berry

How to Know the Fruits

Here is a key to the main categories of Angiosperm fruits. The importance of fruits cannot be underestimated. They are the dispersal mechanisms for the seeds of flowering plants.

Whether the seeds are dispersed by wind, water, animal intervention, mechanical propulsion, or whatever; the fact remains that plants can't "walk", they need to get their seeds out there away from the parent population. That flowering plants dominate the terrestrial environment just shows how successful fruits have been.

Key is after Porter, C.L., 1967: Taxonomy of Flowering Plants. W.C.Freeman and Co.

Following the key is a breakdown of some fruit dispersal methods (after Scagel, et al, 1966: An Evolutionary Survey of the Plant Kingdom. Wadsworth Pub.Co.)

 ===========================================================================
Key to Types of Fruits

1. Fruit derived from several flowers............MULTIPLE FRUIT
                                              (pineapple,mulberry,fig)
1. Fruit derived from a single flower

 2. Derived from more than one pistil............AGGREGATE FRUIT
                                               (strawberry,raspberry)

 2. Derived from a single pistil.................SIMPLE FRUITS (see below)

  3. Fleshy fruits, usually indehiscent (not splitting open)

   4. Flesh of fruit derived from the floral tube or
        hypanthium surrounding the papery carpels......POME 
                                                   (apple,pear,quince)

   4. Flesh of fruit derived from the ovary wall.

    5. Fruit with outer fleshy layer and inner bony
         layer which forms the "pit" or "stone"........DRUPE (peach,cherry,
                                                     avocado,coconut,olive)

    5. Fruit fleshy throughout.........................BERRY (tomato,grape)
       
         Berry modifications are defined as follows:

     6. Divisions (septa) evident in cross-section; outer
            layer of fruit leathery (the "rind").......HESPERIDIUM 
                                                     (citrus family)
     6. Septa not evident; outer layer leathery to
             hard and woody............................PEPO (gourds,
                                                     cucumbers,melons)
                                                       
  3. Dry fruits, dehiscent or indehiscent
     
   7. Fruit indehiscent (not splitting open)
      
    8. With one or more wings..........................SAMARA (maple,ash)

    8. Without wings

     9. From compound pistil, becoming hard and bony-shelled
                                                .......NUT or NUTLET
                                                   (acorns,mints,borages)

     9. From simple pistil, maybe thin shell but not bony

      10. Ovary wall fused to the seed.................GRAIN (CARYOPSIS)
                                                       (grass family)

      10. Ovary wall free from seed....................AKENE 
                                                     (composite, buckwheat
                                                       families, et al.)
   7. Fruit dehiscent (splitting open)

    11. From a simple pistil (one carpel)
 
      12. Splitting on two sutures or "seams"..........LEGUME (pea family)

      12. Splitting on one suture......................FOLLICLE
                                                   (milkweed,larkspur)

    11. From a compound pistil (2 or more united carpels)

      13. Carpels separating from each other but retaining seed
                                                 ......SCHIZOCARP
                                                    (parsley, mallow
                                                  and geranium families)

      13. Carpels splitting, releasing one or more seeds.

        14. Fruit 2-celled, the two valves splitting away from a
              persistent thin partition or septum......SILIQUE or SILICLE
                                                        (mustard family)

        14. Fruit 1-several-celled, partition not persistent if fruit
              2-celled.................................CAPSULE (a very
                                                    common fruit! See below)                                                     fruit! see below)

          Variations on the Capsule theme:
            
          15a. Opening by a lid (circumscissile)

            16. With a single seed.....................UTRICLE (pigweed)

            16. With several seeds.....................PYXIS (Portulaca)

            
          15b. Opening by holes near top...............PORICIDAL CAPSULE
                                                          (poppy)

            
          15c. Opening by splitting lengthwise

            17. Splitting on the septae................SEPTICIDAL CAPSULE
                                                          (Yucca)

            17. Splitting between septae and in the locules or
                   chambers............................LOCULICIDAL CAPSULE
                                                         (lily, Iris)
 ============================================================================

Some ways in which fruits disperse their seeds:

Water
Rainwash, such as flooding, or raindrops splashing seeds out of an open "splash cup" (e.g. Mitella, Sagina). Aquatic plants are adapted to float fruits downstream. Coconuts float on the ocean to the next shore.
Animals
Dispersal is internal (the animal eats the fruit) or external (the animal gets the fruit caught in its fur, feet, feathers,etc.) Edible fleshy fruits are designed to be eaten. The seeds will usually survive the digestion process, and even benefit from it. Next time you pull the "burs" out of your socks, consider that you are dispersing some flowering plant as Nature designed it. "Sticky" mechanisms range from glue-like secretions that fasten the fruits/seeds to an animal (Mistletoe) to vicious-looking hooks and barbs (ever seen a Unicorn Plant?)
Wind
Wind dispersal ranges from light-weight fruits and seeds, to winged and plumed fruits and seeds, to tumbleweeds. The "plumed akenes" of Clematis and Cercocarpus are local examples. And, of course, the Dandelion Tribe....
Mechanical dispersal
Many fruits simply "explode" when ripe, hurling their seeds for some distance. Lupines and other legumes do this. The Geranium Family uses a "sling" mechanism on its schizocarps. And a bizarre example is the "squirting cucumber", a fleshy fruit that adjusts turgor pressure inside the gourd so that at a certain point, the end pops open and the seeds squirt out.

Return to Milo Baker home page

Page created May-June, 1997 -Nancy Harrison