DEVELOPMENT OF PLANTS 261 



phyll, while the inner cells divide repeatedly and become very 

 numerous with dense granular contents (Fig. 181, D). Each of 

 the latter cells produces a single male gamete that is motile by 

 means of two cilia (Fig. 181, £). This complex gametangium is 

 suggestive of the structure we have seen in Ectocarpus (Fig. 119, 

 B) . The male gametangium is commonly called the antheridium, 

 and the male gametes are often termed sperms or antherozoids. 

 The gametes are discharged from the antheridium owing to the 

 absorption of water by the walls of the cells in the upper portion of 

 the antheridium which become mucilaginous at maturity and ex- 

 panding, rupture this region of the antheridium, thus permitting 

 the discharge of its contents. The walls of the gamete producing 

 cells also become mucilaginous and by the absorption of moisture 

 they may assist in the extrusion of the gametes. The pressure of 

 the surrounding tissues upon the antheridium is also an important 

 factor in this discharge. The mucilaginous mass that is extruded 

 from the antheridium in this manner, rapidly dissolves in the 

 water and sets free the male gametes or sperms. The female 

 gametangium is also quite different from the single-celled game- 

 tangia which we have noticed among the algae and fungi. It 

 originates as in the case of the antheridium, but develops into a 

 flask-shaped body, consisting of a long neck of several rows of 

 cells surrounding a central row, called the canal cells, and an en- 

 larged basal region in which is developed the female gamete (Fig. 

 182). The female gametangium is commonly known as the arche- 

 gonium and the female gamete is sometimes called the oosphere 

 or egg. The female gamete presents essentially the same char- 

 acteristics as seen in many of the algae, as Vaucheria, Oedogonium, 

 etc., but it is surrounded by a jacket of cells which constitutes the 

 basal portion of the archegonium instead of being contained in 

 a single cell. Possibly the archegonium has come about from a 

 multicellular gametangium as seen in the brown algae, owing to 

 the sterilization of all but one of the cells. Archegonia, with 

 two or more gamete-like cells, are sometimes found in the mosses 

 and ferns and there is evidence tending to show that the primitive 

 gametangia contained both male and female gametes. As soon 

 as the female gamete is formed, the apical or lip cells of the neck 



