Production of Double Flowers 511 



send me such a curious flower. One half of it 

 was completely double, while the other half was 

 entirely single, bearing normal and fertile sta- 

 mens in the ordinary number. 



The same halfway doubling is recorded to 

 occur among composites sometimes, and from 

 the same source I possess in my collection a 

 head of Pyrethrum roseum, bearing on half of 

 its disk elongated corolla tubes, and on the 

 other half the small disk-florets of the typical 

 species. 



It is a current belief, that varieties are im- 

 proved by continued culture. I have never been 

 able to ascertain the grounds on which this con- 

 viction rests. It may be referred either to the 

 purity of the race or to the complete develop- 

 ment of the varietal character. In the first case 

 it is a question of hybrid mixtures from which 

 many young varieties must be freed before be- 

 ing placed on the market. But as we have al- 

 ready seen in a former lecture, this requires 

 only three or four years, and afterwards the 

 degree of purit}^ is kept up to the point which 

 proves to be the most suitable for practical 

 purposes. The complete development of the 

 varietal character is a question restricted to 

 ever-sporting varieties, since in white flowers 

 and other constant varieties this degree is va- 

 riable in a very small and unimportant meas- 



