Bibliographical Notices. 135 



M. Ripart (Ann. d. Sc. Nat. 5" ser, vol. ix. p. 80), with regard to 

 3Ioi((/cotia. Mougeot'm genufiexa is figured at p. 112 in the ' Con- 

 spectus Generum,' but in the description at p. 258 it is made a 

 synonym of PUurocarpvs viimbilis, Al. Br. If Phurocar/nts 

 ')n'rabilis, Al. Br., and Moiujeotia genvflexn were really identical 

 (which, however, is probably not the case), there could be no possi- 

 ble ground for the substitution of the name PJeurocarpus for that 

 of Mou;/eotia, the latter having been established by Agardh in 1824, 

 more than thirty years before the date of Braun's Pleurocarjms. 



The remaining genera of the Zygnemece call for no special remark, 

 except that it is very doubtful whether Mesocarjjus is worthy of 

 being retained, or whether it ought not to be united with Mougeot'm. 

 The Siphophycem constitute a small order, divided into two families, 

 the Hydrogasfrce and the Vaucheriacece. Each family is composed of 

 only one genus. The former is rei^resentedhj Hydrogast rum, Desv., 

 better known under the name Botrydium, which name, however, is 

 of five years' later date. The latter family is formed of the genus 

 Vaucheria, which of late years has been the subject of interesting 

 observations with regard to its method of impregnation. 



Dr. Rabenhorst's fourth order, the Nematophycece, is divided by him 

 into seven families: — 1. Ulvaeece; 2. SpjlueropJeaceo} ; 3. Confer- 

 vacece ; 4. (Edogoniacece ; 5. UlotricJiere ; 6. Chroolepidiece ; 7. Chcvto- 

 phoreo'. In the Dlvacecn we have six genera, the first four of which, 

 viz. Protoderma, Prasiola, Physodictyon, and ScJiizomeris, are very 

 obscure, nothing whatever being known of their mode of propagation, 

 not even zoospores having been observed. The other two genera 

 are the well-known Enteromorpha and Ulva. It would be bold to 

 question the validity of these long-established genera ; but, unless 

 llobiji's assertions are correct (and, although made some years since, 

 they do not appear to be confirmed), no sexual reproduction is 

 known ; and the occurrence of zoospores is a matter of little moment 

 now that it is known that those bodies are not confined to Alga% 

 but that they occur also in genera of Fungi, such as Cystopus, 

 Peronospora, and Trichia, and, under favourable circumstances, 

 even in the gonidia of lichens. 



The second family of the Nematophycece is the Sphrnropleacece, 

 represented by the single genus SphceropJea, which possesses but 

 one species, SpliaropJea annidi)ia, a plant growing in Germany in 

 fiooded fields, and extremely interesting from the observations made 

 a few years since by Cohn with iTgard to its sexual reproduction*. 



The Confervacece- (the third family), as hmited by Dr. Kabenhorst, 

 consists of but nine genera, the best-known of which is CJadophora , 

 of which nine species are described ; but the well-known variability 

 of the plant is exemplified by the number of divisions, forms, &c. 

 into which the genus is cut up. In the present work the three 



Part III.) are called " Zvgnemacefe " at p. 110. So, afterwards, "Ulo- 

 trichec-e " (p. 286) are called " Ulotrichacea} " at p. 3G0 ; and " Chteto- 

 phore.e " (p. 287) are called " Cha;topboracepe '' at p. 374. 

 * See Ann. d. Sc. Nat. 4'' ser. vol. v. p. 187. 



