182 
THE PLANT WORLD. 
plant parts. A progressive tendency toward fusion and a retro¬ 
gressive tendency toward multiplication. The first may be illus¬ 
trated by the cohesion of the anthers iii certain cucurbitaceous 
forms and by the union of petals in many corollas. The second 
appears normally in double flowers. It appears teratologically 
in so-called “ twin ” flower spikes where on one enlarged pedicel 
two buds are produced, or where several flowers are crowded 
together in one plane in a position where there would normally 
be but a single individual. These instances involve an enlarge¬ 
ment of parts due to the union of one or more members. Under 
this head comes fasciation as defined above. 
Worsdell concludes that of the structures mentioned each rep¬ 
resents the final product of two tendencies, one which makes for 
integrity, and which is the younger, and another which makes 
for plurality or separation. In its older parts the structure ex¬ 
hibits the tendency to fusion but later in the younger region the 
tendency to branch. In the development of fasciation there is 
the same phenomenon as that presented in the staminal group 
of a flower-like Hypericum, or one of the mallows. The union 
below and the multiplication above results from the same conflict 
of forces though the two instances are morphologically so widely 
separate. 
The mechanical cause is probably a disturbance and multipli¬ 
cation of “ growth centers.” The growth at the apex of a normal 
shoot is distributed around a central point, the growth center, in 
such a way that its transverse component is a circle and the cir¬ 
cular section of most plant axes is the result. A multiplication 
of growth centers due to obscure physiological conditions pro¬ 
duces distortions. When some centers are weaker than others, 
the curvatures result. Dichotomy is due to the influence of two 
equal growth centers and may be called the simplest form of fas¬ 
ciation. An organ tends to revert to its ancestral conditions 
when its equilibrium is upset, and' Worsdell is inclined to think 
that the banding of a fasciated stem is a reversion to branching 
in one plane like Lycopods, Ferns and Algae. 
Physiologically fasciation is probably a pathological state 
usually induced by superabundant nutrition. It has long been 
