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Figure 8.16 Dry fruits that do not split at maturity. A. Achene of a sunflower split open. B. Grain (caryopsis) of corn, cut lengthwise. C. Nuts (acorns) of an oak. The acorn on the right was cut lengthwise above the cup.

Samara In samaras, the pericarp surrounding the seed extends out in the form of a wing or membrane, which aids in dispersal (Fig. 8.17). In maples, samaras are produced in pairs, but in ashes, elms, and the tree of heaven, they are produced singly.

Schizocarp The twin fruit called a schizocarp (Fig. 8.18) is unique to the Parsley Family (Apiaceae). Members of this family include parsley, carrots, anise, caraway, and dill. Upon drying, the twin fruits break into two one-seeded segments called mericarps.

Aggregate Fruits

An aggregate fruit is one that is derived from a single flower with several to many pistils. The individual pistils develop into tiny drupes or other fruitlets, but they mature as a clustered unit on a single receptacle (Fig. 8.19). Examples include raspberries, blackberries, and strawberries. In a strawberry, the cone-shaped receptacle becomes fleshy and red, while each pistil becomes a little achene on its surface. In other words, the strawberry, while being an aggregate fruit, is also partly composed of accessory tissue.

Samaras Fruit
Figure 8.17 Samaras of a big-leaf maple (Acer macrophyl-lum). Maple samaras are produced in pairs that separate at maturity.
Schizocarp
Figure 8.18 Schizocarps of carrots. A schizocarp separates at maturity into two one-seeded fruitlets.

Multiple Fruits

Multiple fruits are derived from several to many individual flowers in a single inflorescence. Each flower has its own receptacle, but as the flowers mature separately into fruitlets, they develop together into a single larger fruit, as in aggregate fruits. Examples of multiple fruits include mulberries, Osage oranges (Fig. 8.20), pineapples, and figs. Pineapples, like bananas, usually develop parthenocarpi-cally (see Chapter 23), and there are no seeds. The individual flowers are fused together on a fleshy axis, and the fruitlets coalesce into a single fruit.

Figs mature from a unique "outside in" inflorescence. The individual flowers of the inflorescence are enclosed by the common receptacle, which has an opening to the out

Crawling Flowering Plants Aggregate Outside Receptacles

Figure 8.1Q A. Ablackberry flower. Note the numerous green pistils. B. Blackberries, representative of aggregate fruits. (B. Courtesy Robert A. Schlising)

side at the tip (Fig. 8.21). Such a multiple fruit arrangement is referred to as a syconium. Some fig varieties develop parthenocarpically, but others are pollinated by tiny wasps that crawl in and out through the opening. Some multiple fruits, such as those of the sweet gum, are dry at maturity.

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