GROUP V. AXGIOSPERMJ5. 



471 



grains protrude the pollen-tubes which penetrate through the tissue 

 of the style into the cavity of the ovary, and through the micropyle 

 of each ovule to its nucellus (Fig. 285 P ri). The time required by 

 the pollen-tube for this process depends partly on the distance 

 of the pollen-grain from the ovule and partly on the specific 

 peculiarities of the plant ; thus the pollen-tube of the Crocus takes 

 only from one to three days to traverse the style, which is from 

 five to ten centimetres in length ; but in the Orchids, where the 

 length of the style varies from two to three millimetres, several 

 days, weeks, or even months are needed, and it is during this 

 process that the ovules are formed in the ovary. 



The Results of Fertili- 

 sation. The Seed is de- 

 scribed on p. 414. 



The Fruit. In view of 

 the variety in the struc- 

 ture and morphology of 

 the fruit of Angiosperms, 

 a somewhat detailed ac- 

 count of it is necessary. 



The word fruit, in its 

 strictest sense, means the 

 whole product of the de- 

 velopment of the gynae- 

 ceum as a result of fertili- 

 sation (p. 61). If other 

 parts of the flower take part 

 in the formation of the 

 organ which is formed in 



consequence of fertilisation, and which contains the seed (of what, in 

 short, is commonly called the fruit), it is termed a spurious fruit 

 or pseudocarp. The apple, for instance, is such a spurious fruit, 

 for the outer fleshy part belongs to that part of the axis of the 

 perigynous flower which surrounds the ovaries and which still 

 bears the sepals (Fig. '2 A}. What are called the pips of the 

 apple are the seeds. This kind of spurious fruit is termed a 

 pome. The strawberry also is a spurious fruit : in it the recep- 

 tacle, which belongs of course to the axis, developes largely and 

 becomes fleshy and bears the true fruits (achenes) in the form 

 of small hard grains. The fig is another example of a spurious 

 fruit ; it "is, in fact, a fleshy receptacle (i.e. an axis) which bears 



FIG. 235. Diagram of an ovule shortly after 

 fertilisation ; a outer, and t inner integuments ; j 

 f unicle : k nucellns. S Embryo-sac in which is 

 the embryo developed from the fertilised oosphere. 

 The sac also contains the endosperm-cells which ura 

 ?>eing formed by free cell-formation. P The pollen- 

 tut*, passing through the micropyle, n. 



