104 PROF. T. H. HUXLEY ON THE GENTIANS. 
In Exadenus the nectarial surfaces are hemispherically de- 
pressed and bulge outwards, so that their positions are marked 
externally by convexities of the corolla. Dr. Grisebach (‘ Genera 
et Species Gentianearum,’ p. 322) says of each “fovea glanduli- 
fera," that it is “ extus tantum conspicua, intus per petali sub- 
stantiam clausa;" but the real state of the case appears to me to 
be as I have stated it. Exadenus, in fact, represents the first 
stage of a transition from Actinanthe to the next type. 
II. Keratanthe. 
This differs from the preceding in no essential respect, 
except in the deepening of the nectarial concavities, in such 
a manner that their external walls project as long horns or 
spurs, which are sometimes directed downwards and sometimes 
upwards. Moreover, the lobes are relatively shorter, and the 
corolla is more or less campanulate. It is very possible, and 
indeed probable, that further inquiry may bring to light forms 
constituting a complete transition between Actinanthe and 
Keratanthe. 
The genus Halenia is the only representative of this type. 
III. Lophanthe. 
Here, again, the corolla has fundamentally the same cha- 
racters as in Actinanthe; and the only essential difference lies 
in the development of filamentous appendages, or fimbri®, 
from the inner surface of its cup. These fimbrie occur in 
different positions: sometimes they are parastemonal ; that 
is to say, they arise singly or in groups from a common base, 
along, or close to, the line of symphysis of the filaments of the 
stamens with the cup of the corolla. In this case they are some- 
times so minute as to be distinguishable only by the aid of the 
microscope ; sometimes, on the other hand, they are so long as to 
extend across the interval between one series and another, and 
thus to form a more or less complete barrier across the interval 
between the ovary and the corolla. These fimbrie have already 
been noticed in some of the species in which they occur; but 
which the cup more or less closely embraces the ovary, and is even narrower at 
the summit than the middle. The physiological import of the two forms is very 
different ; and, morphologically, the latter are really hypocrateriform eorollte 
with very long lobes. I use the term “ rotate” in the first sense. 
