58 BOTANY. 



prolongations, in the form of lateral branches. Reproductive organs consist 

 of spores, which are contained in mother-cells or perispores, or sporocarps. 

 These are sometimes congregated together in receptacles of different sorts. 

 The spores occasionally divide into three or four cells, constituting tctraspores. 

 In addition to spores or sporocarps, there are sometimes round, or clavatc, 

 or filamentous cellular bodies present, to which some give the name of anthe- 

 ridia. In some of the simplest Algte, the whole plant is concerned in 

 producing new individuals by dinsion of the parent cells into two or 

 four. In others there is a union of two filaments, and a passage of certain 

 granular particles (cndochrome) 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 CoiifervacecB and 

 DiatoniacecB. 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 ; hence called zoospores. In the higher Algfe, the 

 sporocarps containing two, four, or more reproductive cellules, are united 

 together in conceptacles along with filaments containing phytozoa, and 

 called antheridia. In CJiaracece. there are two distinct organs of re- 

 production. 



Sub-order 1. DiatomacecB : inhabiting still waters and moist places ; 

 fronds consisting of frustula or fragments, which are either angular or 

 cylindi-ical, often silicious and brittle (non-silicious in Desmidie^e) united 

 by a gelatinous sort of substance ; propagated by the division of parent 

 cells into tAvo halves, which become more or less completely detached, and 

 form new individuals. Conjugation also takes place in some instances, in the 

 same way as in the Confervaceae. 



Sub-order 2. Confervacem : aquatic plants often of a green color, con- 

 sisting 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. PI. 54, fig. 34, a-d; a, 

 Conferva bombycina ; b, C. rivularis in various states : c, C. flaccida and d, C. 

 glomerata. 



Sub-order 3. FloridecB, or Ceramiacem : rose or purple-colored sea-weeds, 

 with fronds formed of a single row of articulated cells, or of several rows of 

 cells combined into a flat expansion ; organs of reproduction consist of sporo- 

 carps or perispores, intermixed with clavate filaments called antheridia. The 

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

 inclosed in conceptacles of various kinds. 



Sub-order 4. Fucacecs, or sea-weeds, the sea-wrack tribe : usually growing 

 in salt water : frond consisting of cells which are often united by gelatinous 

 matter, and which sometimes form a broad expansion (a membranous 

 thallus), supported on a stalk ; organs of reproduction consist of sporocarps 

 and antheridia, contained in conceptacles opening externally, which are 

 58 



