Floral Evolution. 
381 
the passage through Contorts to Tubiflorae is relatively clear. We 
have surmised that the line now under consideration led to a 
hypothetical Apocynal Stock, in which the tendencies to an isomerous 
androeciumanda hicarpellary ovary, already foreshadowed separately 
in Geraniales and Sapindales, are combined, being realized in the 
Contort/e. Of these we have separated Oleaceae and Salvadoraceae 
as representing a line determined by excessive working of the 
Economy Tendency in both mega- and micro-sporangia, naming 
the group Jasminales. 
A third line emerging from the vicinity of the Apocynal Stock 
led, we suppose, to the reduced and specialized Plantaginales. 
This line is determined by the adoption of a particular and definite 
habit and by the aggregation of the small flowers into dense 
pedunculate spikes and heads. There seems to be no convincing 
evidence for the view that the Plantains are descended from any 
of the higher Tubiflorae. 
The Apocynal Plexus gave rise directly to the Tubiflor/E with 
isomerous androecium and regular flowers, our so-called Transitional 
Group, the Polemoniales of Bentham and Hooker. The connection 
is seen especially clear in Convolvulaceae ; and the flowers of many 
of the higher Tubiflorae of various families recall their apocynal 
parents. 
The fundamental distinction between the Transitional Group 
and the higher Tubiflorae lies in the zygomorphy of the corolla and 
consequent oligomery of the androecium in the flowers of the latter. 
The close connection between the two groups is seen in comparing 
Solanaceae of the former group with Scrophulariaceae of the latter. 
The tendency to zygomorphy and staminal oligomery is pronounced 
in Solanaceae, and the Transitional Group is recalled in the sub¬ 
regular isostemonous flowers of Verbascum. 
The zygomorphy of the higher Tubiflorae is held to be directly 
dependent upon insect-visits and so induced in the individual flower. 
It is thus independent of aggregation of florets into dense inflorescences 
which induces zygomorphy in the outer members. Two distinct 
“types” of zygomorphy are thus discernible, which we may name 
respectively the Individual Type and the Aggregate Tyye. Both 
types are illustrated in special and restricted circles of affinity 
throughout the Dicotyledons; but it is in the passage from the 
Transitional to the Higher Tubiflorae alone that Individual Zygo¬ 
morphy has operated as the critical tendency of descent in the 
evolution of a large and varied existing group. Aggregate Zygomorphy, 
