INFANCY AMONG SEED PLANTS 293 



Among the lowest plants and animals that produce spores or 

 encysted cells, the new individual usually has a cell wall or coat 

 that is somewhat thickened. This is a means of protection against 

 drought, mechanical injury, or perhaps against the digestive juices 

 of some animal that might ingest it. The cell also contains a tiny 

 drop of oil or some other excess of food material that will sustain life 

 until the protoplasm is able to obtain food through its own activi- 

 ties. Such cells are usually produced in large numbers and are de- 

 posited in every current of water and air. Only a very small propor- 

 tion of such reproductive cells ever starts a new life. It is very largely 

 a matter of chance which one will and which one will not mature. 

 For example, mold spores are scattered by the bursting of the spo- 

 rangium. They are found practically everywhere ; but only those 

 that fall upon food in a favorable environment will develop. 



Infancy among seed plants. In the seed-bearing plants, each 

 generation receives from the preceding one a great deal more 

 than a quantity of protoplasm. The gametes are produced in 

 proportionately small numbers, compared to the reproductive 

 elements of seedless plants. The female gametes especially are 

 very few, only one to each ovule. Then there is a great variety 

 of structures whose function is to make fertilization possible and 

 probable. For example, the display of the flower by means of 

 the showy corolla and fragrance will attract the insects that are 

 in search of nectar. In taking the nectar, the insects will be- 

 come covered with pollen which they will later, accidentally, 

 transfer to other flowers. The position and character of the 

 stigma of each flower show special adaptations to catch pollen, 

 and to aid and effect the formation of the pollen tube. All these 

 are parts of the equipment of the parent plants, which aid in the 

 process of fertilization. 



The fertilized ovum or zygote is retained within the ovule. It 

 is supplied with nourishment which the young embryo uses up 

 in developing. The growth of the embryo goes on to a certain 



