96 BOTANY. 



matter, is combined in such form as to make it available for the food of 

 other organisms. 



The marginal cells of the leaf are narrow, and some of them prolonged 

 into teeth. 



A cross-section of the stem (63, E) shows on the outside a single row of 

 epidermal cells, then larger chlorophyll-bearing cells, and in the centre a 

 group of very delicate, small, colorless cells, which in longitudinal section 

 are seen to be elongated, and similar to those forming the midrib of the 

 leaf. These cells probably serve for conducting fluids, much as the 

 similar but more perfectly developed bundles of cells (fibre-vascular 

 bundles) found in the stems and leaves of the higher plants. 



The root hairs, fastening the plant to the ground, are rows of cells with 

 brown walls and oblique partitions. They often merge insensibly into the 

 green filaments (protonema) already noticed. These latter have usually 

 colorless walls, and more numerous chloroplasts, looking very much like 

 a delicate specimen of Cladophora or some similar alga. If a sufficient 

 number of these filaments is examined, some of them will probably show 

 young moss plants growing from them (Fig. 63, A, &), and with a little 

 patience the leafy plant can be traced back to a little bud originating as 

 a branch of the filament. Its diameter is at first scarcely greater than 

 that of the filament, but a series of walls, close together, are formed, so 

 placed as to cut off a pyramidal cell at the top, forming the apical cell of 

 the young moss plant. This apical cell has the form of a three-sided 

 pyramid with the base upward. From it are developed three series of 

 cells, cut off in succession from the three sides, and from these cells are 

 derived all the tissues of the plant which soon becomes of sufficient size 

 to be easily recognizable. 



The protonemal filaments may be made to grow from almost any part 

 of the plant by keeping it moist, but grow most abundantly from the 

 base of the stem. 



The sexual organs are much like those of the liverworts and are borne 

 at the apex of the stems. 



The antheridia (Figs. 59, 60) are club-shaped bodies with a short stalk. 

 The upper part consists of a single layer of large chlorophyll-bearing cells, 

 enclosing a mass of very small, nearly cubical, colorless, sperm cells each 

 of which contains an excessively small spermatozoid. 



The young antheridium has an apical cell giving rise to two series of 

 segments (Fig. 60, A), which in the earlier stages are very plainly marked. 



When ripe the chlorophyll in the outer cells changes color, becoming 

 red, and if a few such antheridia from a plant that has been kept rather 

 dry for a day or two, are teased out in a drop of water, they will quickly 



