384 



BOTANY OF THE LIVING PLANT 



to form 64 nuclei, each of which becomes the centre of a spermatozoid. 

 The cytoplasm divides into as many portions, and each is found to 

 contain a red eye-spot beside the nucleus (Fig. 324, 2). The contents 

 slip out when ripe from the ruptured outer wall, as a mass still sur- 

 rounded by the inner wall : this soon deliquesces, and sets them 



FIG. 324. 



Fucus. i, group of antheridia. 2, part of an antheridium showing developed 

 spermatozoids. 3, spermatozoid ; a=eye-spot; = nucleus. 4, Isolated antheridia 

 liberating spermatozoids. 5, ovum surrounded by spermatozoids. 6, section through 

 a fertilised egg; ft=nucleusof egg; s/>=nucleus of sperm; s=spermatozoids: 

 (i, 4, 5 after Thuret ; 2, 3 after Guignard ; 6 after Farmer.) (From Strasburger.) 



free as 64 motile spermatozoids, each with the characters usual for 

 the Brown Seaweeds (4). The oogonia though larger are of the same 

 pattern. Each has at first one nucleus ; but here it divides only 

 to form eight, and the cytoplasm undergoes cleavage into eight large 

 ova. They are also shed in the same way, and round themselves off 

 as non-motile eggs (5). 



A comparison of the antheridium with the oogonium in the Fucaceae shows 

 that they are probably results of differentiation from a common source. When 

 an oogonium is to be formed, a cell of the wall of the conceptacle grows inwards 

 into the cavity, and divides to form a stalk-cell and an oo b onium (Fig. 325, 



