136 Bibliographical Notices. 



whether this he owing to the former existence of some intermediate 

 land {i. e., to the north-west of Europe having once formed a portion 

 of the same floral region as North America), or whether the plant 

 was conveyed across the Atlantic hy some means of ocean transport 

 at a remote period, no more than one species is quoted in proof of 

 this link of connexion, — Spiranthes gemmipara being proved pecu- 

 liar to Ireland and distinct from the American S. cernua, while Ana- 

 charis Alsinastrum and SisyrincMum anceps are recent importations. 

 Potentilla tridentata, as a British plant, rests upon very dubious 

 authority ; and the identity of the Scotch Alopecurus alpinus with the 

 American or European species is not sufficiently ascertained. Here, 

 too, we much need a more exact knowledge of the comparative 

 abundance, in their different localities, of the arctic species common 

 to both continents. Not the least objection to the idea of marine 

 transport having been sufficient to establish the Eriocaulon in its 

 present Scotch and Irish stations consists in the difficulty of ex- 

 plaining its position in so many mountain lakes, whose waters flow 

 towards the sea, instead of being able to convey the seeds from the 

 coast inland ; the fact too of its being found in many different locaUties 

 unconnected with each other, is another point in favour of its being 

 aboriginal. 



Great Britain claims more than a seventh of the whole number of 

 European plants — about one-third of those found in Middle Europe 

 (France, Germany, and Switzerland). In the present diversity of 

 opinion as to the value of species, Mr. Watson adopts 1400 as the 

 figure best adapted for general comparisons ; other writers reckon 

 as many as 1 800, while a free use of the combining system will reduce 

 our flora to about 1000. 



"With respect to the numerical value of the orders, Filices, Jun- 

 cacece and Orchidacece hold a higher position in the British series than 

 in the European, — the prevalence of the two former being no doubt due 

 to the humidity of our insular climate, as is the high position of 

 Leguminiferce in Middle Europe indicative of its drier and warmer 

 clime (p. 412). The resemblance is closer between Britain and 

 Scandinavia, than between either of these and " Middle Europe." 

 Mr. "Watson states that he would prefer to measure these differences 

 *' by ascertaining which of the important orders present the widest 

 dissimilarities" (p. 406). 



The "vegetation" of a country is quite different from its " flora," — 

 the flora being simply the list of species, the vegetation the mass of 

 individual plants. The terms "rare," "frequent," "common" are 

 in use as a rough method of indicating the comparative abundance of 

 individual plants ; but it is clear that a more precise estimate is to 

 be derived from the "Census of species" contained in the sixth 

 chapter of the ' Cybele ' (already quoted), where the^ plants are 

 arranged in the order of their comparative frequency. 



In the Ordinal census of the vegetation of Britain, Composites still 

 take the lead, next come Gramina, then Cyperoides, following in the 

 same order as they do when arranged by the number of their species : 

 but here, from their greater abundance, Leguminiferce take precedence 



