264 INTRODUCTION TO BOTANY 



In moist and shady places protonema may grow until great 

 mats are formed upon the soil, old logs, etc., and in these 

 places the alga-like protonema may live for several years. 



At times some of the protonemal cells produce outgrowths 

 which divide by oblique walls and form buds (fig. 203, B and 6). 

 The buds may become dormant and lie for months or even 

 longer, and then continue to grow ; or there may be no resting 

 period. When they grow, the outermost cells produce leaves, 

 the central ones become the stem, and from the lower ones the 

 root- like hairs (rhizoids) grow. The rhizoids descend into the 

 soil or other substance below the plant, and the leaves and 

 stem rise into the air. The buds, therefore, which grow from 

 the protonema are the beginnings of the leafy moss plant. 



250. Sexual and asexual reproduction in the moss. At the 

 tip of the stem of the leafy plant, more or less inclosed by 

 the leaves, the sex organs of the moss develop. These are of 

 two kinds, and with them there are usually taller sterile fila- 

 ments, which bear chlorophyll and may serve to protect the 

 sex organs. In some kinds of mosses only one kind of sex 

 organ is borne on a single plant, while in other kinds both 

 are produced on the same plant at the same time. Neither 

 can be studied without magnification, although the male sex 

 organs may sometimes be detected without a lens. 



The archegonium^ the female sex organ, is similar in func- 

 tion to the oogonium in Vaucheria. It is flask-like and has 

 an elongated neck (fig. 204, Z>). In the swollen part of the 

 archegonium the egg is formed. When the egg is mature, the 

 central cells of the neck become gelatinous, and the end of 

 the neck opens so that there is a passageway through the neck 

 down to the egg. The male sex organ, the antheridium, is 

 club-shaped (fig. 204, ^4), being attached by its smaller end 

 to the tip of the plant stem. When the antheridium opens, 

 its thousands of sperms are set free. The sperms swim with 

 great activity, and some of them may come into the vicinity 

 of the neck of the archegonium. One or more make their way 

 down through the gelatinous neck of the archegonium to the 



