ALGM OK HYDEOPHYPTA. 653 



the parent cells into 2 or 4. In others there is a union of 2 fila- 

 ments, and a passage of certain granular particles (endqchrome) 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 Gonfervacece and Diatomacece. 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 fre- 

 quently provided with ciliary processes, which exhibit for a time 

 spontaneous movements (figs. 467-470, p. 265) ; hence called zoo- 

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

 reproductive cellules, are united together in conceptaoles along with 

 antheridia containing phytozoa or spermatozoids (figs. 901, 902), and 

 archegonia, containing cells to be fertilised. The antheridia and 

 archegonia are either on the same or on different plants. 



In place of a single natural order, Algse should be looked upon as 

 an alliance of several orders. They have been divided as follows : — 



1. Melanosporeae (fii\S,s, tlack), or PhseosporeEe ((paids, dusky), or Fncacese 



(00/cos, a seaweed) : plants of an oli¥e-green or olive-brown colour, and cellu- 

 lar or iilameutous structure ; growing in the sea (sea-wrack) ; cells often 

 united by gelatinous matter (fig. 29, p. 8), and often forming a broad ex- 

 pansion (thallus) supported on a stalk ; reproductive organs consisting of 

 sporocarps and antheridia (fig. 484, p. 273), contained in conceptacles opening 

 externally (fig. 483, p. 273 ; 901), which are united on club-shaped expan- 

 sions or receptacles situated at the end, on margins of the fronds (figs. 899, 

 900). In germinating, the nucleus bursts the epispore or outer covering of 

 the spore, and sends out filamentous processes. Spores dark coloured. 



2. Ehodosporese (pbSov, the rose), or Choristosporei {xi^purTSs, separated), or 



FloridesB (flos, a flower, from the fine colour) : rose or purple coloured sea- 

 weeds, with fronds formed of a' single row of articulated ceUs, or of several 

 rows of cells combined into a flat expansion ; reproductive organs of 2 kinds, 

 monoecious or dioecious ; sporangia in the substance of the frond or in con- 

 ceptacles ; spores red or red-brown, rounded and often in fours (tetraspores); 

 antheridia containing motionless antherozoids ; a special tube called tricho- 

 gynium (90if, hair), passing from the antheridia to the sporangia, and thus 

 effecting fertilisation (flgs. 482, 485, p. 273). 



3. Chlorosporeie (xXupis, green) : plants growing either in the sea, or in fresh 



water, or in damp situations ; filamentous or membranaceous, or shapeless ; 

 usually of a grass-green colour ; reproductive organs consisting of green 

 moving spores furnished with cilia, or of spores fertilised by antherozoids 

 (figs. 479, 480, pp. 271, 272). 



In the olive, red, and green, Algse, Sorby found at least 12 different 

 colouring matters distributed very differently, in such a manner as to 

 connect, and yet to distinguish, the diff'erent groups very character- 

 istically. (See Froc. B. Soc. Lond. 1873.) 



4. "Vaucheriese (named after Vaucher) : green Alga, with single filaments mot 



septate, producing 2 kinds of reproductive cells, and ciliated spores, not the 

 result of reproduction (fig. 478, p. 269). 



5. Saprolegniese (<raTp6!, putrid) (fig. 481, p. 273): colourless aquatic filamentous 



