38 INTRODUCTION. 
heterophyllus and pantothrix (now named trichophyllus and Drouetii). 
But these two last have been again subdivided into other species, 
real or supposed ; thus, they also in turn become aggregates, when 
viewed relatively to the segregates into which they have latterly 
been further separated. In using the words ‘Super-species’’ and 
‘ Sub-species,’ we are checked at the first division ; for how are we 
to designate the two halves or the three thirds of a sub-species ? 
The two words ‘ aggregate’ and ‘segregate’ can be applied inde- 
finitely to any series of combinations in the one direction, or of 
severances in the contrary direction. 
Treated in this form, the vexed question of species becomes a 
comparatively novel subject in botanical books, the right under- 
standing of which is truly a matter of much importance for young 
botanists. Hence, even at the risk of tediousness, some further 
illustration by examples may still be presented to readers. In the 
‘Handbook of the British Flora’ Mr. Bentham united two Lin- 
nean species, by sinking Ranunculus hederaceus as a ver-species, 
and uniting it with Ranunculus aquatilis ; an union sufficiently 
justifiable in the eyes of those who also combine R. tripartitus and 
R. Lenormandi with either. By that union, it will be seen, the 
two aggregate or super-species (now more usually so deemed) were 
xeduced to segregates or sub-species; and our illustration shall 
commence with this great combination of subordinate forms, 
divided and subdivided into successive segregates by other 
botanists, as here shown :— 
A. Ranunculus aquaticus (Bentham). 
1. hederaceus (Linn.) 
a. hederaceus. 
b. Lenormandi. 
2. aquatilis (Linn.) 
a. heterophyllus. 
heterophyllus. 
floribundus. 
peltatus, ete. 
b. pantothrix. 
trichophyllus. 
Drouetii, etc. 
c. fluitans. 
d. circinatus. 
