ALG^E CONTINUED: CLASSIFICATION. 



175 



manea, etc., but fuses directly, or by a short cell or long filament with one 

 or more auxiliary cells before the sporocarp is finally formed. Examples 

 are Rhabdonia, Polysiphonia, 

 Callithamnion, Dudresnaya, 

 etc. (fig. 189). The auxiliary 

 cell then develops the sporo- 

 carp. See fig. 189 for conju- 

 gation of a filament from the 

 fertilized procarp with an aux- 

 iliary cell. 



380. Uses of the red algae. 

 Many species produce a great 

 amount of gelatinous sub- 

 stance in their tissues, and 

 several of these are used for 

 food, for the manufacture of 

 gelatines and agar-agar. Some 

 of these are Gracilaria lich- 

 enoides and wrightii, the for- 

 mer species occurring along 

 the coast of India and China. 



The plant is easily converted Fig. 189. 



into gelatinous substance Dudresnaya purpurifera. tr, trichogyne, with 



sperm cells attached; ct, connecting-tube 



(agar-agar). Chondrus cris- which grows out from below the base of the 



-j i j- -i_ j i trichogyne, and comes in contact with the fertile 



pus, widely distnbuted in the branches f, f: ct', young connecting-tube. (After 



northern Atlantic is known as Thuret and Bornet -) 



"Irish" moss and is used for food and for certain medicinal purposes. 

 Gigartina mamillosa in the Atlantic and Arctic oceans is similarly em- 

 ployed. The following orders are recognized in the red algse: 



381. Order Bangiales. Example, Bangia atropurpurea (= Conferva 

 atropurpurea) in springs and brooks in North America and Europe. Por- 

 phyra contains a number of species forming broad, thin, leaf-like purple 

 sheets in the sea. 



382. Order Nemalionales. Including Lemanea, Batrachospermum, 

 Nemalion, described above, and many others. 



383. Order Gigartinales. In this order occurs the common Iceland 

 moss (Chondrus crispus) in the sea, and Rhabdonia and Gigartina men- 

 tioned above. 



384. Order Rhodomeniales. In this order occurs Gracilaria and Poly- 

 siphonia mentioned above, also the beautiful marine forms like Ceramium. 



385. Order Cryptonemiales. Examples are Dudresnaya, Melobesia, 

 Corallina, etc., the last two genera include many species with a wide dis- 

 tribution. 



