CONFERVOIDE^ HETEROGAMY. 123 



being branched, and in having each branch terminated by 

 a slender, tapering, colourless spine, with a swollen base. 



In the genus Coleochcde, although the chlorophyll is 

 bright green, and not masked by the presence of a colouring 

 matter, there is a close approach to the mode of fertilization 

 characteristic of the Floridece or red seaweeds ; but the 

 members of the present genus differ in having motile 

 antherozoids. 



The vegetative part resembles a minute plate or cushion 

 attached to aquatic plants, and consists of dichotomously 

 branched filaments of cells radiating from a centre in one 

 plane ; consequently the plant grows peripherally, owing to 

 the increase in length of its component filaments at the tips. 

 In some species the spreading filaments produce branches 

 that grow erect in a compact manner, forming a cushion- 

 like tuft. Some of the cells of the thallus form a pro- 

 tuberance on the free upper surface, which elongates for 

 some distance and then splits at the apex, and from out of 

 the split apex a long, slender, colourless spine protrudes, as 

 from a sheath. 



Asexual reproduction takes place by means of biciliated 

 zoospores, which escape from the mother-cell or antheridium 

 through a round hole which appears in the wall. 



Sexual reproduction is brought about by the fertilization 

 of an oosphere by ciliated antherozoids, but not directly as 

 in the preceding groups, but through the agency of a 

 trichogyne, or outgrowth of the oogonium. The oogonium 

 is formed from the terminal cell of a branch which increases 

 in size, and at the same time elongates at its apex into a 

 long slender tube or trichogyne, which opens at its point 

 and exudes a drop of mucilage. The protoplasm of the 

 swollen part of the oogonium which contains chlorophyll 



