252 



FOUKDATIONS OF BOTANT 



In conceptacles of the other kind examine the numerous small 

 sa,c-shaped cells (antheridia). At maturity the contents of each 

 divide to form numerous very minute motile antherozoids, each with 

 two delicate hairs or cilia. Dissect, by picking and by friction under 



cover-glass, a bunch of 

 antheridia and note 

 the branching fila- 

 ments upon which 

 they are borne. 



Make drawings to 

 illustrate the various 

 points of structure. 



295. Number of 

 Antherozoids required 

 for Fertilization. — The 

 bulk of an oosphere 

 has been estimated 

 equal to that of thirty 

 thousand to sixty 

 thousand antherozoids, 

 but apparently an 

 oosphere may be fer- 

 tilized by only one 

 antherozoid. Yet a 

 large mimber swarm 

 around each oosphere 

 after both have 

 escaped from the con- 

 ceptacles, and often 

 their movements are 

 so active as to cause the rotation of the oosphere. The process of 

 fertilization may be discerned in fresh material by squeezing 

 oospheres and antherozoids from their respective conceptacles into 

 a drop of water on a slide. In some species, as Fucus plat^carpus 

 (Fig. 186), antheridia and oogonia are found in the same 

 conceptacle. 



Fig. 186. — Transverse Section of Conceptacle of a 

 Eockweed (JW«s plaiycarpus). (x about 35.) 



h, hairs ; a, antheridia ; o, ocigonia. 



