224 
James Small. 
New conditions were required for further marked differentia¬ 
tion and these were attained when Senecio reached the Mediterran¬ 
ean region, by way of Alaska, Siberia and the Asiatic mountain 
ranges. The shrinkage of the Great Central Sea, which at one 
time stretched from the Gulf of Mexico to the Deccan, and the initial 
development of the Alps in upper Eocene times prepared a new 
land for Senecio to conquer. The low hills with abundance of 
marshland, and the sub-tropical climate combined to produce 
marshy woods and low-lying meadows in which the setose pappus 
was again of little use. Other experiments in fruit dispersal were, 
therefore, made here. Animal dispersal, especially by birds, was 
obtained by the reduction of the pappus to a ring or auricle, and the 
edible fruit was thus exposed to view. An occasional improvment 
was effected by the development of a mucilaginous pericarp, which 
would be very efficient in such a marshy environment. These 
changes, combined with a few slight and probably mutational 
changes in the styles and sexual arrangements within the capitulum, 
sufficed to produce the Anthemideae as represented by 
Chrysanthemum and Matricaria. 
Another method of getting rid of the superfluous pappus was 
tried with success ; the pulvini of the setae, which normally act only 
in dry air, having no opportunity of exercising their usual function, 
degenerated into regions of abscission, and the pappus became 
caducous. A preliminary attempt at raising the pappus was pro¬ 
bably due to the fruit continuing growth under the predominantly 
moist climatic conditions. The initiation of both these experiments 
is seen in Lactuca, but the two methods became distinct in the 
progeny of that genus. The very rapid growth of these Cichoriaceous 
herbs was probably responsible for the re-development of latex 
which had been suppressed from the time when Siphocampylus first 
started to climb the Andes. The profound disturbance of the 
organism under a climate so different from that oftheAndine home 
of Senecio was probably responsible for the mutation which pro¬ 
duced the ligulate florets and also for the fact that the bulk of the 
Senecioneal colony in the Mediterranean region were transformed 
partly into Anthemideae and partly into Cichoriese. The origin of 
two more large groups is thus traced to the evolution of climate, par¬ 
ticularly in the Mediterranean region during late Eocene times, 
combined with the arrival of the aggressively migrating Senecio. 
About this time also the Solidago type underwent anthocyan 
changes in the corolla, possibly as the r esult of the decrease in the 
