0BSE11VATI0NS UPON MULING AMONG PLANTS. 17 1 



affinity between nearly allied species : the degree, however, of such 

 affinity is not confined merely to the more speedy occurrence of 

 the signs of fecundation, but extends to the whole process of 

 fructification up to the maturation of the seeds. For instance, 

 the union of Aquilegia atropurpurea 5 with Canadensis vul- 

 garis and glandulosa, as of Dianthus barbatus $ with 

 superbus, Japonicus, Armeria, Chinensis, &c, produces fruit 

 and seeds of very different degrees of perfection and number, 

 which in point of fact are the very product which reveals 

 especially the true degree of elective affinity amongst plants. In 

 some cases, as in Nicotiana macrophylla and suaveolens with 

 N. paniculata, union takes place very readily, and up to a 

 certain point everything seems to tend to perfection ; but then a 

 yellow ring is formed at the point where the capsule is fixed, and 

 the seeds make no further progress. The pollen of one species 

 may be capable of fructifying several, as that of D. superbus 

 fructifies barbatus, Armeria, Chinensis, caryophyllus , Cau- 

 casicus, arenarius ; but it will not impregnate them in the same 

 degree, but with greater perfection in the order in which the 

 species are written down. The variation in the number of seeds 

 is very great. Supposing the number of seeds in pure species of 

 Dianthus to vary from eighty to one hundred and twenty, that 

 in hybrids will vary as much as from two to fifty-four. 



There is, however, another point of view in which this affinity 

 must be considered. When two species, of which the first 

 furnishes the matrix, the second the pollen, unite for the pro- 

 duction of hybrid fecundation, judging from the reciprocity so 

 general in the admixture of varieties, we might look for reci- 

 procity of elective affinity, and expect as much success when 

 the second affords the matrix and the first the pollen. Though 

 this takes place in typical hybrids and in the crossing of varieties, 

 the case is very different with pure species. The degree of 

 elective affinity, therefore, is quite altered, and sometimes reduced 

 to nothing, the species remaining the same, the sexes and the 

 proportion of their energy being changed. Sexual affinity 

 does not observe systematic or morphological laws. One of 

 the most striking examples is that of Nicotiana Langsdorjii, 

 which fructifies in a decreasing ratio N. paniculata, vinccefiora, 

 suaveolens, glauca, and rustica, though not susceptible of im- 

 pregnation from these species, or Chinensis, macrophylla, quadri- 

 valvis, and glutinosa. It is to be observed that in all those 

 cases in which entire absence of elective affinity exists on the one 

 side, the produce on the other is mostly very small, or fails in 

 the majority of numerous experiments. 



The want of perfect reciprocity of sexual force even in the 

 most nearly allied species of the same genus shows that the male 



