ALGA'S CONTINUED: CLASSIFICATION. 



t75 



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

 or more auxiliar}- cells before the sporocarp is finally formed. Examples 

 are Rhabdonia, Polysiphonia, 

 Callithamnion, Dudresnaya, 

 etc. (fig. 1 89). The auxiliary 

 cell then develops the sporo- 

 carp. See fig. I So for conju- 

 gation of a filament from the 

 fertilized procarp mth an aux- 

 iliary cell. 



380. Uees 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 Hch- 

 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, mdely distributed in the 

 northern Atlantic is known as 



let 



Fig. iSo. 

 Dudresnaya purpurifera. /r, trichogyne, with 

 sperm cells attached, ct, connecting-tube 

 whicTi grows out from below the base of the 

 trichogyne, and conies in contact with the fertile 

 branches f , f ; ct\ young connecting-tube. (After 

 Thuret and Bomet.) 



"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 foUomng orders are recognized in the red algae: 



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

 atropurpureaj in springs and brooks in Xorth America and Europe. Por- 

 phyra contains a number of species forming broad, thin, leaf-Hke 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 Ehodomeniales. — In this order occurs Gracilaria and Poly- 

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



385. Order Cryptonemiales. — Examples are Dudresnaya, Melobesia, 

 CoralUna, etc., the last two genera include many species with a mde dis- 

 tribution. 



