ALG& CONTINUED: CLASSIFICATION. 



'75 



let 



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 

 into gelatinous substance 

 (agar-agar). Chondrus cris- 

 pus, widely distributed in the 

 northern Atlantic is known as 



"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 algae: 



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 Oigartinales. 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. 



Fig. 



Dudresnaya purpurifera. tr, trichogyne, with 

 sperm cells attached; ct, connecting-tube 

 which grows out from below the base of the 

 trichogyne, and comes in contact with the fertile 

 branches f , f: ct', young connecting-tube. (After 

 Thuret and Bornet.) 



