HYBRIDIZATION. 



59 



and Cyclamen, &c, and compare with them the 

 garden forms existent to-day. In habit, size, 

 form, and colour there are vast improvements 

 from the horticulturist's point of view. The 

 same is true of our finest fruits and vegetables, 

 such as Apples, Pears, and Plums, Cherries, 

 Peaches, and Grapes, or Cucumbers and Toma- 



toes. In a word, man has adopted Nature's own 

 tactics in the garden. Like the fly or the bee, 

 he carries pollen from flower to flower, but with 

 deliberate intent, and so he can in many cases 

 readily vary or alter his crops, and render them 

 more amenable to the particular ends he has in 

 view. 



Fig. 73. —Magnified Pollen-grains. 



a, Hibiscus tematus. b, Malva rotundifolia 

 c, Campanula persicifolia; X200. 



Fig. 72. —Bees and Flowers. 



a, Part of an inflorescence of Salvia glutinosa ; the right-hand flower is being visited by a humble-bee, and the pollen-covered anther is in the 

 act of striking the insect's back, b, Spartium scoparium; in the lowest flower the keel is still closed and stretched out horizontally; in 

 the flower next above, the keel is depressed and the stamens have sprung up; the third flower is being visited by a Carpenter Bee (Xylocopa 

 violacea), and is ejecting its pollen on to the under surface of the insect's body. (Kerner.) 



The three great factors in plant improvement 

 are good cultivation, judicious cross-fertilization, 

 and rigid or careful selection. 



When it comes to actual practice, all that 

 man can do is to place the pollen from the 

 anthers of the male parent selected upon the 

 stigmas of the plant selected to bear the seeds. 

 The hybridist applies the pollen and nature 

 does the rest. The hybridist w T ill probably 

 have to deal with three types of flowers, viz. 

 (1) hermaphrodital, (2) monoecious, and (3), 

 dioecious. The first type consists of all those 

 flowers which have stamens and pistil included 

 in the same flower, as in Roses and Lilies. The 

 monoecious, or unisexual flowers, have male and 



female flowers separate from each other on the 

 same plant, and are represented by Begonias, 

 Cucumbers and Melons, Ricinus, &c. Dioecious 

 plants are those having male and female flowers 

 on distinct and separate plants, such as Aucuba, 

 Cannabis (Hemp), Spinach, and Humulus or 

 the Hop-plant. 



In the case of hermaphrodital flowers, how- 

 ever, we in many cases find some provision 

 made in order to prevent autogamy or self- 

 fertilization. In some cases the flower is 

 protandrous, i.e. the anthers ripen and shed 

 their pollen long before the stigmas of the 

 same flower are fit for fertilization. In other 

 cases the flowers are protogynous, i.e. the stigmas 



