Why do raspberries bear their seeds externally?

Answer 1

First of all get rid of the wrong notion that seeds are ever borne OUTSIDE a fruit. Not because I say so but it is scientifically FALSE.

Let us look at the definition of SEED BEARING plants.

1) Spermatophyta - All the seed bearing plants belong here.
( Here Spermos= seeds and Phyton = plant)

2) Gymnosperms - All those from 'spermatophyta' come here only if their seeds are exposed and NOT enclosed . That means seeds are there ,but fruits are not formed to ENCLOSE them as there is NO ovary in this group.
(Gymnos== Naked and sprmos = seed as usual)

All conifers and Cycads and their relatives come here. Pines etc.

3) Angiosperms= All those spermatophyta in which the seeds are ENCLOSED in side a fruit come here.
( Angion= a container or a vessel. and spermos= seeds as usual) This is possible because in ALL these plants there is an OVARY that ENCLOSES Ovules.

After fertilization and during seed formation the OVARY turns in to a fruit and OVULES turn in to seeds.

All the flowering plants come in this category including STRAWBERRY.

Now let us look at some interesting pictures.

Just click on the link.
1)http://www.sci.muni.cz/bot_zahr/fotografie/skleniky/kapradiny/Cycas%20circinalis.jpg

In the above picture of Cycas you can see prominent seeds that are totally exposed. As there is no fruit formation.

Now in strawberry what is the FACT?
Read below-
The strawberry is an accessory fruit; that is, the fleshy part is derived not from the ovaries ; but from the peg at the bottom of the hypanthium ( Base or Stalk) that held the ovaries.

So from a technical standpoint, the seeds are the actual fruits of the plant,
And the flesh of the strawberry is modified receptacle tissue. It is greenish-white as it develops and in most species turns red when ripe.

Now for the picture

http://k43.pbase.com/v3/89/415789/2/47533435.strawa.jpg

In the photo closeup, the red and juicy and edible part is the BASE ot the Fleshy stalk and the tiny , brown and not so attractive are ACTUALLY the tiny fruitlets ; Each holding one seed INSIDE!

In Raspberries --In proper botanical language, it is not a berry at all, but instead an aggregate fruit of numerous drupelets around a central core. Each druplet fruit has a seed inside. See th link for the photo.

http://en.wikipedia.org/wiki/Image:Raspberries_%28Rubus_Idaeus%29.jpg

In Blackberry- The blackberry is also the fruit of the blackberry plant. In proper botanical language, it is not a berry at all, but instead an aggregate fruit of numerous drupelets each having a seed inside. See the photo below.

http://upload.wikimedia.org/wikipedia/commons/0/0c/Blackberry_fruits10.jpg

I hope this helps!

Answer 2

Not Raspberries, Strawberries!

DID YOU KNOW?
Strawberries are a member of the Rose family. Strawberries are unique in that they have seeds on the outside. All other berries (blueberry, raspberry) have seeds on the inside. The modern strawberry is a criss-crossed hybrid of native wild strawberries (F. virginiana) from Eastern North America, (F. ovalis) the Rocky Mountain strawberry and the South American Chilian strawberry (F. chiloensis).
What most people call seeds on the outside of the strawberry fruit are actually
the true fruits. Technically, they are achenes. In an achene, the single seed is
enclosed by the ovary wall. A sunflower fruit is also an achene.

A strawberry "fruit" is unusual because the red, fleshy part is the enlarged
receptacle. The receptacle is the enlarged tip of the flowering stem to which
the petals, sepals, stamens and carpels are attached. The strawberry is said to
have an accessory fruit because much tissue other than the ovary is part of the
"fruit". Apples and pineapples are also accessory fruits.

The strawberry is also termed an aggregate fruit because it is formed from many
separate carpels of a single flower. Other aggregate fruits are raspberry and
blackberry.

Some people mistakenly refer to strawberries as a multiple fruit. In a multiple
fruit, the carpels of several flowers merge to form the fruit. Pineapple and
figs are multiple fruits.

Scientific fruit terminology is often confused. Adding to the confusion is that
there are popular definitions for fruit, nut and berry. Most "nuts" are not
botanical nuts. The peanut fruit is a legume. The walnut fruit is a drupe.
Ginkgo nuts are seeds of a gymnosperm, and gymnosperms produce no fruits. Many
berries are not botanical berries. The strawberry fruit is an achene. The
raspberry fruit is a drupe. Juniper berries are seeds of a gymnosperm.