sporophyte individual is pretty well advanced — in most species until the 

 leaves, roots, and stem are definitely formed. And it is through the materials 

 and activities of the grandparent that the seed is protected and finally sent off 

 into the world on its own. 



Parenthood in Seed Plants^ Seed plants have come to be tremendously 

 effective organisms as absorbers of material and of sun energy. Each individual 

 expends a considerable part of this accumulated material and energy in ways 

 that do not help it at all. The making of fiowers and seeds, for example, do not 

 contribute to the well-being or safety of the plant. 



And advance in the scale of life seems to impose additional burdens upon 

 the organisms. But these are more than compensated by the additional ad- 

 vantages. In a species that produces well-stored seeds, well-protected seeds, 

 and seeds well adapted to wide dispersal every individual gets the full benefit of 

 this additional expenditure of energy at the very beginning of its career. We might 

 even say that a plant is able to do its life's work effectively just in proportion 

 as it gets a good start. In doing things for posterity a plant is thus merely 

 returning to the species what it received from its immediate ancestors. 



Of course we are not to suppose that the plants do this or that because they 

 have any feeling of gratitude, or ability to foresee future needs. In speaking 

 of the advantages or disadvantages of various types of behavior on the part of 

 plants, we merely note that certain kinds of doings may actually contribute 

 to the prosperity of the species, whereas other kinds of doings might lead to 

 the extinction of the species. Some plants behaved in a certain way in past 

 ages, and their progeny today occupy the surface of the earth. Other plants 

 behaved quite otherwise, and we know of them only by the traces they have 

 left in the ancient rocks of the hills. 



In Brief 



The essential organs in all flowers, pistils, and stamens are those that have 

 to do with producing seeds. 



The pistil, or female organ, consists of a stigma, a style, and an ovary, 

 which bears the ovules. 



The stamens produce pollen, spores that give rise to male gametophytes, 

 within the anthers. 



Within the ovule a single large cell, the embryo sac, gives rise to the female 

 gametophyte, the egg-producing organ. 



The egg nucleus, generated within the embryo sac, and the sperm nuclei, 

 generated within the pollen grains, each have but half the number of chro- 

 mosomes found in the parent tissue cells. 



^See No. 7, p. 415. 

 413 



