234 THALLOPHYTES. 



other Algae by the absence of spermatozoids endowed with independent motion, and by 

 the very remarkable female apparatus for fertilisation, which, however, in its simpler 

 forms, shows considerable resemblance to that of the Coleochsetae. 



The Thallus of the Florideae consists, in the simplest forms, of branched rows of cells, 

 which elongate by apical growth and transverse division of their apical cell, while the 

 branching of the other cells not unfrequently developes sympodially. An apparent 

 formation of tissue occurs in many Ceramiaceae (G. Cramer, Physiolog. u. system. 

 Untersuch. iiber die Ceramiaceen, Zurich 1863) from the branches growing closely 

 adpressed to their mother-axes, and thus surrounding them with a cortex, reminding one 

 of the formation of the cortex in Chara. In other Florideae the thallome is a flat expan- 

 sion of cells, but often consisting of several layers ; in some (as Hypoglossum and Deles- 

 seria) it assumes the contour of stalked leaves, even the venation being represented ; in 

 others {e.g. Sphserococcus and Gelidium) it consists of filiform or narrow strap-shaped 

 masses of tissue, which ramify copiously, so that the whole thallome often presents 

 the most beautiful forms (e.g. Plocamium, &c.). In all these cases Nageli asserts 

 (Neuere Algensysteme, p. 248) that apical growth takes place from an apical cell (in Peis- 

 sonelia possibly from several). In the simpler forms the segments of the apical cell are 

 formed in one row by transverse divisions, in others in two or three rows by oblique 

 walls. One group which comprises a large number of species, the Melobesiacese 

 (Rosanoff, Mem. de la Soc. Imp. des Sci. Nat. de Cherbourg, vol. XII. 1856) forms disc- 

 like thallomes, which grow centrifugally at the circumference and are closely attached 

 to the substance on which they grow, which generally consists of larger Algae ; they 

 resemble Coleochcete scutata in their size and mode of life, but their thallome generally 

 consists of several layers, and the cell-wall is encrusted with lime. 



The asexual organs of reproduction take the form of Tetraspores, which replace, in a 

 certain sense, the swarm-spores of other Algae, but are not endowed with motion, and 

 remind one in some respects of the gemmae of the Hepaticae. When the thallome con- 

 sists of rows of cells, the tetraspores are produced in the apical cell of lateral branches ; 

 in the rest (with the exception of the Phyllophoraceae, according to Nageli) they lie im- 

 bedded in the tissue of the thallome, often in branches of peculiar shape and densely con- 

 gregated in great numbers. The tetraspores result from the division of a mother-cell, 

 and are often arranged in it in the corners of a tetrahedron, but also frequently in a row, 

 or like the quadrants of a sphere. Sometimes the four spores are replaced by only one or 

 two, rarely by more than four (Nageli) ; in the Nemalieae they are altogether wanting. 



The sexual organs, Antheridia and Trichogynes, are produced on other plants of the 

 same species, thus pointing to an alternation of generations, and the sexual plants are 

 frequently dioecious. 



The Antheridia are either single cells at the end of the branches which consist of the 



fluorescence if left behind when the red colouring matter (the phycoerythrine) has escaped from 

 them from injury to the cells ; the whole plant also remains green when the red colouring matter 

 has been extracted by water or destroyed by heat. (Rosanoff in Compt. Rend. April 9, t866j. 

 Besides the chlorophyll-grains coloured red by phycoei7thrine, Cohn found in Bornetia colourless 

 crystalloids of an albuminous substance which are coloured a beautiful red by the colouring matter 

 that escapes from the chlorophyll-grains when the cells, are injured or killed. (Schultze's Arch, fiir 

 mikr. Anat. III. p. 24.) Cramer had pre\dously observed crystalloids of this kind in Bornetia which 

 had been preserved in a solution of sodium chloride, and had accurately described them ; according 

 to him they are partly hexagonal, partly octahedral. (Vierteljahrschr. der naturf. Ges. in Zurich, VII.) 

 Julius Klein (Flora, no. 11, 1871) found colourless crystalloids in Griffithsia barbata and neapolitana, 

 Gongoceras pelhicidjmi, and Callithamnion semitmdnni ; and states that the red crystalloids which are 

 also found outside the cell-cavity only appear after treatment with sodium chloride, alcohol, or 

 glycerine, since their colourless matrix takes up the diffusible red colouring matter of the Florideaa. 

 On Phycoerythrine see Askenasy, Bot. Zeitg. no. 30, 1867. [Sorby, "Monthly Mic. Journ. vol. VI. 

 1 87 1, p. 124. Van Tieghem has detected starch in the Floriderc, Compt. Rend. 1865. — Ed.] 



