208 PRACTICAL BOTANY 



spermatozoids separate, as actively motile bodies of elongated 

 pear-like form. Observe their movements. 



To a drop of water containing motile spermatozoids add a 

 little iodine solution, put on a cover-slip, and examine under a 

 high power : the two cilia may be observed on each sperma- 

 tozoid attached laterally. 



Mount in a drop of fresh sea- water some of the darker-coloured 

 exudation from the female conceptacles, and examine under a 

 high power : observe the numerous oogonia, with the pedicel 

 often attached : note the thick limiting wall, consisting ob- 

 viously of two layers, an outer (extine) more highly refractive, 

 the inner (intine) having the characteristic optical appearance of a 

 mucilaginous wall : a shallow pit is to be seen on the wall ad- 

 joining the pedicel. The contents will be seen in most cases or 

 in all to be divided, as above described, into eight cells the 

 ova. Some of the oogonia will be seen to burst on exposure to 

 the water : watch the process and note the following stages 



1. A slight convexity appears usually near the apex, the 

 extine having there ruptured, and the intine beginning to 

 protrude. 



2. The rupture extends, and the extine gradually shrivels back 

 so as to leave the intine fully exposed, though it usually remains 

 still attached to the extine at the base. 



3. The intine swells, and ultimately loses its contour at the 

 apex, and the oospheres, which had meanwhile separated and 

 rounded off, escape into the water as eight naked, non-motile 

 spheres of dark granular protoplasm : in each may be recognized 

 a central clearer area the nucleus. 



Into a drop of sea- water in which are free and mature ova, 

 introduce a small number of mature spermatozoids, and watch 

 their movements : they may be seen to approach the ova, to 

 apply themselves closely to their surface, along which they 

 creep : if present in considerable numbers, they give to the ova 

 an irregular rotating movement. 



XII. On stones, in districts where Fucus abounds, there may be 

 found early in summer olive-brown velvety patches : on examining 

 these with a lens, small club-shaped bodies may be distinguished, 

 attached by their narrower end to the substratum, and with 



