352 THE SELF-FERTILIZATION OF PLANTS. 



open ground; to carefully exclude insects; and then 

 to fertilize some of the flowers with pollen from the 

 same flower, and others on the same plant with pollen 

 from a distinct, but adjoining plant. In many, but not 

 all, of these experiments, the crossed plants yielded 

 much more seed than the self-fertilized plants; and I 

 have never seen the reversed case. * * * Now, I 

 have carefully observed the growth of plants raised 

 from crossed and self-fertilized seed, from their germi- 

 nation to maturity, in species of the following genera, 

 namely, Brassica, Lathyrus, Lupinus, Lobelia, Lac- 

 tuca, ' Dianthus, Myosptis, Petunia, Linaria, Calceo- 

 laria, Miranda, and Ipomcea, and the difference in 

 their powers of growth and of withstanding, in cer- 

 tain cases, unfavorable conditions, was most manifest 

 and strongly marked." ***** 



" I will briefly describe the two most striking cases as 

 yet observed by me. Six crossed, and six self-fertil- 

 ized seeds of Ipomoea purpurea from plants treated in 

 the manner above described, were planted as soon as 

 they had germinated, in pairs, on opposite sides of 

 two pots, and rods of equal thickness were given them 

 to twine up. Five of the crossed plants grew from the 

 first more quickly than the opposite self-fertilized 

 plants ; the sixth, however, was weakly, and was for a 

 time beaten, but at last its sounder constitution pre- 

 vailed, and it shot ahead of its antagonist. As soon as 

 each crossed plant reached the top of its seven foot 

 rod, its fellow was measured, and the result was that 

 when the crossed plants were seven feet high, the self- 

 fertilized had attained the average height of only five 

 feet, four and a half inches. The crossed plants 

 flowered a little before, and more profusely than the 

 self- fertilized plants. On opposite sides of another 

 small pot, a large number of crossed and self-fertilized 

 seeds were sown, so that they had to struggle for bare 

 existence; a single rod was given to each lot: here 



