Chap. Vn. TABLE A. 275 



with plants raised by a cross with a fresh stock, the crossed 

 greatly exceeded the self-fertilised in height, weight, and fertility 

 (when these two latter points were attended to), the present case 

 must be looked at as an anomaly not affecting the general rule. 

 The most probable explanation is that the plants grew pre- 

 maturely, owing to the seeds of the last generation not having 

 been well ripened; for I havo observed an analogous case with 

 Ibcris. Self-fertilised seedlings of this latter plant, which wero 

 known to have been produced from seeds not well matured, 

 grew from the first much more quickly than the crossed plants, 

 which were raised from better matured seeds ; so that having 

 thus once got a great start they were enabled ever afterwards to 

 retain their advantage. Some of these same seeds of the Ibcris 

 were sown on the opposite sides of pots filled with burnt earth 

 and pure sand, not containing any organic matter ; and now the 

 young crossed seedlings grew during their short life to double 

 the height of the self-fertilised, in the same manner as occurred 

 with the above two sets of seedlings of Petunia which were much 

 crowded and thus exposed to very unfavourable conditions. We 

 have seen also in the eighth generation of Ipomcea that self- 

 fertilised seedlings raised from unhealthy parents grew at first very 

 much more quickly than the crossed seedlings, so that they wero 

 for a long time much taller, though ultimately beaten by them. 



(4, 5, 6.) EscltsclioUzia californica. Four sets of measure- 

 ments are given in Table A. In one of these the crossed plants 

 exceed the self-fertilised in average height, so that this is not 

 one of the exceptions here to be considered. In two other 

 cases the crossed equalled the self-fertilised in height within five 

 per cent.; and in the fourth case the self-fertilised exceeded the 

 crossed by above this limit. We have seen in Table C that the 

 whole advantage of a cross by a fresh stock is confined to the 

 number of seeds produced, and so it was with the disadvantage 

 from self-fertilisation with the intercrossed plants of the same 

 stock compared with the self-fertilised, for the former were in 

 fertility to the latter as 100 to 89. The intercrossed plants thus 

 have at least one important advantage over the self-fertilised. 

 Moreover, the flowers on the parent-plants when fertilised with 

 pollen from another individual of the same stock yield far moro 

 seeds than when self-fertilised ; the flowers in this latter case 

 being often quite sterile. We may therefore conclude that a 

 cross does some good, though it does not give to the crossed 

 seedlings increased powers of growth. 



T 2 



