6 HANDBOOK OF SEA-WEEDS. 



double system of reproduction, a distinctly sexual one, by spores 

 and antheridia, and another by tetraspores, which by some are 

 considered to be of the nature of gemmce, or buds. The spores 

 are generally situated in distinct hollow conceptacles (favellae, 

 ceramidium, coccidium). The tetraspore is also sometimes con- 

 tained m a conceptacle. It consists of a more or less globular, 

 transparent cell, which when mature contains within it four 

 (rarely three) sporules. Reproduction in the olive sea-weeds is 

 also double, by zoospores, generally considered gemmae, and by 

 spores and antherozoids, which is a sexual process. 



Following the classification adopted by Professor Harvey, 

 which is that generally employed in English systematic manuals, 

 we divide the order into three sub-orders, named from the pre- 



Fig. 2. A, Species of Gleocapsa, one of the Palmelleae, in various stages. 

 A becomes B, C, D, and E by repeated division. Magnified 300 diameters. 



vailing colour of their spores. I. Chlorospermeae, with green 

 spores; 2. Rhodospermese, with red spores; and 3. Melano- 

 spermese, with olive-coloured spores. The entire plant in the 

 first group is usually grass-green, but occasionally olive, purple, 

 blue, and sometimes almost black ; in the second it is some shade 

 or other of red, very seldom green ; and in the third, while 

 generally olive green, it is occasionally brown olive or yellow. 



The Chlorospermeze are extremely varied in form, often 

 threadlike, and are propagated either by the simple division of 

 the contents of their cells (endochrome), by the transformation 

 of particular joints, or by the change of the contents of the cells 

 into zoospores, which are cells moving freely in water by means 

 of hairlike appendages. In their lower forms they are among 



