128 BibUograpldcal Notices. 



ley's ' Introduction to Cryptogamic Botany ' abounds with interest- 

 ing rcmai'ks upon various genera, but does not profess to systema- 

 tize lower than orders. The treatises of Mr. Rails and of the late 

 Professor Smith have deservedly acquired a classical reputation ; 

 but they are only monographs of special families. There is an 

 immense amount of accurate information scattered through the 

 pages of the ' Micrographic Dictionary,' Avhich, if coMected, ar- 

 ranged, and somewhat amplified, would go a long way towards sup- 

 plying the deficiency. Dr. Gray's useful ' Handbook ' is only in- 

 tended as a catalogue to assist in the arrangement of Algae for the 

 herbarium, and does not contain any specific characters. 



It is therefore a great satisfaction to meet with a work which has 

 gathered up the great mass of scattered information relative to the 

 Algse of Europe which inhabit fresh or brackish water ; it aff'ords 

 a sort of resting-place from which to start afresh for the investiga- 

 tion of the numberless questions which still remain to be deter- 

 mined with regard to the plants now under review. No one Avould 

 be more ready than Dr. Ilabeuhorst himself to admit that his work, 

 valuable as it is, is far from exhaustive of the subject. As regards 

 one great tribe, his Phjicochromophycecf, he himself remarks that our 

 knowledge is stiU " valde imperfecta et manca ;" and indeed it may 

 be a (piestion, as Avill be seen in the sequel, whether most of the 

 genera of this division may not prove to be wholly inadmissible. 



With these preliminary remarks, we will proceed to give some 

 account of the contents of the work before us. 



Dr. Eabenhorst (as is perhaps unavoidable in treating only of the 

 freshwater Algae) departs somewhat from the hitherto generally re- 

 ceived classification. Instead of dividing the group into Cliloro- 

 sperms, Ehodosperms, and Melanosperms, he constitutes five classes : 

 ■ — 1. Diatomophiicece (or Diatomacece) ; 2. PJii/cochromopJiycea' ; 

 3. ChJoroj:)lnilloplnjcece ; 4. IlelanojtJiycece ; and 5. Rhodoplijicece. Of 

 these, the three latter comprise such of the Algae of the three divi- 

 sions just mentioned as are not removed into the Dintomophycece and 

 Phycoch ro m ophycece. 



With regard „o the first class (the DiafomojjJiycei'' or Diatomacece*), 

 there will probably be few botanists who will object to their having 

 a separate division assigned to them. Their very remarkable struc- 

 ture, their mode of reproduction, their apparent want of immediate 

 affinity with any other of the plants known as " Algae," aff'ord 

 quit^ sufficient grounds for keeping them by themselves. They seem 

 out of place amongst the C'hlorospcrms, to which they have been 

 hitherto referred, and if removed from that di\'ision it would be 

 impossible to do otherwise than to make them a class by themselves. 



Dr. Eabenhorst divides the Diatomaceo' into fourteen families. 



To go at any length into the discussion of these would occujiy 



* The term Diatomophycecp has evidently only been adopted to pre- 

 serve a kind of uiiitbrniity of nomenclature with the other four classes ; 

 but it is au awkward expression, and will certainly not be allowed to 

 displace the well-known name " Diatomacece^ 



