228 APPLIED BIOLOGY 



GENERAL NOTES ON SEED-PLANTS 



219. Adaptations of Seed-plants. The preceding lessons 

 on seeds, roots, stems, flowers, and fruits of seed-plantshave 

 shown some of the most important ways in which these organs 

 have become adaptively modified so as to enable certain 

 plants to carry on their life-activities (especially breathing, 

 feeding, and reproducing) better than an unmodified plant 

 could under the same conditions. Write a brief essay on 

 " Adaptations of Seed-plants," showing how at least five 

 adaptations have given plants which possess them special 

 advantage. 



Origin of the Adaptations. Just how adaptations of the 

 various organs of seed-plants have originated is unknown to 

 biologists ; but the fact that modified roots, stems, flowers, etc., 

 are built on the plan of unmodified ones suggests that origi- 

 nally they were all alike. For example, it seems probable 

 that the first flowers were very simple, and that their de- 

 scendants have developed various modifications which adapt 

 them to such important processes as pollination and seed- 

 distribution. However, it does not seem probable that 

 adaptations have been developed because they were needed ; 

 but rather that modified structures have appeared for some 

 cause or reason unknown to us, and have happened to be of 

 special use or value. For example, it seems probable that 

 certain leaves first developed in pitcher-form, not because the 

 plants required such leaves and set about to make them; but 

 having appeared as the result of causes still unknown, the 

 pitchers proved useful as insect-catchers and have been pre- 

 served, and probably improved. 



This idea that many structures developed and then later 

 found a special use and became adaptations is supported by 

 the observation that many other modified structures have 

 apparently found no use. For example, it is not known that 

 the sharp spines on a chestnut-bur are useful defenses, for when 



