Introductory. 17 



means other than by seeds, as by non-sexual spores (52), 

 bulbs (352), stolons (348), cuttings (358), etc., and it 

 is a common method of reproduction in certain of the 

 lower animals, as plant lice (aphidse)., 



18. Heredity and Variation. The offspring of a plant 

 or animal tends to be like the parent or parents. 

 But no two beings can be begotten and developed in 

 exactly the same environment, and since environment 

 always affects the individual more or less, it follows 

 that no two individuals can be precisely alike. Varia- 

 tion in the offspring may take place in any direction, 

 as in the size or color of the flower, the sweetness or 

 juiciness of the fruit, the prolificacy, the. vigor (9), or 

 the hardiness (10), etc. It follows that in culture cer- 

 tain individual plants or animals are more desirable to 

 the cultivator thain others, because the individuals 

 possess different qualities. 



19. The Principle of Selectioii. Since the offspring 

 tends to resemble the parent or parents, we may gradu- 

 ally improve plants or animals in the direction of 

 greater usefulness by sele'cting the most desirable indi- 

 viduals for reproduction. F^or example, by saving and 

 planting seeds from the plants that produce the finest 

 petunia or pansy blossoms, we secure finer flowers than 

 if we gather plants without regard to parentage. 



20. Breeding in plants and animals is reproduction, 

 watched over and directed by man, with reference to 

 securing special qualities in the offspring. It is based 

 on the principle that the peculiarities of the parent or 

 parents tend to be reproduced, and may be intensified, 

 in the descendants. But before we are prepared for 



