CHAP. I. INTRODUCTORY REMARKS. 25 



placed on one side of the large stigma in sixty-four 

 flowers of Ipomoea purpurea, and a great mass of pollen 

 over the whole surface of the stigma in sixty-four other 

 flowers. In order to vary the experiment, half the 

 flowers of both lots were on plants produced from self- 

 fertilised seeds, and the other half on plants from 

 crossed seeds. The sixty -four flowers with an excess 

 of pollen yielded sixty-one capsules; and excluding 

 four capsules, each of which contained only a single 

 poor seed, the remainder contained on an average 5 07 

 seeds per capsule. The sixty-four flowers with only a 

 little pollen placed on one side of the stigma yielded 

 sixty-three capsules, and excluding one from the same 

 cause as before, the remainder contained on an average 

 5 '129 seeds. So that the flowers fertilised with little 

 pollen yielded rather more capsules and seeds than did 

 those fertilised with an excess ; but the difference is 

 too slight to be of any significance. On the other 

 hand, the seeds produced by the flowers with an excess 

 of pollen were a little heavier of the two ; for 170 of 

 them weighed 79 67 grains, whilst 170 seeds from the 

 flowers with very little pollen weighed 79-20 grains. 

 Both lots of seeds having been placed on damp sand 

 presented no difference in their rate of germination. 

 We may therefore conclude that my experiments were 

 not affected by any slight difference in the amount of 

 pollen used ; a sufficiency having been employed in 

 all cases. 



The order in which our subject will be treated in 

 the present volume is as follows. A long series of ex- 

 periments will first be given in Chapters II. to VI. 

 Tables will afterwards be appended, showing in a con- 

 densed form the relative heights, weights, and fertility 

 of the offspring of the various crossed and self-fertilised 



