xiv.] 



201 



Fucus. C shows the position of the Conceptacles, 



which contain Sporangia, and P denotes the pores or 



openings of the Conceptacles. In fig. 150 one of 



these Conceptacles is enlarged. 



O is the external orifice (P in 



fig. 149), P the perispores or 



sporangia. In some species the 



Antheridia are contained within 



the same conceptacle as the 



perispores ; in others they are 



contained in separate concep- 



tacles on the same or other plants. They consist of 



ovoid sacs containing two Spennatozoids with cilia. 



When set free they enter the conceptacle by its 



external orifice or pore, attach themselves to a 



perispore, penetrate one of the spores contained 



therein, and by thus mingling their protoplasms, 



fertilisation of the spore is effected. 



Algologists divide this group of plants into five 

 subdivisions, as follows : 



1. Olive-coloured seaweeds -(MelanospermecB). 



2. Rose-coloured seaweeds (Rliodospermece}. 



3. Green-coloured seaweeds (Chlorospermece). 



4. Brittleworts (Diatomacece). 



5. Vol voces ( Volvocinece). 



The first of these (Melanospennecf] comprises the 

 various species of Fucus and Laminaria so plentiful 

 on all our coasts. Every visitor to the seaside must 

 be familiar with several species of Fucns, long lines 

 of which are left by the receding tide. Who has 

 not turned over quantities of this leathery jetsam to 

 find the tiny crabs which seek shelter beneath it, 



