266 Mr Mackay's Flora Hibernica. 



known species introduced for the first time into our Flora, besides a 

 new genus called Syncesia, constructed to receive a rather obscure 

 plant allied to Arthonia.* Dr Taylor has performed his share in the 

 Flora Hibernica admirably ; and we are only disposed to complain 

 of his having adhered too rigidly to the genera of Acharius after they 

 have been, by universal consent, more or less modified. 



The last division of the work, devoted exclusively to the Algce, 

 has been contributed by Mr Harvey, whose intimate acquaintance 

 with the order is sufficiently shown in Hooker's British Flora. It 

 is a department as full of interest, as the objects themselves are of- 

 ten graceful and beautiful. Mr Harvey has done his part well and 

 carefully. The Algce Britannicce of Dr Greville has to a considerable 

 extent served him as a guide, and he has adopted verbatim, with due 

 acknowledgement, that author's description of the Diatomacece, as 

 contributed to the British Flora. But Mr Harvey is no copier, — 

 he plainly investigates and thinks for himself; and his portion of the 

 Flora. Hibernica contains much valuable information. All the Irish 

 Algae he has arranged into three grand divisions, which, from the 

 colour of the seeds, he denominates Melanosperme^e, Rhodosper- 

 mem, and CHLOROSPERMEiE. In the first division we find the tribe 

 Ectocarpece placed between Dictyotete and Chordariece ; and in the 

 second division, Gloiocladece, the first tribe, containing the genera 

 Mesogloia, Gloiosiphonia and Chcetospora, precedes the Gastrocar- 

 pece. Such an arrangement exhibits new and ingenious views re- 

 specting the affinities of Eclospermece and Gloiocladece. 



In order to add some degree of interest to this article, we have 

 drawn up a table, which exhibits at one view the relative Floras of 

 England, Scotland, and Ireland, in regard to the total number of ge- 

 nera and species in each natural order ; as well as a list of those 

 British genera in which the Irish Flora is deficient. 



* Ord. Lichenes. Genus Syncesia — Thallus crustaceous. Apothecia ob- 

 longo-elongate, stellato-radiata, aggregated and immersed in scattered thallodal 

 verruca. Perithecium none. Lamina prolifera pellucid, supported on opaque 

 vertical layers. 



