FLORIDE.^ 



195 



(Lmx.), and a few other genera, the 'frond' becomes densely incrusted 

 by a deposit of calcium carbonate, giving to the so-called 'corallines' 

 the external form and appearance of miniature corals. 



The ordinary non-sexual propagative organs of the Floridese are 

 bright red motionless spores, commonly formed in fours in the mother- 

 cell, and hence known as tetraspores (the sphaerospores of Agardh), and 

 the cell in which they are produced as a tetrasporange. The four spores 

 are sometimes arranged in a row, when they are called zo?iate ; more 

 often as quadrants of a sphere, when they are cruciate : rarely there are 

 only one or two, or occasionally eight. In the Ulvaccce, Lemaneacese, 









Fig. T-]2..—Cro7cania attennata Ag. a, branch (x 40) ; h, apex of branch (x 100) ; c, lower 

 portion of branch with tetrasporanges ( x 100). (After Kiitzing.) 



and in some Nemaliea^ they are altogether wanting. The tetraspores 



(see fig. 231) may be formed in the six following ways : — (i) The 



whole contents of the sporange become a single spore ; (2) the contents 



divide into two equal parts by a transverse wall ; (3) they divide into 



four quadrants by two successive bipartitions ; (4) they divide into four 



tetrahedra by simultaneous quadripartition ; (5) they divide into four 



by three parallel transverse walls ; (6) the contents divide into more 



than four spores. On germination the tetraspores may give birth either 



to sexual or to non-sexual individuals. In the monosiphonous Florideae 



the tetrasporanges are usually formed at the expense of the ultimate 



branchlets. In other forms they are most commonly found scattered 



o 2 



