. An introduction to the study of seaweeds. Algae. CHLOROPHYCE^ 169 motionless spores within large sporangia. These spores, which are round and provided with a membrane, do not germinate in the ordinary way but become them- selves small plantlets with a rhizoid attachment. These either soon give rise to a filamentous thallus, or, becoming enlarged, are transformed into new sporangia, the actual outcome of which has not yet been observed. In Urospora and Ehizoclonium there is a method of vegetative propagation by the separation of vegetative cells densely packed with con- tents. In Urospora the

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. An introduction to the study of seaweeds. Algae. CHLOROPHYCE^ 169 motionless spores within large sporangia. These spores, which are round and provided with a membrane, do not germinate in the ordinary way but become them- selves small plantlets with a rhizoid attachment. These either soon give rise to a filamentous thallus, or, becoming enlarged, are transformed into new sporangia, the actual outcome of which has not yet been observed. In Urospora and Ehizoclonium there is a method of vegetative propagation by the separation of vegetative cells densely packed with con- tents. In Urospora the filament breaks up first into multicellular parts- and eventually into single cells. These either germinate directly or, after surrounding themselves with thick walls and resting, produce zoospores. In Ehizoclonium the process is sim- ply that of the cells becoming rounded and dropping off; they germinate by the production of a filament in all cases. The Gcograpliical Distribution. —Glaclojjhora has a world-wide distribution in both salt and fresh water. Cluxtomorpha is also extensively distributed, but mostly in the sea. Rhizoclonium has a similar distribution to Cladophora. All three genera are represented by numerous species, many of them. Fig. 52. — Gltcetomorjpha Darwini (reduced).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.. Murray, George Robert Milne, 1858-1911. London, New York, Macmillan