Origin and Development of the Composite?. 223 
local, slightly sheltered conditions in the mountains and also with 
the short “ summer ” season. Such forms rendered possible the 
invasion of the open tracts in the lower regions and the Spilanthes 
type was the result. 
The lower Eocene was now well advanced and Seuecio had 
proceeded north to the Rockies, where the greater rainfall and less 
intense insolation rendered both the stunted, shrubby habit and the 
large-leaved xerophytic habit unnecessary. The usual Seuecio of 
these regions was, therefore, of a herbaceous perennial type. The 
earliest progeny of the genus naturally accompanied the parent, 
Gnaphalium travelling along the higher mountain levels and 
Spilanthes along the foot-hills and alpine meadows. 
The mountain habitat formed by the slowly rising Rockies was 
comparatively restricted and the successful invaders from the Andes 
extended their zone of occupation to the wooded regions of the 
plains. There the setose pappus would be of little use as a means 
of wind-despersal. Accordingly, the tendency to fusion of the setae 
had more or less free play and the ten-awned type of fruit repre¬ 
sented by Carpolithus liyoseritiformis was developed, the rest of 
the plant remaining very similar to the parent Spilanthes. Animal 
denizens of the forest would be much more efficient seed-dispersers 
than the gales which scarcely penetrated below the forest roof. 
The development of the free ends of the setae into hooks, erect as 
in Coreopsis or recurved as in Bidens, was, therefore, a very suc¬ 
cessful experiment; so successful indeed that the latter of these 
experimental forms spread in time all over the surface of the earth. 
Senecio travelled far and wide along the paths mapped out by 
the isolated hills and mountains, w hich by the end of the Eocene 
had appeared in most of the now mountainous regions of the world. 
The development of the different types would naturally be greatest 
nearest the Andine centre, where the numbers of individuals would 
also be greatest. The less arid conditions of the Rockies favoured 
a large development of the herbaceous forms. The lapse of time 
had given the tendency to elaboration of the style branches an 
opportunity to develop the elongated appendages characteristic of 
the Astereae; the evolution of the fimbrillae and alveoles of the 
receptacle and the aggregation of the cauline leaves to form a 
multiseriate calyculus had also been carried forward several stages. 
The most noteworthy result of these changes was the development 
of Solidago during the middle Eocene in the central region of 
North America. By that time the four main types of Composite had 
beeninitiated,i'.e.,the Senecioneae, Inuleae, Heliantheae, and Astereae 
