PRINCIPAL GROUPS OF PLANTS. 



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cavities, called conceptacles, and these contain the reproductive 

 organs. These consist of oogonia and antheridia, which may be 



FlG. 14. Some common marine algae. A, Laminaria, showing portions of three leaf- 

 like thalli and hold-fast; B, dichotomously branching thallus of Fucus; C, Sargassum, or 

 "gulf weed," showing a thallus resembling a leafy branch, with swollen, berry-like air 

 bladders, which act as floats; D, Dasya, a delicate branching filamentous sea-weed, attached 

 to a blade of eel-grass; E, dichotomously branching thallus of Chondrus, or Irish moss; 

 F, leaf-like thallus of Grinnellia; G, densely, but delicately branched thallus of Polysiphonia. 

 A, B, C are Brown Algae and D, E, F, G are Red Algae. 



present on the same or on different plants. The egg cells and the 

 sperm cells escape into the sea-water, and after their union an 



