136 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



warm climates. There is no representative on our own coasts, 

 though several occur in the Mediterranean; nor do they appear 

 in New Zealand. Acetahularia occurs in New Guinea, and 

 Didyosphceria in Galega and Rawack. Polyphysa is abun- 

 dant in King George's Sound. Anadyomene occurs in the 

 Mediterranean, the Canaries, and the South Sea Islands. All 

 of these appear to me nearly related to Conferva, from which 

 I think they ought not to be separated, especially while we 

 are ignorant of their fruit. Gonfervw sometimes abound to 

 such an extent, as to be extremely injurious. After floods, for 

 instance, where the water stands several days, they sometimes 

 luxuriate so much, as on their subsidence to form a uniform 

 paper-like mass, to which the name of meteoric paper has 

 been given. Till the stratum becomes perfectly dry, which is 

 a slow process, except on the outer siu-face, the smell is often 

 very disagreeable, and the gas generated from it renders the 

 meadows extremely unwholesome. Confervce afford an enor- 

 mous supply of food to aquatic animals, and when fresh, purify 

 the air by the exhalation of oxygen. Otherwise, they do not 

 seem to answer any especial purpose in human economy. 

 Pliny speaks of the virtue of Confervas, in uniting broken 

 bones, and supposes that the name is derived from conferru- 

 viinando ; but, like most Latin etymology, this is probably 

 incorrect. The natural derivation is from conferveo, on ac- 

 count of the bubbles of air which are given off by the fila- 

 mentous mass. 



5. BaTRACHOS PERMED, Ag. 



Threads incorporated into a solid axis, surrounded by gela- 

 tine, or converted into a cellular tube ; branchlets short, fasti- 

 giate, whorled, or scattered, sometimes forming interrupted 

 knots; fruit, aggregated or solitary on the branchlets, con- 

 sisting of metamorphosed cells. 



110. A small but very beautiful group of Algce, consisting of 

 gelatinous threads, variously woven into a branched cylindrical 

 frond. The superficial branches are either scattered over the 

 whole plant, or collected into little knots, which make the plants 

 appear like necklaces. They vary from green to black, passing 

 through intermediate shades of olive or purple. Fruit is pro- 



i 



