B8 GrevillEj on the genus Auliscus. 
pair), and that they retain their distinctive (specific) cha- 
racters/^ And he also assumes that "species vary more 
than is generally admitted to be the case/^"^ 
In adopting these assumptions, for they express my own 
convictions, we still have to acquire a practical insight into 
the laws which govern the limitation of species and the 
range of variation. So involved in obscurity are those laws, 
that one of the most cautious and philosophical naturalists in 
America does not hesitate to say — " It is by no means 
difficult to believe that varieties are incipient or possible 
species, when we see what trouble naturalists, especially 
botanists, have to distinguish between them, — one regarding 
as a true species what another regards as a variety, when the 
progress of knowledge continually increases rather than 
diminishes the number of doubtful instances ; and when 
there is less agreement than ever among naturalists as to 
what is the basis in nature upon which our idea of species 
reposes, or how the word is to be defined/^f This is strikingly 
illustrated in the most recent works devoted to the Flora of our 
own country. Scarcely two of our leading botanists take the 
same view of what constitutes (in practice) a rigid diagnosis. 
In five of the British genera of flowering plants (admittedly 
difiicult and testing examples), the following difl'erences 
occur in two Floras. According to Professor Babington 
there are 24 species of Ranwiculus, 45 of Rubus, 1 7 of Rosa, 
32 of Hieraciumj and 70 of Car ex. According to Mr. 
Bentham there are 13 species of Ranunculus, 5 of Rubus, 
5 of Rosa, 7 of Hieracium, and 47 of Carew ; being a dif- 
ference in only five genera of one hundred and eleven species. 
This extraordinary contrast might possibly be attributed to 
certain extreme views entertained by the authors of these 
Floras. This may be the case, and parties who difier from 
them both will no doubt say so ; but who is to decide ? The 
matter is infinitely complicated by other and equally dis- 
tinguished botanists holding not exactly an immediate posi- 
tion, but oscillating in a most irregular manner between the 
extremes. Sir W. J. Hooker and Professor Walker- Arnott 
describe in their British Flora 4 species of Ranunculus fewer 
than Babington, and 7 more than Bentham ; of Rubus, 34 
species fewer than Babington, and 6 more than Bentham ; of 
Rosa, 2 more than Babington, and 14 more than Bentham ; of 
Hieracium, the same number as Babington (32 — one extreme 
being here reached), and 25 more than Bentham; of Carew, 
* 'Flora of New Zealand/ "Introductory Essay," p. viii. 
f Professor Asa Gray, 'Nat. Selection not inconsistent with Nat. 
Theology/ p. 5. 
