60 PRACTICAL BOTANY. 



examine under a high power : the two cilia may be 

 observed attached laterally. 



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

 darker-coloured exudation from the female con- 

 ceptacles, and examine under a high power: observe 

 the numerous oogonia, with the pedicel cell often 

 attached : note the thick limiting wall, consisting 

 obviously 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 adjoining the pedicel. The 

 contents will be seen in most cases or in all to be 

 divided, as above described, into eight cells the 

 oospheres. 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 recognised a central clearer 

 area the nucleus. 



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

 mature oospheres, introduce a small number of mature 

 antherozoids, and watch their movements: they may 



