ILLINOIS NATURAL HISTORY SURVEY MANUAL 1 
Petals, and to some extent sepals, by being joined for part 
or all of their length, present a variety of forms, regular and 
irregular. Certain types of joined corollas are subu/ar, others are 
bell shaped. A narrow tube that flares into a wide-spreading 
border, called the /imd, is salverform. If the tube graduates 
into the border instead of diverging suddenly, the corolla is — 
funnelform. The junction of tube and limb is the throat. Flowers 
whose petals spread out at once, with no tube or a very short 
one, and radiate like the spokes of a wheel, are wheel shaped. 
Arrangement of the flower organs.—We have seen that the 
organs are in sets or whorls around the center of the flower, 
but we will also need to consider the relative heights at which 
they are attached. 
Fig. 5.—ATTACHMENT OF THE FLOWER PARTS. a.—Hypogyny. 
b.—Perigyny. c.—Epigyny. 
The stem or flower stalk that supports a solitary flower or a 
flower cluster is called the peduncle. The stalk of an individual 
flower within a cluster is the pedice/. The upper end of the flower 
stalk, to which the flower parts are attached, is the receptacle. 
Alteration in the shape of the receptacle produces the three 
forms of flowers shown in fig. 5. A convex or conical receptacle 
has the sets of organs placed upon it one above the other, the 
lowest being sepals, next petals, then stamens and finally pistils. 
Such a flower is hypogynous, and the ovary is superior, a. In 
other flowers the receptacle is cup shaped and the calyx and 
corolla are attached to its edge, around the pistil but entirely 
free from it. Such a flower is perigynous,b. Finally the receptacle 
may be concave, enclosing the ovary and grown fast to it. Here 
the other parts are attached to the receptacle above an inferior 
ovary, and the flower is epigynous, c. 
Flower clusters—A plant may bear only one flower or it 
may have several or many in clusters. Each cluster is an 
inflorescence, of which there may be one or many on the plant. 
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