OF THE BRITISH FLORA. 131 



■will be as well to consider what are the characters of an insnlar 

 flora, and then see how far they agi'ee with that of Great Britain 

 and Ireland. Sir Joseph Hooker, in his lecture on " Insular 

 Floras" (reprinted in the ' Gardeners' Chronicle,' Jan. 1867), tells 

 us that the relationships between oceanic island floras are of two 

 kinds, as follows : — 



I. A relationship of analogy between themselves, due to physical 

 conditions common to all. These may be enumerated as follows ; — 



1. They are rich in ferns, mosses, and other flowerless plants. 



2. They have many evergreens. 



3. They have few herbaceous plants. 



4. They have very few or no indigenous annuals. 



5. Species which are herbs on the Continent become shrubby on. 



the islands. 



6. The species are few in proportion to genera, and genera few 



in proportion to orders. 



7. The total number of species is small when compared with 



that of a continental area of equal size and of similar 

 conditions. 



8. The mountains, however lofty, have few alpine or subalpine 



species. 



II. A relationship of hond fide kinship which the floras of 

 oceanic islands display; (1) iu common with one another; (2) with 

 certain continents or parts of them. 



The above conditions apply to oceanic islands, mostly being 

 tropical and subtropical, and can, therefore, hardly be expected to 

 be equally applicable to our own, which have undoubtedly formed 

 part of the Continent at a recent geological period. Consequently 

 the above peculiarities will be found to have but a limited appli- 

 cation. "^'^ It is not until we apply the sixth peculiarity that we see 

 any very strong resemblance, namely, in the proportion of genera 

 to species. Thus, testing it by the Ranunculacete, this order has 

 30 genera and 550 species, while the British Isles have 14 

 genera and only 40 species ; so that, avoiding fractions, we may 

 say that while our flora has 50 per cent, of the genera, it 

 has less than 8 per cent, of the species. Similarly with regard 

 to the order Umbelliferfe, which contains 150 genera and 1300 

 species, the British Isles possess 38 genera and 65 species ; that is 

 to say, about 25 per cent, of the genera, and only 5 per cent, of 

 the species. f With regard to the relationship of aflinity, there are 



* With regard to the third peculiarity, it may be noted that we possess 94 

 shrubs and trees (considering Ruhus, Eosa, and Salix as inchiding twenty-nine 

 species in all), and recognising our flora at about 1600 species, the proportion 

 will be nearly 6 per cent. Taking trees alone as about fitty of the above, they 

 give for themselves a proportion of about 3 per cent, of the whole flora, 

 in New Zealand, flowering trees alone form one-sixth of the flora, or more than 

 16 per cent. 



t As an illustration of Xo. 6. In Xew Zealand "the number of natural 

 orders is large in proportion to genera ; being as 92 to 282, or about I to 3 ; 

 while the genera are to species as 282 to 730, each genus having on the average 

 only 2^ species ; whence it follows that there are, on the average, but 8 species 



