THE MOVEMENTS AND HABITS OF PLANTS. H 



no loss of purity to the variety ; and this would yield far 

 more favorable results than a mere exchange of seeds. 

 We have seen in my experiments how wonderfully the 

 offspring profited in height, weight, hardiness, and fer- 

 tility, by crosses of this kind. For instance, plants of 

 Ipomcea thus crossed were to the intercrossed plants of 

 the same stock, with which they grew in competition, as 

 100 to 78 in height, and as 100 to 51 in fertility ; and 

 plants of Eschscholtzia similarly compared were as 100 to 

 45 in fertility. In comparison with self-fertilized plants 

 the results are still more striking ; thus cabbages derived 

 from a cross with a fresh stock were to the self-fertilized 

 as 100 to 22 in weight. 



Florists may learn, from the four cases which have 

 been fully described, that they have the power of fixing 

 each fleeting variety of color, if they will fertilize the 

 flowers of the desired kind with their own pollen for 

 half a dozen generations, and grow the seedlings under 

 the same conditions. But a cross with any other in- 

 dividual of the same variety must be carefully prevented, 

 as each has its own peculiar constitution. After a dozen 

 generations of self-fertilization, it is probable that the 

 new variety would remain constant even if grown under 

 somewhat different conditions; and there would no longer 

 be any necessity to guard against intercrosses between 

 the individuals of the same variety. 



MAEEIAGES OF FIEST COUSIN'S. 



With respect to mankind, my son George 

 ■ has endeavored to discover by a statistical in- 

 vestigation whether the marriages of first cousins are at 

 all injurious, although this is a degree of relationship 

 which would not be objected to in our domestic animals ; 

 and he has come to the conclusion from his own re- 



