FLORIDE^E. 



[ 266 ] 



FLORIDE.E. 



The general external appearance of the 

 Red Sea-weeds is very varied. Sometimes 

 the fronds are like little leafless bushes; 

 at others they form broad laminae ; some- 

 times the lower part is stalk-like, and the 

 upper parts spread into leaf-like lobes. In 

 Delesseria we have a close imitation of a 

 regularly formed leaf of one of the higher 

 plants. The leaf-like forms are either sim- 

 ple, lobed, or exquisitely pinnate or fea- 

 thered, and the Rhodosperms of warmer 

 climates exhibit most elegantly reticulated 

 fronds. Some of these plants deposit car- 

 bonate of lime in their tissues in such quan- 

 tity that they become quite stony, so that the 

 vegetable form alone remaining, they are com- 

 monly mistaken for true corals (see CORAL). 

 By placing these corallines and nullipores in 

 vinegar or dilute hydrochloric acid, the lime 

 is removed, and the cellular vegetable orga- 

 nization may be recognized. The tropical 

 forms of the corallines are far more varied 

 and beautiful than our own. 



The fructification of these plants, like that 

 of the other Algae, is as yet but imperfectly 

 known. We find on them three distinct 

 forms of what appear certainly to be. repro- 

 ductive structures, but their relative and 

 special physiological values have still to be 

 ascertained. The three kinds of structure 

 known are called, 1, tetraspores ; 2, spores ; 

 3, anther ozoids, or by some, spermatozoids. 



1. The tetraspores. The structures known 

 under this name are of similar organization 

 throughout this order ; they consist of an 

 oblong or globular external cell or sac (peri- 

 spore), at first filled with granular contents, 

 which contents subsequently separate into 

 four portions, called sporules, either by three 

 transverse fissures (fig. 262) ; by two fis- 



Fig. 252. 



Rhynchococcus coronopifolius. 



Section of the frond with tetraspores. 



Magn. 200 diams. 



sures at right angles, cutting them into 

 quarters like an orange; or by tri-radiate 



fissures which part them into the 'tetra- 

 hedraP group (fig. 253) so often found in the 

 division of spore- and pollen-cells ; the last 

 two occur in the spherical tetraspores. The 



Fig. 253. 



Fig. 254. 



Hildenbrandtia san- 



Ptilota plumosa. 



Section of frond with tetraspores. 

 Magn. 200 diams. 



tetraspores are rarely found collected in any 

 capsular structure, but in the Corallines (fig. 

 141), and in some few foreign genera, they 

 are grouped in hollow 

 cases (conceptacles, fig. 

 254). In many instances, 

 however, they are found 

 in pod-like bodies (stichi- 

 dia, fig. 1 60), either formed 

 by metamorphosis of por- 

 tions of the lobes or lobules 

 of the frond (Plocamium), 

 or arising independently 

 on it. In others the tetra- 

 spores are naked (Calli- 

 thammon), scattered over section ofTclcepta- 



the Sides Or fixed at the cle containing tetra- 



tips of the branches. In 8 P res - 

 the majority of cases, how- Ma & n ' 50 diams - 

 ever, these bodies are immersed in the sub- 

 stance of the lobes or lobules, not evident 

 externally except by the darker colour of the 

 frond at the point where they are collected; 

 a lens is then required for their detection ; 

 they here appear to be formed either of the 

 cells of the surface or of others immediately 

 subjacent. Harvey and Thwaites regard 

 these bodies as gemmules or gonidia. De- 

 caisne, J. Agardh, and most of the other 

 leading Algologists regard them as true 

 spores. 



2. The spores are simpler structures than 

 the tetraspores, but mostly occupy a more 

 important position. They are never scattered 



