MOBPHOLOGY OF KEPEODUCTIVE ORGANS 227 



The Gametangia. 



As the structures in which the spores are produced are called 

 generally sporangia, so the term gainetangia may be applied to 

 those bodies in which the gametes are formed. 



In isogamous plants the gametangia, like the gametes, are 

 indistinguishable from each other. In the plants mentioned 

 above, the gametangium is a single cell of the filament, showing 

 no difference from any of the other cells. Sometimes the contents 

 of the gametangium divide up into a large number of gametes 

 (fig. 485) ; in other oases the whole of its protoplasm becomes 

 rounded up into a single one (fig. 486). 



A similar absence of differentiation marks the gametangia 

 of some of the heterogamous forms. Usually, however, those 

 which give rise to antherozoids are very different from those 

 which produce oospheres. The former are generally called 

 aniheridia, the latter oogonia or archegonia, the last named 

 being the most complex in structure. 



The antheridium is usually a somewhat ovoid body, composed 

 of several cells ; it is often stalked, and in some cases furnished 

 with a kind of lid. In Chara it is globular and of very complex 

 structure. In the lower plants it is imioeUular in many eases, 

 and may then only produce a single antherozoid. In certain of 

 the Fungi it takes the form of a somewhat club-shaped branch 

 of the mycelium, and is called a pollinodium (fig. 489, an). 

 In Salvinia it is the apex of a tube-like outgrowth from the 

 microspore. In the Augiosperms, where again the gametophyte 

 springing from the microspore is a long tubular outgrowth, the 

 antheridium is not differentiated. 



The gametangium producing the oospheres may be either an 

 oogonium or an archegonium. The former is unicellular, and 

 sometimes, as in, Volvox, hardly distinguishable from any other 

 cell of the plant. In other cases it is an ovoid or spherical body, 

 often mounted on a stalls. It usually produces one oosphere, and 

 this often remains in it till fertilisation. In Fucus (figs. 493-496) 

 it contains eight oospheres, which are released by a rupture of the 

 oogonium wall, and come into contact with the antherozoids 

 after their escape. In Chara ( fig. 490, s) the oogonium is sur- 

 rounded by an investment of cells which enclose it, except at 

 the apex. 



In plants above the Thallophytes the female gametangium is 

 an archegonium. It is multicellular, and consists of a swollen 



Q2 



