52 
When these “flowers” are said to double, it is by trans- 
formation of the tubular flowers of the centre into con- 
spicuous strap-shaped flowers, like those of the margin of 
the inflorescence. In that case they need not necessarily 
become sterile, for in many Composites like the Dandelion, 
all the florets are normally of the ray-floret type. Another 
curious freak met with in some of the Composite when 
they receive abundant nutrition is the development of some 
of the ray-florets into small heads of flowers on stalks of 
their own, so that the large central head is surrounded by 
a number of lesser ones. This is the condition in the 
Hen-and-Chicken Daisies, and similar modifications are 
found in other plants. 
A not uncommon abnormality in gardens is the 
development of a terminal flower of large dimensions and 
regular shaped at the top of the flowering spike of the 
Foxglove; in the Snap Dragon, too, flowers showing radial 
symmetry instead of the usual two-lipped condition may 
be formed. A plant may indeed bear nothing but 
“peloric” flowers as these are called. 
Monstrosities may also occur in the development of 
fruits. Double-fruited oranges with two whorls of carpels 
(pegs) one inside the other are occasionally found, while 
in one variety known as Buddha’s fingers, the various 
carpels are only united below and taper off above into 
finely divided pod-like segments. 
“While most of these malformations are due to little 
understood intcrnal causes, many cases of excessive devel- 
opment of plant structures are produced as the response 
to irritation. Thus, numerous kinds of galls and tumours 
may be developed by animal and vegetable parasites. 
insects and fungi, which injure the tissues and cause them 
to swell or grow more vigorously. These will be dealt 
with in later chapters. 
Plants like animals have the power of protecting them- 
selves against external injury and of healing any wounds 
that are caused thereby. The most usual method is by the 
formation of layers of cork, which will protect any exposed 
part from the atmosphere, thereby preventing the excessive 
loss of moisture through the wounded surface and also 
reducing the chances of invasion of the tissues by disease 
or decay producing organisms. This development of a 
resistant layer of cork is due to the active growth of the 
living cells of the plant in the exposed region. This active 
