ALGjE 191 



Landsborough - Popular Hist, of British Seaweeds, 1 85 1. 



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



Gray — British Seaweeds, 1867. 



Wood — Fresh-water Algje 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 Algje, 1884. 



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



Bennett— Journ. Linn. Soc, xxiv. , 1S87, p. 49. 



AVolle — Fresh-water Algse 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 Rhodosporcce and Rhodospermeae 

 — exhibits the highest type among Alg^ 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), I.emanea (Bon,-), Bangia (Lyng.), 

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

 great majority of the Floride^e 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 Fucaceje and Laminariaceas, 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.), Plildenbrandtia, 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 parenchyma, 

 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 Cr}'ptogams, 

 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 Squamariace^, and 



