8o FIRST GROUP. — THALLOPHYTES. 



discs formed of one or more layers of cells ; the species of the genus Corallina have a 

 cylindrical branched thallus with a group of initial cells of similar shape and size and 

 not a single apical cell at the summit. Both the tetraspores and the sexual organs are 

 found in special urn-shaped receptacles {concept acula) formed by depression of the 

 apex of a shoot, the two being on different plants. The procarps are formed from the 

 cells which occupy the bottom of the conceptacles ; the development advances from the 

 centre to the circumference. But while the trichogynes in the centre prepare for con- 

 jugation by a club-shaped swelling at their apex and in other ways, the trichogynes at 

 the margin of the disk formed by the procarps are fewer in number and shorter. Solms 

 found no trichogynes in a receptive condition on the marginal procarps ; yet it is from 

 the marginal procarps that spores are produced. 



While in the majority of the Florideae one sporocarp (cystocarp) proceeds from each 

 procarp, in Corallina only one fructification is formed in each conceptacle, but it is never- 

 theless formed by the development of the whole of the procarps ; for after the fertilisa- 

 tion of the central procarps with perfect trichogynes all the carpogenous cells of the pro- 

 carps are fused into one by absorption of the separating walls. The carpogenous cell- 

 fusion thus formed produces spores along its whole margin, and therefore from the car- 

 pogenous cells of the marginal procarps which are fused in the general mass ; this 

 happens in C. mediterranea in such a manner that from the indented undulating mar- 

 ginal edge club-shaped cells grow out in large numbers, which are separated by a 

 wall from the carpogenous cell-fusion and produce spores by transverse divisions. 

 Thus while the central procarps have lost the power of producing spores but retain 

 their receptivity, the converse has taken place with the marginal ones ; the spores 

 proceed from their carpogenous cells, while their trichogynes are impotent. 



The division of labour goes still further in Dudresnaya'. Here certain procarps 

 have lost their receptive apparatus, the trichogyne, altogether, and their carpogenous 

 cells are fertilised by other procarps, which have the receptive apparatus, but whose 

 carpogenous cells produce no spores. The trichogyne of these procarps is the hair- 

 like pointed terminal cell of one of the cell-rows that form the thallus. When the 

 trichogyne has conjugated with the spermatia, or with one of them, long pluricellular 

 tubes grow out of the trichophores. These tubes effect the fertilisation of the carpo- 

 genous cells of the procarps which have no trichogynes ; they lay themselves on 

 them, the intervening portions of cell-wall are absorbed at the point of contact, and 

 a portion of the contents of the fertilising tube passes into the carpogenous cell from 

 which a sporocarp is then developed. A similar mode of fertilisation is found in Polyides 

 rotundiis, the Squamarieae, and others. 



V. FUNGP. 



The Fungi are chiefly distinguished from the Algae by the absence of chloro- 

 phyll in their vegetative organs, in consequence of which they are dependent for 

 their food on the organised substance of other plants or of animals. But it was 

 pointed out in the general remarks of the Thallophytes that the Fungi are here 

 considered separately from the Algae not on account of this physiological character, 

 but because, with the exception of the Myxomycetes and Schizomycetes which have 



' The essential points only in the process of fertilisation are given in the text ; the details are of 

 a more involved character. See Bornet and Thuret, loc. cit. [Also Berthol, Die Cr}'ptonemiaceen, 

 in vol. IV of the Mittheil. d. Zool. Stat, zu Neapel.] 



^ De Bary, Morphologie u. Physiologie der Pilze, Flechten, u. Myxomyceten, Leipzig, 1866. 

 [See also his Vergleichende Morphologie u. Biologie der Pilze, Mycetozoen u. Bacterien, Leipzig, 1884, 

 for a complete account of the group and its literature up to the present time.] — For special investi- 

 gations see under the separate divisions. 



