FUCUS. 59 



a solution of Tidman's sea salt of proper strength, in 

 place of fresh sea-water. 



If specimens of Fucus serratus be kept exposed to 

 the air for some hours (the period of one tide will 

 suffice), an exudation may be observed from the ostioles 

 of some of the conceptacles : on male plants it will 

 be of an orange colour, on female plants of a dark olive- 

 green. 



Taking first the male, mount a small quantity of the 

 orange exudation in a drop of fresh sea-water, and 

 examine it under a high power : it will be found to 

 consist of numerous antheridial cells, separated from 

 the hairs which bore them : they will be seen to be 

 bursting, and setting free their contents, and the 

 following stages of the process are to be noted 



1. The antheridial cell is completely closed, the 

 contents are already divided into numerous elongated 

 bodies (said to be sixty-four in number), each having 

 one or sometimes two brightly orange-coloured globules 

 (chromatophores) : these are the antherozoids, 

 and they may be seen to be in motion before the 

 antheridium bursts. 



2. The wall of the antheridium consists of two layers, 

 the outer more firm layer (extine) and the inner 

 mucilaginous layer (inline) : observe the extine to 

 burst at one end, usually at the apex, and the contents 

 inclosed in the intine escape from it. 



3. The intine gradually swells, loses its contour, and 

 the antherozoids separate, as actively motile bodies of 

 elongated pear-like form. Observe their movements. 



To a drop of water containing motile antherozoids 

 add a little iodine solution, put on a cover-slip, and 



