MENDEL1SM 3 



clue has shown the way into a realm of nature which, for 

 surprising novelty and adventure, is hardly to be excelled. 

 It has led us into a new world the very existence of 

 which was unsuspected before." I shall first show you 

 how Mendel gradually developed his theories, and then 

 proceed to describe some of the later results achieved by 

 his followers. 



Let us first consider Mendel's Method. 



His practice was to select two plants, such as two peas, 

 which differ in some well-marked character — such as height 

 of stem, colour of flowers, or shape and colour of the seeds, 

 and he produced offspring from these contrasted plants, 

 using one as the male and the other as the female parent. 



In order that this may be clearly understood it is neces- 

 sary to know how plants are normally reproduced ; and in 

 case there may be some one present who does not under- 

 stand this, it will be well briefly to describe the process. 

 Almost any plant will answer the purpose, but we will take 

 a primrose shown in section in Fig. i. Within the tube 

 of the flower (the corolla), and attached to it, are some 

 small bodies called anthers, which 

 contain a fine powder called pollen. 

 When the anther is ripe it bursts, and 

 the pollen becomes dispersed. In the 

 very centre of the flower is the pistil, 

 surmounted at the top by a little 

 knob called the stigma, which is 

 generally covered with a sticky juice. Fig. i. 



The lowest part of the pistil is called the ovary — a hollow 

 chamber containing small bodies called ovules. These 

 ovules eventually develop into ripe seeds, as a result of 

 uniting with the pollen contained in the anthers. 



How does the pollen from the anthers reach the ovules 

 in the closed ovary ? When the anther bursts, and the 



