341 



bounded by right lines, icollected into a crystalliform body, and with no other 

 difference from minerals than that the individuals have the power of again 

 separating. System, xiii. The observations above quoted are those of natu- 

 ralists of so high a reputation for accuracy, that they may safely be accepted 

 as certain ; but I do not know what to say of such as the following, by a 

 German botanist of the name of Meyen, unless that they require to be verified 

 by others, especially because those who have sought for the phenomena he 

 ihentions have not succeeded in finding them. This writer states that he has 

 Seen, very often, a spontaneous motion in Zygnema nitidum ; and its fila- 

 ments contract from the length of 10 inches lo that of 4-6' lines; that the 

 Oscillatorias move in a circle ; that the globules contained in the filaments 

 of Zygnema have a life partly vegetable, partly animal, and procreate similar 

 globules, some of which become animals endowed with motion. See Agardh's 

 Species Algarum, 2. 48., from which this account is extracted. Certain 

 supposed Confervee, called Bacillarias, are rejected from plants by M. Bory 

 de St. Vincent, and placed in the lowest grade of the animal creation. See 

 ,Dict. Class. 2. 128. 



■ Other Algse approach nearly to the structure of Lichens, lose entirely 

 their animal properties, and become broad flat expansions, or finely divided 

 vegetables, such as are seen in the ordinary state of Sea-weeds, Fuci, or 

 marine Confervas. Of the British species of these, and of their general 

 nature, an excellent account has been given by Dr. Greville in his Algce 

 Britannicce , from which the greater part of the following remarks is ex- 

 tracted. While the two first groups consist of microscopic objects inhabit- 

 ing obscure places, shady paths, or half-immersed surfaces of stones and 

 banks, the more complete Alga3 comprehend species forming subaqueous 

 forests of considerable extent in the vast ocean, emulating in their own gigan- 

 tic dimensions the boundless element that enfolds them. Chorda filum, a 

 species common in the North Sea, is frequently found of the length of 30 or 

 40 feet. In Scalpa Bay, in Orkney, according to Mr. Neifl, this species forms 

 meadows, through which a pinnace with difficulty forces its way. Lessonia 

 fuscescens is described by M. Bory de St. Vincent as 25 or 30 feet in length, with 

 a trunk often as thick as a man's thigh. But all these, and indeed every other 

 vegetable production, is exceeded in size by the prodigious fronds of Macro- 

 cystis pyrifera. " This appears to be the sea-weed reported by navigators to 

 be from 500 to 1500 feet in length : the leaves are long and narrow, and at 

 the base of each is placed a vesicle filled with air, without which it would be 

 irnpossible for the plant to support its enormous length in the water ; the 

 stem not being thicker than the finger, and the upper branches as slender as 

 common packthread." 



These remarks may be concluded by a reference to the following works, 

 in which further information relating to the animal nature of certain Confervae 

 may be found : Nees von Esenbeck Die Algen des Sussen Wassers (1814); 

 Treviranus in A )in des Sc. 10. 22. (1817); Gruithuisen in Nov. Act. Acad. 

 Leopold. Curios. 10. 437.; Carus in the same, 11. 491. (1823); Gaillon in 

 Ann. Sc. Nat. 1. 309. (1823) ; Desmazi^res in the same, 10. 42. (1825), and 

 14. 206, (-1828) ; Unger in the same, 13. 431. (1828) : all of which should be 

 carefully consulted by those who wish to form any accurate judgment upon 

 this most curious and interesting subject. 



Geography. This has been treated upon carefully by Lamouroux 

 in the Annales des Scie7ices Naturelles, vol. 7, and by Dr. Greville in the 

 Alo<^ Britannicce. Algaj are most important in the economy of nature for 

 forming the commencement of soil by their deposit and decomposition. The 

 basin of the ocean is said to be continually rising by the deposit of such 



