OCR Text |
Show 182 NEMOPHILA INSIGNIS. CHAP. v. in tho s~nne pot were again self-fertilised with pollen from the ~tnt hers of other flowers on the same plant. Therefore the degree of self-fertilisation was not quite so . close as in tho last generation, in which pollen from the same flower, kept in paper, was used. These two lots of seeds were thinly sown on opposite sides of nine pots; and the young seedlings were thinned, an equal number of nearly as possible tho same ago being loft on tho two sides. In the spring of the following year (1870), when the seedlings had grown to a considerable size, they wore n1easured to the tips of their leaves; and tho twenty-throe crossed plants averaged 14 · 04 inches in hojght, whilst the twentythree self-fertilised seedlings were 13 ·54 inches; or as 100 to 96. In the summer of the same year several .of those plants flowered, the crossed and self-fertilised plants flowering almost simultaneously, and all the flower-stems were measured. Those produced by eleven of tho crossed plants averaaod 30 · 71 inches, and those by nine of the self-fertilised plants 29·43 inches in height; or as 100 to 96. Tho plants in these nino pots, after they had flowered, were ropotted without being disturbed in much larger pots; and in tho following year, 1871, all flowered freely; but they had grown into such an entangled mass, that the separate plants on each side could no longer be distinguished. Accordingly three or four of the tallest flower-stems on each side of each pot were measured; and the measurements in tho preceding table are, I think, more trustworthy than tho previous ones, from being more numerous, and from the plants being well established and growing vigorously. Tho average height of the thirty-four tallest flower-stems on the twenty-three crossed plants is 29 · 82 inches, and that of tho same number of flower-stems on the same number of selffertilised plants is 27 ·10 inches; or as 100 to 91. So that the crossed plants now showed a decided advantage over their selffertilised opponents. XXII. POLEMONIACElE.-NEMOPHILA INSIGNiS. Twelve flowers were crossed with pollen from a distinct plant, but produced only six capsules, containing on an average 18 · 3 seeds. Eighteen flowers were fertilised with their own pollen and produced ten capsules, containing on an average 12·7 CHAP. v. NEMOPHILA INSIGNIS. 183 seeds; so that the seeds per capsule were as 100 to 69.* The crossed seeds weighed a little less than an equal number of selffertilised seeds, in the proportion of 100 to 105; but this was clearly due to some of the self-fertilised capsules containing very few seeds, and these were much bulkier than the others, from having been better nourished. A subsequent comparison of the number of seeds in a few capsules did not show so great a superiority on the side of the cros13ed capsules as in the present case. The seeds were placed on sand, and after germinating were planted in pairs on the opposite sides of five pots, which were kept in the greenhouse. When the seedlings were from 2 to 3 inches in height, most of the crossed had a slight advantage over the self-fertilised. The plants were trained up sticks, and thus grew to a considerable height. In four out of the five pots a crossed plant flowered before any one of the self-fertilised. TABLE LXXII. Nemophila insignis; 0 means that the plant died. No. of Pot. Crossed Plants. Self-fertilised Plants. Inches. Inches. I. 32~ 2q II. 34~ 23§ III. 33~ 19 22i 72 "!!" 29 17~ -- IV. 35~ 10~ 33~ 27 V. 35 0 38 18~ 36 20~ Wl~ 34 32~ 0 Total in inches. 399 •38 199·00 . * Several species of Polemomacere are known to be proterandrous, but I did not attend to this point in Nemophila. Verlot says(' Des Varietes,' 18G5, p. 66) that varieties growing near one another spontaneously intercross. |