. Genetics in relation to agriculture. Livestock; Heredity; Variation (Biology); Plant breeding. ON VARIETIES IN PLANTS 307 sitions in their day and were doubtless considerably larger than the oldest varieties. The first definite reference to size is found in New Large Purple, listed in 1845. As this occurs in the darkest color group and 15 years before the hj^brid origin of a new variety, Blue Edged, was even suggested, it probably represents a factor mutation. That such mutations actually occurred in the sweet pea is proved by the fact that Countess Spencer and Gladys Unwin were both decided
. Genetics in relation to agriculture. Livestock; Heredity; Variation (Biology); Plant breeding. ON VARIETIES IN PLANTS 307 sitions in their day and were doubtless considerably larger than the oldest varieties. The first definite reference to size is found in New Large Purple, listed in 1845. As this occurs in the darkest color group and 15 years before the hj^brid origin of a new variety, Blue Edged, was even suggested, it probably represents a factor mutation. That such mutations actually occurred in the sweet pea is proved by the fact that Countess Spencer and Gladys Unwin were both decidedly larger than Prima Donna from the very first. The same is true as regards number of flowers in the cluster. Prima Donna, according to Beal's description, bore two or three, usually three, flowers on a stalk, while Countess Spencer has three to four flowers in a cluster. Many of the recent Spencer. Fig. 122.—On the left, Snapdragon sweet peas. On the right, double sweet pea, White Wonder. {From Beat,) varieties bear almost uniform^ four-flowered clusters. The original form and earliest varieties had two flowers in the cluster. The oldest varieties definitely known to bear more than two flowers on a stalk are Invincible Scarlet (18G5) and Crown Princess of Prussia (1868). As these antedate the era of hybridization it is probable that the increased number arose by mutation. Novelty forms have also arisen from time to time. In double sweet peas there are two standards instead of one. In some varieties this character has been fixed by selection so that most of the flowers come double. It gives the effect of increased size (Fig. 122). In the snap- dragon type of flower (Fig. 122) the standard is folded around the wings. It is recessive to erect standard and gives a simple Mendelian ratio of 3 erect to 1 snapdragon in Digitized by Microsoft®. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloratio
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