CHAPTER XI.- THE BRYOPHYTA. 337 



cells which must be regarded as anticipating the fibro-vascular 

 bundles of the higher plants, though true vessels are never 

 developed. 



Mosses differ from most of the higher plants in their branch- 

 ing. The thalloid forms mostly branch dichotomously, and the 

 branches of the foliose forms do not spring from the leaf-axils, 

 but from the side of the leaf, or from a point below it. The 

 stems increase in length by means of a single terminal cell, and 

 in many cases the plants continue to grow at the apex, while 

 dying away at the base. 



The organs of reproduction consist of antheridia and arche- 

 gonia. These are sometimes borne solitary on the stem or thal- 

 lus, but more commonly in groups ; sometimes both kinds of 

 organs in the same group, sometimes the different kinds in distinct 

 groups. They are often closely associated with hair-like bodies, 

 called paraphyses, and are not infrequently surrounded with 

 slightly modified leaves, called the perichtztium or the perigynium. 



The antheridia are short-stalked, multicellular bodies, spher- 

 ical, oblong, ovate or club-shaped in form, and produce in their 

 interior cells multitudes of minute, slender, spirally-coiled, bi- 

 ciliated antherozoids. The latter are thicker at one end, and it 

 is to the opposite end that the cilia are attached. (See Figs. 543 

 and 544.) 



The archegonia are flask-shaped, multicellular bodies, with a 

 narrow, elongated neck, and a relatively thick, rounded base. 

 They possess at first an axial row of cells, the one in the dilated 

 base being of larger size than the rest, and constituting the germ- 

 cell. Later, the axial cells of the neck dissolve into mucilage, 

 through which the antherozoids penetrate to the germ-cell. The 

 former are discharged from the antheridia when moisture is 

 present, and it is through the medium of the water that they find 

 their way to the archegonia. (See Fig. 545). 



The fertilization thus effected initiates an important series 

 of changes resulting in the production of the plant of the asexual 

 generation, very different in appearance from the sexual plant, 

 but growing up in contact with it, and technically called the sporo- 

 goniutn. The process of development is as follows : The fertil- 

 ized germ-cell, still enclosed within the archegonium, divides 

 repeatedly in different directions, and the lower portion of the 



