CHAPTER III 

 PROPAGATION BY SEEDS 



PLANTS reproduce themselves (1) sexually by means either 

 of seeds or sex-spores, or (2) asexually by buds or tissues 

 capable of forming buds, or by vegetative spores. Some 

 plants depend for propagating themselves on one of these 

 methods only, while others multiply by both sexual and 

 asexual means. 



48. Sexual reproduction. Two kinds of organs are in- 

 volved in the sexual reproduction of plants; stamens and 

 pistils. The stamens produce pollen-grains which fall on or 

 are carried by insects or wind to the top (stigma) of the 

 pistil. Under favorable conditions, the pollen-grain on the 

 stigma produces a tube which grows down to the egg-chamber 

 (ovary) at the bottom of the pistil. A certain nucleus de- 

 scends the pollen-tube and unites with the egg-nucleus in the 

 ovary. The egg is then said to be fertilized. As a result of 

 this process, seed is formed. 1 



49. Structure of the seed. A seed consists of the 

 following : 



1. The embryo or rudimentary plant, which is capable 

 under proper conditions of growing into the mature individual. 



2. Cotyledons or seed-leaves (one, two, or in some cases 

 more) which may or may not be a part of the embryo. 



3. Food material stored either in the cotyledons or outside 

 of them. 



4. Protective coats or coverings. 



1 The process is explained more completely in Chapter XII on pollination 

 arid fertilization. 



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