CHAP. V. HETEROSTYLED DIMORPHIC PLANTS. 233 



tilised with their own pollen, produced 15 capsules, 

 containing an average of 16 3 seeds. As already 

 stated, the probable average with legitimate plants 

 for a union of this nature is rather above 20 seeds. 

 These plants were remarkably healthy and vigorous, 

 as long as they were kept under highly favourable 

 conditions in pots in the greenhouse ; and such treat- 

 ment greatly increases' the fertility of the cowslip. 

 When these same plants were planted during the next 

 year (which, however, was an unfavourable one), out 

 of doors in good soil, 20 self-fertilised flowers pro- 

 duced only 5 capsules, containing extremely few and 

 wretched seeds. 



Four long-styled great-grandchildren were raised 

 from the self-fertilised grandchildren, and were kept 

 under the same highly favourable conditions in the 

 greenhouse ; 10 .of their flowers were fertilised with 

 own-form pollen and yielded the large proportion of 6 

 capsules, containing on an average 18 7 seeds. From 

 these seeds 20 long-styled great-great-grandchildren 

 were raised, which were likewise kept in the greenhouse. 

 Thirty of their flowers were fertilised with their own 

 pollen and yielded 17 capsules, containing on an aver- 

 age no less than 32, mostly .fine seeds. It appears, 

 therefore, that the fertility of these plants of the fourth 

 illegitimate generation, as long as they were kept 

 under highly favourable conditions, had not decreased, 

 but had rather increased. The result, however, was 

 widely different when they were planted out of doors 

 in good soil, where other cowslips grew vigorously and 

 were completely fertile ; for these illegitimate plants 

 now became much dwarfed in stature and extremely 

 sterile, notwithstanding that they were exposed to the 

 visits of insects, and must have been legitimately fer- 

 tilised by the surrounding legitimate plants. A win >lo 



