78 



KNOWLEDGE. 



[April 1, 1895. 



plum are examples of this form of fruit. Compound drupes, 

 such as the blackberry and raspberry, are formed by an 

 aggregation of such drupes placed on an enlarged receptacle. 

 Each fruit is here called a drupel, and has exactly the 

 same struct ui-e as the cherry or plum. 



Such fruits as these are true fruits. In cases where 

 other parts of the flower are included, the fruits are called 

 spurious fruits. Take, for example, the strawberry. In 

 this the red swollen mass which we eat is simply the end 

 of the stalk (or " receptacle," as it is called), which has 

 become succulent, while the fruits themselves are the 

 small yeUow bodies commonly known as seeds. Again, 

 the receptacle, instead of bulging out as iu the strawberry, 

 may become hollowed out so as to enclose a cavity in 

 which are placed the separate fruits. Buch a fruit is 

 found in the fig. The fig may thus be considered as an 

 iuvaginated strawberry. 



The type of fruit termed a berry is a succulent fruit in 

 which the seeds are imbedded in a pulpy mass, as the 

 gooseberry and grape. The blackberry, raspberry and 

 strawberry, we have seen, are not true berries at all. 



The apple is a still more modified form, since the 

 calys-tube, in addition to the pericarp, encloses the seeds. 

 Here it is the calyx-tube which has become succulent and 

 forms most of the edible part of the fruit. The mesocarp 

 is also succulent, while the epicarp and endocarp form two 

 horny cases enclosing the seeds. 



Finally, let us consider the mulberry, which is the most 

 modified of all. While externally it somewhat resembles 

 the blackberry, it is iu reality entirely different, being 

 formed by a dense mass of flowers, the petals of which 

 have become succulent. 



These few familiar examples will suffice to show what 

 diverse parts of a flower contribute to the formation of 

 what are popularly known as fruits, and also how different 

 parts may become succulent. In fhe cherry, raspberry, 



blackberry, and others, it is the 

 true seed-case which becomes 

 succulent ; in the strawberry 

 and fig it is the swollen stalk ; 

 in the apple it is the calyx-tube ; 

 and in the mulberry it is the 

 petals of the flowers themselves. 

 Now let us consider the 

 reasons why some fruits are 

 succulent and others hard ; 

 why some are sweet and others 

 bitter ; why some are brightly 

 coloured and others dull. We 

 must first bear in mind that the primary object of all 

 fruits is the perpetuation of their species by means of 

 dispersing their seeds. It is obviously of advantage for 

 the seeds to be scattered over as wide an area as possible, 

 because only a certain number of plants can grow in a 

 certain area of ground. Now the seeds have no inherent 

 power of locomotion, hence they must avail themselves of 

 such opportunities as occur. The simplest agent in the 

 dispersal of seeds is the wind, and seeds which avail 

 themselves of this means are either minute, so as to be 

 easily blown about, or else they are downy — as the 

 dandelion — so that they can float a long way in the air. 

 The second means of dispersal is by animals, chiefly birds, 

 and such seeds avail themselves of this means which 

 cannot be dispersed by the wind. Animals may cause 

 dispersal of seeds in two ways ; first, by carrying earth, 

 containing imbedded seeds, in their claws. A good ex- 

 ample of this is given by Darwin ( " Origin of Species," page 

 328), who obtained a piece of earth which had been found 

 attached to the leg of a partridge, and since then had been 



en 



Fig. 2. — Diagram of Clierrv 

 (or Drupe) : ep, epicarp ; en, 

 endocarp ; m, mesocarp ; s, 

 seed. 



-ct 



Fig. 3. — Diagi'am of Straw, 

 berry, slicking enlarged recep- 

 tacle, r, covered with Aclienes, 

 or iiidiridual fruits, a. 



kept three years. From the seeds imbedded in this piece 

 of earth no less than eighty-two plants were obtained. 

 This also shows the length of time that seeds retain their 

 power of germination. The second and principal method 

 of dispersal by animals is by the seeds being swallowed as 

 food. The seeds of such fruits as are eaten by animals are 

 protected by a hard coat, which is capable of resisting the 

 action of the digestive fluids of the stomach and intestines. 

 These seeds pass out uninjured in the fieces, and are 

 dispersed by the wanderings of the animal which swallows 

 them. Fruits which attain dispersal in this way become 

 as sweet and succulent as possible, and also acquire bright 

 colours in order to attract birds and other animals. This 

 does not take place till they are ripe, for otherwise they 

 would be eaten before the seeds were mature. Take, for 

 example, the wild strawberry. The young strawberry is 

 green and sour, to prevent being eaten till the seeds are 

 mature. During the time when the seeds are attaining 

 maturity the receptacle becomes 

 red and succulent, thereby at- 

 tracting the notice of birds. 

 The birds swallow the pulpy 

 receptacle, and with it the 

 small yellow fruits, which pass 

 through the alimentary canal 

 of the bird uninjured, and so 

 become dispersed during the 

 flight of the bird. Hence we 

 see that the reason for fruits 

 becoming succulent is in order 

 that they may form attractive 

 food for birds and other 

 animals, and so ensure dis- 

 persal of their seeds. Such fruits are called attractive 

 fruits. But although this explanation will account for the 

 origin and structure of very many fruits, it clearly will 

 not do so for all. For the group of fruits comprised under 

 the term " nuts " a diflerent explanation is required. 



In the " nuts " it is the seed itself which is nutritious, 

 owing to the large store of albuminous matter destined for 

 the yoimg embryo plant. Owing to this large store of 

 food, these fruits do not require dispersal, and hence do 

 not become attractive ; on the contrary, they are repulsive 

 to animals and birds, while all their energies are devoted 

 to prevent their getting eaten in order to preserve their 

 nutritious seeds, as it is evident that these seeds, being 

 digestible, would cause destruction of the species if they 

 became eaten. Such fruits are known as deterrent fruits. 

 These deterrent fruits may be protected by a prickly coat 

 as in the chestnut, or a nauseous covering as in the 

 walnut ; and it is interesting to note that it is the same 

 part of the fruit which is filled with bitter essence in the 

 walnut that in the cherry or plum is succulent. Again, 

 deterrent fruits, instead of being brightly coloured, are 

 invariably green while on the tree and brown like the soil 

 when they fall to the ground, these protective colourings 

 increasing the security against being eaten by animals. 

 The extent of the protection depends on the animal to 

 whose attacks the nuts are exposed. The European walnut, 

 for instance, has only a few woodland animals to guard 

 against, while the American butternut has to withstand 

 the teeth of the forest- rodents. 



Take, for example, the cocoanut. This contains a large 

 store of food-stuft' intended for the embryo plant, enclosed 

 in a hard shell surrounded by a fibrous coat. The cocoanut 

 grows at a considerable height from the ground, and so has 

 to fall some distance when ripe ; the function of the 

 fibrous coating is, therefore, to break the fall of the nut, 

 while the hard shell protects it against the attacks of 



