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 hybrid 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 Seal'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 



FIQ. 122. On the left, Snapdragon sweet peas. On the right, double sweet pea, White 



Wonder. (From Seal.) 



varieties bear almost uniformly 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 (1865) 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 F t . 



