OOb ALG.E. 



new individuals by division of the parent cells into 2 or 4. In others 

 there is a union of 2 filaments, and a passage of certain granular par- 

 ticles (endochrome) from the one to the other, ending in the formation 

 of the spore. This process is termed conjugation, and is one of great 

 interest. It has been observed in some of the Confervacece and Diato- 

 macece. In certain cases, the terminal cell of the filament is that in 

 which a spore is formed without any conjugation, and in these cases 

 the spore is frequently provided with ciliary processes, which exhibit 

 for a time spontaneous movements (figs. 431-434); hence called 

 zoospores. In the higher Algae, the sporocarps containing 2, 4, or more 

 reproductive cellules, are united together in conceptacles along with 

 filaments containing phytozoa, and called antheridia (figs. 790, 791). 

 In Characece there are two distinct organs of reproduction. 



1128. This extensive order has been divided into the following sub- 

 orders : 



1. Characese: water plants formed of parallel tubes, which are sometimes en- 



crusted with carbonate of lime ; reproductive organs are of two kinds 

 a, a round red globule consisting of eight valves which enclose cells of 

 different kinds, containing granular matter and peculiar spiral filaments or 

 phytozoa (fig. 369); b, an oval nucule formed by a large central cell or 

 spore, with five elongated cells wound spirally round it, surmounted by five 

 teeth. Some consider the globule as an antheridium, and as equivalent to 

 an anther. The nucule contains the germinating body. The rotation of 

 granules takes place in the plants of the tribe (If 275, 276). 



2. Fucaceae, the Sea-wrack tribe: usually growing in salt water ; frond consist" 



ing of cells which are often united by gelatinous matter (fig. 29), and which 

 sometimes form a broad expansion (a membranous thallus), supported on a 

 stalk; organs of reproduction consist of sporocarps and antheridia, con- 

 tained in conceptacles opening externally (fig. 790), which are united in 

 club-shaped expansions or receptacles, situated at the end or margins of the 

 fronds (figs. 788, 789). In germinating, the nucleus bursts the epispore or 

 outer covering of the spore, and sends out filamentous processes. 



3. Floridese or Ceramiacese : rose or purple-coloured sea- weeds, with fronds 



formed of a single row of articulated cells, or of several rows of cells com- 

 bined into a flat expansion ; organs of reproduction consist of sporocarps or 

 perispores, intermingled with clavate filaments called antheridia. The 

 sporocarps contain cells or spores often divided into four (tetraspores), and 

 enclosed in conceptacles of various kinds. 



4. Confervacese : aquatic plants often of a green colour, consisting of one or 



more cells of a rounded or cylindrical form, united together so as to form 

 an articulated or flat frond. They increase by the merismatic division of 

 cells. Reproduction effected by spores which are formed in the interior of 

 the cells by a change in the arrangement of the granular matter, or by the 

 union of filaments of different plants, a process of conjugation, by which 

 granular matter passes from one to the other. The spores are discharged 

 by the opening of the cells, and they often have moving cilia (figs. 431- 

 434). 



5. Diatomaceae : inhabiting still waters and moist places ; fronds consisting of 



frustula or fragments, which are either angular or cylindrical, often siliceous 

 and brittle (non-siliceous in Desmidieae), united by a gelatinous sort of 



