230 
James Small. 
suppression of the ray florets and the discoid Eupatoriutn was 
produced. A very similar development occurred in the Liabnm 
group of the same region and Vernonin, which is very similar to 
Eupatoriutn in general form, was evolved. Both these genera 
spread across the Pacific archipelago during the succeeding 
periods. 
The tendency to economise in fruit production was more or less 
general in these favourable regions at the foot of the Andes and it 
became very marked in some of the Brazilian Asters. Some of the 
capitula became completely sterile. Thus Baccharis originated, 
and by travelling up and along the Andes reached such a diversity 
of habitats that it gave rise to a very varied group of species. 
In the Mexican region a considerable differentiation occurred, 
which was probably connected with the geological activity during 
the middle Miocene in and around what is now the Caribbean Sea. 
By changes in the colour of the ray florets in the Golden-rod tribe, 
similar to those which produced the Asters, Combined with the 
always recurring suppression of the pappus, the Bellidinae 
originated. 
The tendency to reduction in the number of fruits produced 
by each capitulum, which had become well developed in the 
Melampodium plexus, was carried still further: the capitulum was 
reduced to a few flowers; at the same time the large anterior lip of 
the ray florets became reduced and Clibadium (Milleriinae) was 
developed. The same two tendencies were carried to extremes 
along another line in the same plexus. Partlieninni, losing the 
aristae of the pappus and reducing the corolla of the female ray 
florets, became Parthenice. A still further reduction of the rays 
resulted in the genus Iva, in which the tendency to unisexuality of the 
flowers became so strong that unisexual capitula were developed 
in some of the other Ambrosiinae. These series, the Milleriinae and 
Ambrosiinae, represent the working out to the last possible stage 
of orthogenetic lines commenced under the influence of the success 
of the capitulum as a seed-producing arrangement, together with 
the reduction in available food material resulting from the gradual 
drying up of the originally mesophytic environment as the shrink¬ 
ing of the Central Sea continued. In the mesophytic wooded 
localities which were left the Spilanthes group continued to thrive, 
and in some rather unsuccessful forms the awned pappus of the ray 
florets was.lost by the mutation, common throughout the family, 
which resulted in the suppression of the achenial hairs and pappus. 
