CHAPTER XVIII 



FRUITS AND SEEDS 



Among the higher plants, multiplication by seed is almost 

 miiversal. The various modes of vegetative reproduction 

 supplement it, but only in a very few cases do they alto- 

 gether displace it. For this reason the higher plants are 

 called Spermaphytes, or Seed-plants, in contrast to the 

 lower plants, or Cryptogams, which multiply by spores, 

 and not by seed. 



The Fruit. — Seed-plants are divided into two groups, 

 according to whether the seeds are enclosed in fruits or 

 not. The Angiosperms, or higher flowering plants, bear 

 seeds enclosed in fruits. This fruit is usually developed 

 from the ovary. All parts of the flower are looked upon 

 as modified leaves, and the leaf-structures which form the 

 ovary are known as carpels. If the carpels are separate, 

 the ovary is said to be apocarpous (G-r. apo, from, distinct ; 

 carpos, fruit) ; if they are united, syncarpous (Gr. syn, 

 together). The number of carpels forming the ovary 

 may be one or many, and according to their mode of 

 union one or more seed-chambers are formed. The 

 ovary is, therefore, a closed structure containing one or 

 more chambers, in which one or more seeds are developed. 

 When the ovules are fertilized and become seeds, accom- 

 panying changes take place in the carpels, and these 

 become the enclosing walls of the fruit, and constitute 

 the pericarp (Gr. peri, round). In the lower group of 

 Seed-plants, the G3nnnosperms, the seeds are not enclosed 

 in carpels, but are exposed on shoots or seed-bearing 

 leaves — e.g., conifers. Nevertheless, even in Gymno- 

 sperms seed-protection is not unprovided for. In the 

 pine, for example, during the development of the seeds, 



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