Chap V. LACTUCA SATIVA. 173 



the unfavourable season of 1867, so that I got few seeds, 

 especially from the self-fertilised heads, which were extremely 

 sterile. The crossed and self-fertilised plants raised from these 

 seeds were measured before they were in fall flower, as in the 

 preceding table. 



The four crossed plants averaged 17*12, and the four self- fer- 

 tilised 15-37 inches in height; or as 100 to 90. One of the self- 

 fertilised plants in Pot III. was killed by an accident, and its 

 fellow pulled up ; so that when they were again measured to the 

 summits of their flowers, there were only three on each side ; 

 the crossed now averaged in height 32-83, and the self-fertilised 

 30-16 inches; or as 100 to 92. 



XX. COMPOSITE. Lactuca sativa. 



Three plants of Lettuce* (Great London Cos var.) grew close 

 together in my garden ; one was covered by a net, and produced 

 self-fertilised seeds, the other two were allowed to be naturally 

 crossed by insects; but the season (1867) was unfavourable, and 

 I did not obtain many seeds. Only one crossed and one self- 

 fertilised plant were raised in Pot I., and their measurements are 

 given in the following table (LXVL). The flowers on this one 

 self-fertilised plant were again self-fertilised under a net, not 

 with pollen from the same floret, but from other florets on the 

 same head. The flowers on the two crossed plants were left to 

 be crossed by insects, but the process was aided by some pollen 

 being occasionally transported by me from plant to plant. These 

 two lots of seeds, after germinating on sand, were planted in 

 pairs on the opposite sides of Pots II. and III., which were at 

 first kept in the greenhouse and then turned out of doors. The 

 plants were measured when in full flower. The following table, 

 therefore, includes plants belonging to two generations. When 

 the seedlings of the two lots were only 5 or 6 inches in height 

 they were equal. In Pot III. one of the self-fertilised plants 

 died before flowering, as has occurred in so many other cases. 



* The Compositas are well- It is very improbable that all the 



adapted for cross-fertilisation, but varieties which were thus culti- 



a nurseryman on whom I can vated near together flowered at 



rely, told me that he had been in different times ; but two which I 



the habit of sowing several kinds selected by hazard and sowed 



of lettuce near together for the near each other did not flower at 



sake of seed, and had never ob- the same time ; and my trial 



served that they became crossed. failed. 



