In the pea and marrow there are many seeds, but there are large numbers of fruits in which we find only one. For example, in plums, cherries, and peaches we have a fleshy outer fruit-case with a stony lining covering over one large seed. Such fruits do not open, for there is only one seed within, and so the fruit is scattered whole. These fruits nearly always get scattered by animals, for the flesh is very sweet and attractive to eat, and then, as a rule, they get rid of the stone (which contains the seed) at some distance from the parent.
Fig. 82. Cherry fruit cut open, showing the flesh (f), stone (s), and seed S.
Sometimes we find a number of fruits just like the cherry clustered together, only instead of each of them being large, they are all very small, so that the whole cluster of fruits may be the size of a single cherry. This is the case in the common blackberry and the raspberry, where each of the little fruitlets really corresponds to a cherry.
Then there are many fruits which belong to quite a different class, and arrange to scatter themselves by the help of the wind, such as the fruits of the dandelion, thistle, and many others, which have light “parachutes,” and therefore blow away with the least puff of wind when they are ripe and dry (see fig. 83).
Fig. 83. A, head of Dandelion fruits, with most of them scattered. B, single Dandelion fruit.
Other fruits like the sycamore have big side-wings which catch the wind as they fall, and get twirled for some distance. In these cases each of the separate parts which flies is really a fruit, only in the case of the dandelion, thistle, and many others, each of these fruits contains only one seed, and the fruit itself is so small and dry that we get into the way of speaking of the whole fruit as a “seed.” This is not correct, however, because even though there is only one seed present, yet it is surrounded by the dry remains of the ripe carpel, and is therefore a fruit.