ALG.-E 191 



Landsborough -Popular Hist, of British Seaweeds, 1851. 



Pringsheim -Ueber Befruchtung u. Keimung der Algen, 1855. 



Gray British Seaweeds, 1867. 



Wood Fresh-water Algae of North America, 1873. 



Bornet & Thuret Notes Algologiques, 1876 80. 



Falkenberg Die Algen, in Schenk's Handbuch der Botanik, vol. ii., 1881. 



Hauck Die Meeresalgen, in Rabenhorst'sKryptogamen-Flora Deutschland, 1883-85. 



Schmitz Die Chromatophoren der Algen, 1882; andjourn. Micr. Soc. , 1883, p. 405. 



Cooke British Fresh-water Algae, 1884. 



Gay Bull. Soc. Bot. France, 1886, Sess. Extraord., p. 21. 



Bennett -Journ. Linn. Soc., xxiv., 1887, p. 49. 



Wolle Fresh-water Algae of the United States, 1887. 



Wille (Resting-spores) Pringsheim's Jahrb. wiss. Bot., 1887, p. 492. 



Stroemfelt (Attachment-disc) Bot. Centralbl., xxxiii., 1888, pp. 381 & 395. 



Class X.--Florideae. 



This large family known also as Rhodosporeae and Rhodospermese 

 exhibits the highest type among Algae in the mode of sexual repro- 

 duction, and also possibly in the development of the vegetative organs. 

 It consists almost entirely of seaweeds, including all the red and purple 

 kinds. A few species only, belonging to the genera Hildenbrandtia 

 (Nard.), Batrachospermum (Bory), Lemanea (Bory), Bangia (Lyng.), 

 and a few others, grow in fresh water. Some of these are green, but the 

 great majority of the Florideae are of a bright red colour, varying with 

 purple, brown, yellowish, or dirty white. The 'fronds' do not attain 

 nearly the size of those of the Fucaceae and Laminariaceae, but they are 

 often of delicate texture and finely divided, rendering them the most 

 beautiful of our seaweeds. 



The thallus varies within very wide limits in its degree of develop- 

 ment. In a few genera, such as Callithamnion (Lyng.), it consists of 

 distinct filaments of cells which are almost always branched ; in others, 

 as Porphyra (Ag.), Hildenbrandtia, and Cruoria (Fr.), of a flat plate of 

 cells, composed of only a single or of several layers ; in the fresh- water 

 genus Batrachospermum, of an axis with beautifully regular whorls of 

 branches ; while in most seaweeds it constitutes a massive parenchyme, 

 or the filaments are held together by a more or less dense gelatinous 

 envelope. Growth takes place, in the majority of cases, by means of a 

 single apical cell, but this is often followed by a strong intercalary 

 growth. The apical cell is not three-sided, as in Vascular Cryptogams, 

 but is either wedge-shaped, dividing by walls which incline alternately to 

 the right and left, or it divides by nearly parallel walls. In some forms, 

 however, especially the prostrate Melobesiaceae and Squamariaceae, and 



