126 Historical Sketch of Improvements in [Aug, 



perdon solidum of the flora Virgin. Trans. Linn. Soc. xii. And 

 Klias Tries has pubUshed in the Stock. Trans, an arrangement of 

 the Scleromyci, in which he describes no less than ^10 species of 

 spheria, divided into 13 sections, and the paper is not yet con- 

 cluded. 



Als;ce. — The knowledge of the algoe is perhaps the most imper- 

 fect of any of the departments of natural history, on account of 

 the difficulty of obtaining and examining any considerable num- 

 ber of them ; besides, the fresh-water algae present so little 

 beauty to the eye, being in general only simple threads of a green 

 colour, which, on drying, lose their distinctive characters, inas- 

 much as the chloroma, or green matter contained in their tubes, 

 and probably their seed, although sufficient, when the plants are 

 fresh, to distinguish them, becomes totally insufficient for that 

 purpose when they are dry, as it is no longer distinguishable from 

 the general mass. 



Dr. Nies, as above stated, has found, like Mr. Drummond, that 

 several of the confervae and ulvte, are in fact immature plants of 

 musci, or lichenes. This is the case with conferva frigida, C. 

 castanca, and ulva rupestris. These plants are of great import- 

 ance in forming the first soil at the bottom of water, and even of 

 the sea, whose bed is gradually raised by a species of conferva, 

 the C. chthonoplastes. 



LinntEue arranged the alg£E in only four or five genera ; and. 

 this contented the botanists for a long time, till Roth, in his 

 Tentamen Florae GermanicjE, began, but with a sparing 

 hand, to augment the number. Vaucher, in his Histoire des 

 Conferves d'Eau douce, was moi-e bold ; and Lamouroux, in his 

 Essai sur les Genres de la Famille des Thalassiophytes non arti- 

 culecs, examined the fucoides and ulvaceae; arranging them 

 principally by their organization and habit; as the marine algae 

 can seldom be found in a state of fructification. 



Agardh has adopted much of the method of Lamouroux ; and 

 although he has only peculiarly examined those that grow in the 

 Northern countries, he gives a systematic arrangement of nearly 

 the whole family, with reference to the authors who have treated 

 of them at greater length. He divides the algse into four sec- 

 tions: 1. Fucoideee; 2. Floridese ; 3. Ulvoidese; 4. Confer- 

 voideae and Tremellinse ; which are afterwards subdivided into 

 45 genera. 



This family has also been very much illustrated by the labours 

 of Hans Christian Lingbye, who published this year his Ten- 

 tamen Hydrophytologise Danicse, in 4to. with 70 plates, con- 

 taining from three to six figures each. He divides them into — 

 1. Phycoidata, frondose, continued, solid, flat, compressed, or 

 round; 2. Soleniata, frondose, continued, tubular; 3. Stereo- 

 gonata, frondose, jointed, round, solid ; 4. Siphonogonata, fron- 

 dose, jointed, round, tubular; 5. Homalogonata, frondose, 

 jointed, flat; 6. Tremelloidata, gelatinous. Under these ar- 



