FLOWERS. 129 



162. And, on the other hand, whatever tends to produce excessive 

 vigour, causes the dispersion of sap, or prevents its elaboration, and causes 

 sterility. 



163. Transplantation with a partial destruction of roots, age, or high 

 temperature accompanied by a dry atmosphere, training obliquely or in 

 an inverted direction, a constant destruction of the extremities of young 

 growing branches, will all cause an accumulation of sap, and secretions ; 

 and, consequently, all such circumstances are favourable to the production 

 of flower-buds. 



164. But a richly manured soil, high temperature, with great atmospheric 

 humidity, or an uninterrupted flow of sap, are all causes of excessive vig- 

 our, and are consequently unfavourable to the production of flower-buds. 



165. There is a tendency in many flowers to enlarge, to alter their 

 colours, or to change their appearance by transformation and multiplication 

 of their parts, whenever they have been raised from seed for several gene- 

 rations, or domesticated. 



166. The causes of this tendency are probably various, but being entirely 

 unknown, no certain rules for the production of varieties in flowers can be 

 laid down, except by the aid of hybridizing (201). 



167. It often happens that a single branch produces flowers different 

 from those produced on other branches. This is technically called a sport. 



16S. As every bud on that branch has the same specific vital principle 

 (113), a bud taken from such a branch will produce an individual, the 

 whole of whose branches will retain the character of the sport. 



169. Consequently, by buds an accidental variety may be made perma- 

 nent, if the plant that sports be of a firm woody nature (98). 



170. As flowers feed upon the prepared sap in their vicinity, the greater 

 the abundance of this prepared food, the more perfect will be their devel- 

 opement. 



171. Or the fewer the flowers on a given branch, the more food they will 

 severally have to nourish them, and the more perfect will they be. 



172. The beauty of flowers will therefore be increased either by an abun- 

 dant supply of food, or by a diminution of their numbers (thinning), or by 

 both. The business of the pruner is to cause these by his operation. 



173. The beauty of flowers depends upon their free exposure to light 

 and air, because it consists in the richness of their colours, and their colours 

 are only formed by the action of these two agents (281). 



174. Hence flowers produced in dark or shaded confined situations are 

 either imperfect, or destitute of their habitual size and beauty. 



175. Double flowers are those in which the stamens are transformed 

 into petals ; or in which the latter, or the sepals, are multiplied. They 

 should not be confounded with Proliferous (183), and Discoid Compound 

 Flowers (184). 



176. Although no certain rules for the production of double flowers can 

 be laid down, yet it is probable that those flowers have the greatest tendency 

 to become double, in which the sexes are habitually multiplied. 



177. In Icosandrous and Polyandrous plants either the stamens or the 

 pistilla are always very numerous when the flowers are in a natural state ; 

 and it is chiefly in such plants that double flowers occur, when they become 

 transformed 



