IOWA ACADEMY OF SCIENCES. 155 



After the egg-cell or oOsphere, which is produced within the 

 archegonium, is fertilized by the motile antherozoid cell from 

 the antheridium, it begins at once to divide, and develops 

 rapidly into a capsule and stalk. During this growth the lower 

 portion of the stalk is pressed downward into the end of the 

 stem from which the nourishment for the asexual phase of the 

 plant existence is derived, as in the case of a parasite. The grow- 

 ing embryo soon ruptures the wall of the archegonium near the 

 base, the upper part of which is carried up on top of the capsule, 

 where it is called the calyptra. This stalked capsule or 

 sporogonium, constitutes the asexual generation. It is less con- 

 spicuous than the sexual phase, and is developed exclusively for 

 the production of the spores. 



Mosses may be distinguished from the liverworts by the 

 fact that in the sexual generation of the former, protonemal 

 filaments are always well developed, on which the leafy axis is 

 produced which shows no sign of dorsi- ventral structure. 



The rhizoids of mosses are usually made up of a row of cells 

 instead of a single cell as in the Hepaticce. The mature cap 

 sule of the mosses opens by a special lid, the operculum, which 

 is covered by the calyptra. The columella is also present, at 

 least in the early stages of the development of the capsule, 

 and the mouth of the capsule usually shows a well developed 

 peristome, consisting of one or more rows of minute teeth. 

 Elaters, which are produced by the liverworts, are absent in 

 the mosses. 



Mosses grow in shallow water, on the ground in swamps and 

 ditches, in open fields and in shady places, on decayed logs and 

 stumps in the woods, on rocky ledges and loose stones along 

 streams, and on the bark of living trees. They vary in 

 size from the small forms, a few millimeters in length, to large, 

 floating or creeping plants, which attain a length of several 

 inches. 



At no season of the year will the collector fail to be 

 rewarded in his search for mosses. Some fruit in early spring, 

 some in midsummer, some in the late autumn, and some may be 

 found in fine fruit during the warmer periods of midwinter. 



The following list of seventy-eight species and varieties 

 represents but an incomplete collection from a few points in the 

 state. It is given with the hope that it may bring more to the 

 notice of our collectors a group of plants that has hitherto been 

 undeservedly neglected. In its preparation, the writer is 



