42 SEAWEEDS 



both within definite conceptacles more or less local- 

 ised on the thallus, the oospheres being enormously 

 greater in volume than the antherozoids. The 

 antherozoids are at most sixty-four in each anther- 

 idium, while the oospheres are typically eight in 

 each oogonium. In particular genera each oogonium 

 develops only one, or two, or four oospheres, but in 

 all the Fucacece that have been examined in this 

 respect the original nucleus of the oogonium always 

 divides into eight daughter-nuclei, of which only 

 those remain effective that are destined to belong to 

 oospheres, while the remainder, in genera possessing 

 one, two, or four oospheres, are rejected. Both an- 

 therozoids and oospheres are extruded from the con- 

 ceptacles, and fertilisation takes place, as in the rest 

 of the Phceophycece, outside the plant. There are no 

 non-sexual spores produced, and with the exception of 

 vegetative propagation by broken off fronds, there 

 is no other kind of reproduction known in Fucacece. 

 It is probable that in the parasitic and much 

 reduced Notheia, of which research has failed to 

 disclose the antheridia, the oospheres remain un- 

 fertilised, and if they reproduce the plant, as is ex- 

 tremely probable, do so parthenogenetically. Of all 

 Algae they show the highest degree of differentiation 

 of parts, and attain the greatest dimensions, with the 

 single exception of the Laminariacece. A consider- 

 able variation, however, occurs among the different 

 genera in the matter of vegetative development, 

 the least of any being exhibited by Notheia. 



The Thallus. The thallus of the Fucacece some- 

 times attains a development and differentiation of 



