30 
James Small. 
Exception has been taken to the teleological suggestion 
contained in the expression “ economy of corolla material leads to 
the aggregation of the flowers into a capitulum ” (29, p. 459) and 
the actual economy of corolla material effected in the capitulum 
has also been questioned. In the close crowding of the florets 
from the earliest stages it is obvious that aggregation has reached 
in the capitulum a stage where the food supply and space available 
for development of the young florets, exerts a distinct effect upon 
the size of the corolla. My opinion is that aggregation with its 
advantages in increased conspicuousness, etc., produced reduction 
in the size of the individual florets by the overcrowding which took 
place. This reduction would give further opportunity for the 
exercise of the tendeny to aggregation already present in the plant. 
Thus there would be a continuous reduction andaggregation mutually 
interacting until the limit of efficiency was reached. That limit is 
apparently reached in the disc and ray arrangement of the 
capitulum. The Dipsaceae, Valerianaceae and the Umbelliflorae 
are examples of the imperfect development of these two tendencies. 
In the compound capitulum of Echinops, the dense corymbs, 
panicles or glomerules of capitula in many of the Eupatorieae, 
Vernonieae and a few genera in other tribes there is evidence of the 
continuance of this action and re-action beyond the limit of full 
efficiency. 
Reduction in size would give marked economy of material 
and this, being useful, would tend to preserve the species showing 
the maximum reduction compatible with full efficiency. In the 
past, therefore, aggregation has led to economy, but at the 
present time it is economy which is the cause of the continued 
existence of the aggregation. 1 
In considering the actual economy of corolla material effected 
one must remember that before the aggregation into a capitulum 
took place, the ancestral Composite flower had developed into a 
tubular, few-seeded, high type flower, (cp. 34), visited chiefly by the 
higher insects, so that a comparison of the number of mature 
plants resulting from the seeds set in a capitulum must be made 
between the Composite and such cohorts as the Tubiflorae and the 
Umbelliflorae, where the flowers are few-seeded and aggregated 
only to a certain extent. Compare, for example, the capitulum of 
1 That the tendency to further aggregation is still present, but held in 
check, is shown by the various forms in which the capitula are grouped in the 
larger inflorescences and by anomalies such as the development of several 
concentric rows of secondary capitula in the bracts of the primary capitulum 
in Inula glandulosa, (25). 
