Students sometimes experience difficulty in deciding whether a particular specimen is a fruit or a seed. It is very important to understand that from a scientific point of view, a fruit is quite different from a seed. This difference can be from its morphology, structure, mode of formation and other distinguishing physical features. A fruit is a fully-ripened gynacium and is therefore a seed-container. The two will differ clearly in there external characters. The following explanations and descriptions would help in scientifically distinguishing a fruit from a seed.
A fruit is usually stalked, the stalk being the flower pedicel, whereas the seed shows a scar, the helium, where the funicle attached it to the placenta.
The fruit nearly always carries the withered remains of one or more styles; the seed never does.
On the seed, a micropyle or pore can sometimes be seen; there is no such structure on a fruit. This difference would become more obvious if the specimen is dissected. If the fruit is many-seeded, there is usually clear distinction between the individual seeds and the pericarp of the fruit which encloses them. Each seed will have its own protective covering, the testa, within the pericarp and quite clearly separate from it.
A one-seeded fruit, such as achene or nut, especially a small one, may be more easily confused with a seed. A clear indication that the specimen will b eobtained during dissection, if not from external characters, since there will be two distinct layers to remove, the pericarp and testa, before the embryo is disclosed. The exception to this is the caryopsis, in which pericarp and testa become fused as a single layer. The occurrence of a cupule, which may entirely enclose the fruit, can until mature, can also cause indecision. Dissection of such a structure will clearly show three protective layers outside an embryo, the outermost being the cupule.
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