FLOR1DEJ]. 83 



Order 2. Helminthocladiaceae. Tetraspores are generally wanting (e.g. in 

 Nemalion) or arise one in each tetrasporangium (e.g. Batrachospermum) and it 

 is only in Liagora that four cruciate tetraspores are formed. Chantransia 

 corymUfera consists of simple, branched cell-rows, and is an independent species. 

 Several other Chantransia- forms, living in fresh water, are "proembryos" of 

 species of the genus Batrachospermum. The germinating carpospore grows out 

 into filaments and forms a so-called proembryo which, if not shaded, attains 

 only a small size, but when growing in shady situations presents a much greater 

 development. These highly developed proembryos have been described as 

 species of Chantransia. The proembryo can reproduce by division, or by tetra- 

 spores which are developed singly in the sporangia; in B. vagum and B. sporu- 

 lans which do not possess fully developed female reproductive organs, the pro- 

 embryos serve almost entirely to reproduce the species. The young Batracho- 

 spermum-plaut arises from the end of an upright filament of the proembryo. 

 The proembryo is generally persistent, and continually produces new Batracho- 

 spermums. These latter bear the sexual reproductive organs and also whorls of 

 branches : the central row of cells is enclosed by cells growing from the base of 

 the whorls of branches, and from these cortical cells secondary proembryos are 

 developed. In this alternation of shoots there is really no alternation of 

 generations, since the proembryo and the shoots with the sexual reproductive 

 organs are parts of the same thallus. 



Several species of Batrachospermum have a bluish-green or verdigris colour. 

 Nemalion multifidum has a brown-red thallus, slightly branched, which is 

 attached to rocks near the water's edge. 



Order 3. Chaetangiaceae. Galaxaura has a thallus thickly incrusted with 

 lime. 



Order 4. Gelidiaceae. Naccaria, Gelidium. 



Sub-Family 2. Gigartinales. The fertilised auxiliary cell grows towards 

 the thallus, to produce the gonimoblasts. Procarpia generally present. 



Order 5. Acrotylaceae. Acrotylus. 



Order 6. Gigartinaceae. Gigartina, Phyllophora, Ahnfeltia; Chondrus 

 crispus, with dark red, dichotomously branched thallus, is common on the 

 coasts of Scandinavia and Great Britain. 



Order 7. Rhodophyllidaceae. Rhodophyllis, Euthora; Cystoclonium pur- 

 purascens is common, and sometimes the ends of its branches may be modified 

 into tendril-like haptera. 



Sub-Family 3. Rhodymeniales. The fertilised auxiliary cell forms the 

 gonimoblast on the side away from the thallus. Procarpia are abundantly 

 produced. 



Order 8. Sphaerococcaceae. Gracilaria. 



Order 9. Rhodymeniacese. Rhodymenia palmata is a common species. 

 Lomentaria, Chylocladia, Plocamium. 



Order 10. Delesseriaceae. Delesseria sanguinca ; D. alata and D. sinuosa 

 are handsome forms which are not uncommon. 



Order 11. Bonnemaisoniaceae. Bonnemaisonia. 



Order 12. Rhodomelaceae. Rhodomela, Odonthalia ; Polysiphonia, of 

 which many species are to be found on the coasts of Great Britain, has a 

 filamentous, richly branched thallus consisting of a central row of cells sur- 



