OP DIMORPHIC A^'D TRIMORPUIC PLANTS. 421 



in the seedlings always occupied their proper position low down in 

 the corolla ; and the pollen-grains were of the small size proper to 

 the long-styled form, but were mingled with many minute and shri- 

 velled grains. The yellow-flowered and the purple-flowered plants 

 of this first generation were fertilized under a net by their own 

 pollen, and the seed separately sown. From the former, 22 plants 

 w^ere raised, and all were yellow^ and long-styled. From the latter 

 or the purple-flowered plants, 21 long-staled plants were raised, of 

 which 17 were purple and 7 yellow. In this last case we have an 

 instance of reversion in colour, without the possibility of any 

 cross, to a great-grandparent or to a more distant ancestor if the 

 parent of the Edinburgh plant was not yellow. Altogether, 23 

 plants in the first generation, and 46 in the second generation, 

 were raised j and the whole of these 69 illegitimate plants were 



long-styled. 



Eight purple-flowered and two yellow-flowered plants of the 

 first illegitimate generation were fertilized in various ways by 

 their own pollen and by that of the common Primrose ; and the 

 seeds were separately counted, but I could detect no difference 

 in the fertility of the purple and yellow varieties. Hence, in the 

 Table on the following page, the results are run together. 



If we compare the figures in this Table with those previously 

 given, showing the normal fertility of the common Primrose, we 

 shall see that the illegitimate purple- and yellow-flowered varieties 

 are very sterile. For instance, 72 flowers were fertilized with 

 pollen from the same plants and produced only 11 good capsules ; 

 but by the standard they ought to have produced 48 capsules ; 

 and each of these ought to have contained on an average 52*2 seeds, 

 instead of only 11-5 seeds. When these plants were illegiti- 

 mately and legitimately fertilized by pollen from the common 



Primrose, the average numbers were increased, but were far from 

 attaining the normal standards. So it was when both forms of the 

 common Primrose were fertilized by pollen from the illegitimate 

 varieties ; and this shows that their male as well as their female 

 organs are in a deteriorated condition. The sterility of these 

 plants was shown in another way, namely, by their not producing 

 any capsules when the access of all insects (except such minute 

 ones as Thrips) was prevented ; for under these circumstances the 

 common long-styled Primrose produces a considerable number of 

 capsules. Hence there can be no doubt that the fertility of these 

 plants is greatly impaired. The loss is not correlated with the 

 colour of the flower ; and it w^as to ascertain this point that I made 



