PROF. T. H. HUXLEY ON THE GENTIANS. 113 
In foraging for information about the Gentians, immediately 
after my return to England, I took up Müller's ‘Alpenblumen’; 
and I was exceedingly struck by the views put forward in the re- 
markable page and a quarter which he devotes to a “ Rückblick 
auf die Gentianarten " (p. 348), and which I here translate :— 
“The genus Gentiana is fitter than almost any other to fur- 
nish a biological explanation, from the arrangements in regard to 
fertilization, of the systematic grouping based on morphological 
indications; and to dispose the subdivisions of the system as 
branches of a parent stem. It is primarily divisible into two 
main branches, of which the one secretes honey from the lowest 
part of the ovary, the other from the lowest part of the corolla. 
If, then, two kinds of nectarial structure have arisen from an 
original uniform nectarial structure, the common ancestor of 
these two groups must have secreted honey, both from the base 
of the ovary and from that of the corolla, as is the case, e. g., in 
Saxifraga oppositifolia ; and thus, in the one group the one half, 
and in the other the other half, must have been specially developed, 
to the exclusion of its fellow. . But itis also conceivable that the 
ancestors of Gentiana were honeyless, and that the two forms of 
nectary have been developed independently. 
* Of the one of the two main branches, we have a lateral twig 
remaining in G. lutea, which stands low down in point of deve- 
lopment, and is certainly nearest the common stem. Like 
G. lutea, without doubt, the ancestors of the genus had fully 
open flowers, with almost free petals, and tempted the appetite 
of their fertilizers, either with perfectly accessible honey, in the 
angle between the ovary and the corolla, or only with pollen. In 
any case, they were open to the visits of very various insects, which 
therefore subserved cross-fertilization irregularly and, as it were, 
accidentally (as in G. lutea), so that the occurrence of such fer- 
tilization was by no means assured, and spontaneous self-fertili- 
zation in case of need could not be dispensed with. 
“After the development of the nectaries, Bees, and especially 
Humble-bees, proved the most effective cross-fertilizers; and 
campanulate flowers adapted to them became developed. In the 
one branch, unbidden guests were excluded by the formation of 
deep passages (Saftlöcher) ; and, by the coalescence of the anthers 
into a ring round the style, cross-fertilization by Humble-bees 
was assured (Celanthe*). In the other branch, fimbris of the 
e 
* Ptychanthe (mihi). 
