138 Bibliographical Notices. 



from the circumstance of their Himrisliinp: equally either in freeh 

 or in salt water. The fruetilirution ul' lUtnijla ha.s hitherto been ob- 

 Bcure ; it has recently been investigated by Dr. Cohn in ' Schulze's 

 Archiv,' IbliT, Band iii. 



In the second family, the C/i<(iitra)tsi(HC(f',theTc is but one genus, 

 C/iaiitniiisia, And the thii'd family, the Bittrai-hospermacei^e, con- 

 tains only two, liatrachospermum and Thorca. The former genus 

 lias lately been the subject of some very interesting observations by 

 Messrs. liornet and Thuret* and the Comto de JSolms-Laubachf. 

 These obscrvei-s have independently arrived at similar conclusions 

 with regard to the mode of reproduction in Batnuhospermmn. The 

 details cannot be given here, and, in fact, would be hardly intelli- 

 gible without figiu-es. The observations of Messrs. Boruet and 

 Thiu"et are not confined to the genus Batrachospenmnn, but extend 

 to a multitude of other Florideif, and seem at last to have solved 

 the problem as to the mode of sexual reproduction in that tribe of 

 Algae. 



Ulhlenhrandtia is the only freshwater genus in the fourth family, 

 the Hildenbntndtiacece. It has been the subject of some observa- 

 tions by Mr. Carter in Seemann's ' Journal of Botany ' for 1864, 

 p. 225. 



Lemanea, Bory, a singular genus, beautifidly figured by Kiitzing 

 in his ' Phycologia Generalis' (pi. 19), and Compsopojon of Mon- 

 tague, represented in Europe by a single species, Compsopogon Cori- 

 naldii, Ktz. {Lemanea Corhuddii of Meneghini), compose the fifth 

 and last family, the Lemanea cece, with which the work closes. 



It is hoped that enough has been said to give a sufficient idea of the 

 nature of Dr. Rabenhorst's work, and to show the important assistance 

 it will render to all who are engaged in the study of freshwater .Algae. 

 The difficulty of making any entirely satisfactory classification of 

 plants so little resembling one another as the diff"erent tribes of 

 Algae is very great. In judging of any arrangement, it will always 

 be necessary to bear in mind that (as Messrs. Bornet and Thuret 

 have remarked) the name " Algae" does not represent " un ensem- 

 ble nettement limite,"' that it is, in realit)-, only a common name 

 under which are comprised families belonging to different types, and 

 which have often no other affinities than the absence of vascular 

 tissue and the medium in which they grow. 



With these remarks, we can cordially recommend the work before 

 us as an indispensable addition to the libraries of aU algologists. 



Microscopic Objects fujured and described. By John H. Martin, 

 Secretary to the Maidstone and Mid-Kent Natural-History Society. 

 No. I. London : John Van Voorst. 



We welcome with much satisfaction the appearance of this unpre- 

 tending but most useful collection of dra-wings illustrative of the 

 microscopic appearances presented by an extensive and well-selected 



* Ann. d. Sc. Nat. s^r. 5. vol vii. p. 144. 

 t Bot. Zeit. May 1807, nos. 21 and 22. 



