112 



MORPHOLOGY 



The leaves at first have similar cells, but later there is a striking differentiation, 

 certain of the cells becoming enlarged, hyaline, and perforate (figs. 244, 245). 

 It is this abundance of hyaline cells and paucity of 

 chlorophyll-containing cells that give a pallid look to the 

 leaves. 



The axis of the leafy branch is differentiated into three 

 regions: (i) a cortex of empty and perforate cells, like the 

 hyaline cells of the leaf; (2) a cylinder of elongated cells 

 with thick walls and small caliber (prosenchyma) ; and 

 (3) a pithlike axis. 



There are no special structures for vegetative 

 multiplication, but great masses of individuals are 

 formed by the indefinite growth and branching 

 above, accompanied by dying off below. 

 FIG. 246. Sphag- Antheridium. The antheridia occur on special 



num: terminal cluster , , , f , , , ,. . . 



of antheridial branches. densel 7 Ieaf 7 branches resembling small catkins 

 (fig. 246). The leaves also usually differ in color 

 from the ordinary leaves, and in the axil of each there is a solitary 

 globular and long-stalked antheridium (fig. 247), just as in Porella 

 (seep. 104). These antheridia 

 develop by means of an apical 

 cell with two cutting faces, the 

 lower segments forming the 

 stalk, and the upper segments 

 forming the capsule, which is 

 initiated by a series of peri- 

 clinal walls that cut off the 

 peripheral wall layer from a 

 central spermatogenous group 

 of cells. The antheridium 

 opens by irregular lobes and 

 discharges the two or three- 

 coiled biciliate sperms. 



Archegonium. The arche- FIG. 247. Sphagnum: an antheridium aris- 



gonia OCCUr at the apex of ^ n branch between two leaves showing the 



G slender stalk and the globular head; the latter 



short branches, at the top of consisting of a wall (a single layer of cells) in- 



the plant (figs. 248, 249). vesting a mass of spermatogenous cells (in 



They are stalked and free, ^ich blocking can be distinguished). 



and develop as in the acrogynous Jungermanniales, the archegonium 



initials being segments of the apical cell, which itself finally becomes an 



