FLOWERS AND THEIR USES 281 



from a flower of a diflerent variety or species. It is plain 

 that such a thing may happen in the case of wind-pollinated 

 plants whose pollen is blown about in all directions ; it hap- 

 pens also in insect-pollinated plants, because as a rule a 

 particular insect visits several or many kinds of flowers. 

 However, a hybrid does not always result when strange 

 pollen lands upon the stigma of a flower ; for often the 

 pollen of one species will not gerrhinate upon a stigma of 

 another species ; and even if the pollen grain does germinate, 

 the pollen tube that grows from it may not reach the ovary, 

 or if it does, the unlike gametes may not be able to unite. 

 So hybrids are not so frequent as one might expect from 

 the lavish way in which flowers produce and distribute their 

 pollen. 



Generally speaking, a hybrid is more likely to be formed 

 the more nearly related the plants are to which the gametes 

 belong. Thus there are many hybrids known between 

 varieties of the same species. Many common garden 

 varieties of roses, carnations, strawberries, peas, corn, and 

 other cultivated plants are descended from hybrids of this 

 sort. There are fewer, but still a good many, hybrids known 

 between distinct species ; and occasionally one is formed 

 between plants of different genera. Hybrids may be pro- 

 duced by artificial pollination — that is, the pollen may be 

 transferred by hand from a flower of one variety to the 

 stigma of a flower of another variety. When this is done, 

 care must be taken that the same stigma is not also dusted 

 with pollen of a flower of its own kind. For this reason, the 

 flower that is artificially pollinated is kept covered from a 

 timfe when it is quite young until after it has set seed and 

 its stigma and style have withered. If it is a perfect flower, 

 its stamens must be removed before they are ripe, so that 

 none of their pollen can possibly reach the stigma. A hy- 

 brid usually combines in a new way some of the qualities of 

 one parent with some of the qualities of the other parent. 



