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 Hepaticse. 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 
