FLORIDE/E. 129 



the whole more general in the Florideae than the sexual 

 method ; nevertheless it is absent in some genera, as Le7nanea 

 and Nemalion. Tetraspores are most frequently formed in 

 fours in a mother-cell or tetrasporangium, and originate in 

 different ways, the most usual being by simultaneous parti- 

 tion into four tetrahedra, which remain for some time in 

 organic continuity by narrow necks of protoplasm ; in other 

 cases the tetraspores are formed by successive bipartitions 

 in two planes at right angles to each other, thus forming 

 four quadrants of a sphere ; finally the four tetraspores are 

 arranged in a single row, as in the genus Corallina. The 

 tetrasporangia occupy different positions in the various 

 genera, sometimes immersed in the substance of the thallus, 

 and scattered or collected in sori or dense patches, or borne 

 on modified branchlets called stichidia. In the genus 

 Corallina and its allies the tetrasporangia are developed 

 within highly-specialized conceptacles. On germination 

 the stationary tetragonidia may give origin to either sexual 

 or asexual plants, but sexual and asexual organs of repro- 

 duction are not produced by the same plant. 



In the sexual mode of reproduction the female organ 

 exhibits in the various genera a sequence from a simple 

 type to one of considerable complexity, but in every instance 

 fertilization is indirect, the naked, motionless antherozoids 

 or poUinoids becoming attached to the upper portion of a 

 trichogyne, where they develop a cell-wall. At the point of 

 contact the cell-wall of both poUinoid and trichogyne is 

 dissolved, and the contents of the former pass down the 

 trichogyne, and effect fertilization, after which the latter 

 disappears. The trichogyne is always closed at the apex. 



In the present order the female organ is called a car- 

 pogonium, a. structure homologous with the oogonium of 



K 



