and insignificant in appearance, form reduced capsules in 



