ALGAE. RHODOPHYCEAE. 73 



sluggish oospheres rotating, and this may continue for a half hour. Thuret leaves it 

 uncertain whether spermatozoids penetrate into the oosphere ; the analogy of the 

 phenomena observed by Pringsheim in Vaucheria and Oedogonium, and of the sexual 

 process recently and repeatedly observed, leaves no room for doubt that one or more 

 of the spermatozoids mingle their substance with that of the naked sphere of pro- 

 toplasm which forms the oosphere. Soon after these events the oospore becomes 

 invested with a cell-wall, attaches itself to some object, and without passing through 

 a resting period begins to germinate by elongating and dividing first by a transverse 

 septum ; this is followed by many other divisions, and the cellular body thus formed 

 developes a hyaline root-like organ of attachment at the lower end, while the free 

 thick end (Fig. 45, IV) is the growing apex. The development of a fertile thallus 

 from the oospore has not yet been observed, and therefore the whole cycle of 

 changes in the Fucaceae has not yet been certainly ascertained. 



C. RHODOPHYCEAE OR FLORIDEAE 1 . 



The Florideae or Red Seaweeds, Rhodophyceae or Rhodospermeae, are chiefly 

 distinguished from the two other large series of Algae, the Chlorophyceae and 

 Phaeophyceae, by the mode of their sexual reproduction. In the two latter groups 

 a zygospore or an oospore was produced by the union of one or more male sexual 

 elements with a female ; but the proceeding is different in the Florideae ; in them 

 there is found before fertilisation a unicellular or pluricellular female sexual apparatus, 

 the procarp, which separates into two parts, each with a distinct function ; the one is 

 a receptive apparatus, the Irichogyne, the other is excited by fertilisation to a vegetative 

 process which ends in the production of spores. This part is called the carpogone, 

 and may be composed of one or several carpogenous cells ; the spores produced from 

 it in various ways are known as carpospores, to distinguish them from the asexually 

 produced tetraspores, which are usually formed by division of a mother-cell into 

 four. Fertilisation is effected by passively motile male sexual cells without cilia, the 

 spermatia 2 . 



The variety of forms in the Florideae is great, and the procarp in the different 

 genera varies much in form, structure, and position on the thallus. One of the 

 simplest cases is represented by the genus Nemalion, in which the procarp is uni- 

 cellular (Fig. 49, /, c) ; the much elongated apex (/) in the figure is the trichogyne, the 

 enlarged bulbous lower portion of the procarp is the carpogone (c). The spermatia 



1 Nageli u. Cramer, Pflanzenphysiol. Unters. Zurich, 1855, Heft I ; 1857, Heft IV. Thuret, 

 Recherches sur la fecondation &c. (Ann. d. sc. nat. 1855). Nageli, Neue Algensysteme, 1847 ; Id. in 

 Sitzungsber. der Bayer. Akad. d. Wissenschaft. 1861, vol. II. Bornet et Thuret, Recherches sur la 

 fecondation des Floridees (Entdeckung der Befruchtung) (Ann. d. sc. nat., ser. 5, T. VII. 1867, p. 

 I 37)- Solms-Laubach, Ueber d. Fruchtentw. von Batrachospermum (Bot. Zeit. 1867). Bornet et 

 Thuret, Notes algologiques, i er fascic. 1876. Janczewski, Notes surle developpement du cystocarpe 

 des Floridees (Mem. de la soc. nationale d. sc. nat. de Cherbourg, T. XX). Thuret, Etudes phyco- 

 logiques, Paris 1878. [F. Schmitz, Unters. u. d. Befruchtung d. Florideen (Sits. d. k. Akad. d. Wiss. 

 z. Berlin, 1883); also Ann. and Magaz. Nat. Hist. 1884. Schaarschmidt, Beitr. z. Entw. d. 

 Gongrosiren, Klausenberg, 1883. Sirodot, Les Batrachospermes, Organisation, Fonctions, Developpe- 

 ment, Classification, Paris, 1884.] 



2 Once termed also spermatozoids, but this name is objectionable. 



