INTRODUCTION TO CRTPTOGAMIC BOTANY. 195 



assume a truly articular form. The tetraspores in some cases 

 are scattered over the whole frond, in others collected in son, 

 or more rarely contained in special receptacles. 



171. The genera and species are for the most part very 

 widely distributed, but abound perhaps more in the northern 

 hemisphere. Nitophyllum is, however, very rare on the 

 North American coast ; while at the Cape it appears in its 

 most magnificent array, under N. venosum. Belesseria 

 Leiorieurii, Mont., an inhabitant of tidal rivers, and having 

 the livid hue of Bostrychia, ranges from the mouth of the 

 Hudson River to Cayenne, and occurs again at New Zealand. 

 Si^hcBrococcus is confined to Europe, while numerous genera 

 are exclusively tenants of the southern hemisphere. Gracilaria 

 lichenoides, the Ceylon moss, is celebrated for its gelatinous 

 quahties, as are several allied species of the southern seas. 

 Our own Oracilaria compressa is excellent as a pickle or pre- 

 serve, and very ornamental. One of the most beautiful known 

 Algae is Grinnelia AmericoMa, which abounds on the eastern 

 coast of North America, from Cape Cod to New Jersey, and 

 differs singularly from Wormshioldia sanguinea, of which it 

 is an exact analogue, in the conceptacles being scattered over 

 the surface of the frond, and not situated in the midrib. 



12. CoEALLiNACEiE, Lamx. 



Articulated or crust-like, composed of closely compacted 

 threads, impregnated strongly with carbonate of lime so as to 

 be hard, rigid, and even stony. Spore-threads tufted, springing 

 from the base of the encysted conceptacles. Purple when 

 fresh, whitish when exposed to the air. 



172. As in the preceding order, multitudes of species occur 

 which are disguised by the immense quantity of calcareous 

 matter which they appropriate ; so is there in the florid Alg^ an 

 analogous group, which, though ty no means confined to the 

 warmer seas, abounds in them far more highly, at least as regards 

 the number of species. In essential characters they approach 

 very near to the following group, but are distinguished by their 

 almost constant production of tetrasporic, instead of polysporic, 

 moniliform threads (Fig. 48, c). In outward appearance, the 

 forms which they assume are so various, that they are recog- 



13 * 



