268 



PART III. THE CLASSIFICATION OF PLANTS. 



more complex structure the gonidangia are developed internally, 

 within the superficial layer of tissue. The gonidangia may be 

 scattered over the surface of the shoot, or collected into special 

 receptacles of various forms. In some cases (e.g. some Rhodome- 

 laceae, such as Dasya, Chondriopsis, Polysiphonia) the gonidangia 

 are confined to certain specially modified branches (gonidiophores) 

 which are termed stichidia. The tetragonidia are set free as 

 spherical unciliated cells without a cell-wall. 



The sexual organs are antheridia and procarps ; they are 

 usually borne by distinct individuals, but in some cases on the 

 same (e.g. Grateloupia, Halymenia, Hala- 

 rachnion, Nemastoma, Dudresnaya coc- 

 cinea and purpurifera, Gloeosiphonia 

 capillaris, Helminthora divaricata). 



The antheridia are small and unicel- 

 lular; in the simple filamentous forms 

 they occur singly or in groups at the 

 ends of the branches ; in others of more 

 complex structure, they are produced in 

 special receptacles (e.g. Corallinaceae) ; in 

 the flattened parenchymatous forms they 

 occur in groups on the surface ; in those 

 forms in which the shoot is differentiated 

 into stem and leaf (e.g. some Rhodome- 

 laceae such as Polysiphonia fastigiata and 

 nigrescens, Chondriopsis tenuissima) the 

 antheridia are confined to the leaves, the 

 whole or part of the leaf being specially 

 modified for this purpose. The male 

 cells (spermatia) are formed singly in the 

 antheridia, and are set free as small, 

 spherical or oval, unciliated cells desti- 

 tute of a cell-wall; they acquire a cell-wall at tn.e time of fertili- 

 sation; they contain no chromatophores, except in Bangiacese. 



The procarp presents considerable variety of form and structure. 

 It may be unicellular (e.g. Bangiaceae, Chantransia, Batracho- 

 spermum, Lemanea, Nemalion), or multicellular, as is more com- 

 monly the case. The unicellular procarp consists simply of a 

 carpogonium prolonged (except, perhaps, in Bangia) into a filament 

 termed the trichogyne. Various descriptions are given of the 

 structure of the multicellular procarp ; however, it appears to 



FIG. 193. Portion of a branch 

 of Dasya elegans, bearing a 

 stichidium (s), with tetragoni- 

 dangia (t); t' empty tetragoiii- 

 dangium. (x 25: after Kiitz- 

 ing.) 



