Dry Fruits – a botanical classification
A fruit is a seed-bearing structure that develops from the ovary and surrounding tissue. The seeds are enclosed within the ovary wall. If the wall becomes hard, the fruit is classified as Dry. (If it becomes succulent the fruit is classified as Fleshy). There are 2 types of Dry Fruit. Those that split open (dehisce) to release seeds and those that do not. First we look at those that split open.
There are two types that form from ‘free’ carpels – Follicles and Legumes.
A Follicle is formed from a single carpel. The follicle splits down one side along the suture and contains more than one seed. Hellebore has 4 follicles, one of which is shown open. Also found in Delphinium, Sedum and Magnolia.
A Legume is a 2-valved fruit formed from a single carpel that, when ripe, splits down both sides, along the sutures. Typical of the Pea Family. Photo of Laburnum.
There are 6 types of dry dehiscent fruit that are formed from ‘fused’ carpels and so have number of compartments known as ‘locules’.
A pod-like fruit that is formed from two united carpels. It splits down both sides and the 2 valves open to reveal the seeds attached to a central partition. If it is more than 3 times as long as broad it is a Siliqua (photo of white mustard).
If the capsule is less than 3 times as long as broad it is a silicula.(Photo of Honesty). Typical of the Cabbage family.
The capsule splits longitudinally along the dorsal suture of each locule, (i.e. not at the septum) as shown in this photo of the Stinking Iris. The whole capsule splits into 3 parts called ‘valves’ to release the orange seeds.
The capsule is made up multiple non-overlapping segments. These valves open from the top as shown in this cross-section of a Dianthus capsule and the seeds fall out as the wind shakes the capsule
Pores open around the top of the capsule as seen in this photo of the Poppy. Seeds are shaken out of the pores as the poppy sways in the wind.
Splits from the top along the lines of the septum of the ovary as shown here in the Foxglove. It has an axile placenta with a septum that splits the ovary into 2 compartments. The split occurs where the septum grows out from the wall. The septum can be seen in the middle with style attached.
There are 4 types of Dry Indehiscent Fruits (dry fruits that do not split open to release seeds)
An achene is a single-seeded fruit that does not split open. This photo shows the achenes of a Clematis vitalba. The brown seed is formed when the superior ovary wall hardens and the plume is a feathery extension of the style.
Cypsela A type of Achene that includes non-carpellary tissue.
In the Dandelion shown here the brown seeds have a hairy parachute (pappus) attached to aid dispersal. The pappus is formed from the calyx and because this is not from the carpel it is called a Cypsela. Achenes of this type are also found in Scabious and Valerians
A nut is a single seeded fruit with a woody coat that does not split. Found on Oak, Beech, Sweet Chestnut and Hazel. The nut sits in a cupule which is formed from the flower bracts. In the oak and Hazel the cupule does not enclose the nut but in the Beech and Sweet Chestnut it encloses several nuts and splits open to release them.
A Samara is a dry winged fruit found in Ash,shown here, and in a double form in the Maple. The double fruit of the Maple may be called a schizocarp by botanists – it is a fruit that splits into one-seeded portions called mericarps.