CHAP. V. HETEROSTYLED TRIMORPHIC PLANTS. 205 



of corresponding height from both the other forms. 

 But the case last given shows that the application of 

 two kinds of pollen is not indispensable for the pro- 

 duction of all three forms. Hildebrand has suggested 

 that the cause of all three forms being regularly and 

 naturally reproduced, may be that some of the flowers 

 are fertilised with one kind of pollen, and others on 

 the same plant with the other kind of pollen. Finally, 

 of the three forms, the long-styled evinces somewhat 

 the strongest tendency to reappear amongst the off- 

 spring, whether both, or one, or neither of the parents 

 are long-styled. 



The lessened fertility of most of these illegitimate 

 plants is in many respects a highly remarkable phe- 

 nomenon. Thirty-three plants in the seven classes 

 were subjected to various trials, and the seeds care- 

 fully counted. Some of them were artificially fertil- 

 ised, but the far greater number were freely fertilised 

 (and this is the better and natural plan), through the 

 agency of insects, by other illegitimate plants. In the 

 right hand, or percentage column, in the following 

 table, a wide difference in fertility between the plants 

 in the first four and the last three classes may be per- 

 ceived. In the first four classes the plants are de- 

 scended from the three forms illegitimately fertilised 

 with pollen taken from the same form, but only 

 rarely from the same plant. It is necessary to observe 

 this latter circumstance; for, as I have elsewhere 

 shown,* most plants, when fertilised with their own 

 pollen, or that from the same plant, are in some 

 degree sterile, and the seedlings raised from such 

 unions are likewise in some degree sterile, dwarfed, 

 and feeble. None of the nineteen illegitimate plants 



* ' The Effects of Cross and Self-fertilisation in the Vegetable King- 

 dom,' 1876. 



