100 JOUKNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



greater in rather exhausted soil, as can easily be proved by allowing a bed 

 to sow itself from the previous year's bloom, and the plants to flower on 

 the same ground without manuring, &c." As another illustration, the 

 second and weaker growth of Peas, issuing from the lower part of the 

 stem, bore double flowers. Hence an enfeebled constitution also appears 

 in this case to have been the cause. Similarly, weak plants of Lapageria 

 bore doable flowers, while stronger plants grown with them bore only 

 single flowers. 



Frost affecting early shoots of Roses and early-blossoming Pelargo- 

 niums, as well as the reduced temperature of autumn, causes flowers of 

 Apples and Pears to be more or less liable to doubling. 



A check received by repotting Pelargoniums and weakly Cinerarias 

 was noted to produce double flowers. Even too cold water, grubs of 

 insects and minute fungi attacking flowers, thereby checking their 

 development, have been credited with the same result. 



Crossing and hybridising are said to encourage the appearance of 

 double flowers. This is attributed to a slight want of harmony between 

 the sexual organs of the parents, the consequence being deformed seeds. 

 Such occurring in Leucojum, without any crossing, produced plants with 

 double flowers. The well-nourished seeds of Leucojum developed only 

 single flowers. 



Stocks bearing defective sexual organs, due to drought, bore seeds 

 which developed into double-flowering plants. Similarly, Camellia seeds 

 raised in dry conditions gave the same result. 



Hence it will appear that Darwin's acute surmise in 1843 is fully 

 borne out by subsequent experiences. Doubling having been acquired, it 

 may become congenital. Thus Lemoine crossed a semi-double Lilac 

 with pollen from a single, and thirty out of forty seedlings were double or 

 semi-double. Similarly, a hybrid between East Indian Rhododendrons 

 showed a slightly petaloid anther. Mr. Heal pollinated it with its own 

 pollen. The whole of the Balsam;t>floral section is the result of that single 

 impregnation. 



As any influence which may affect the reproductive organs may cause 

 them to attempt a metamorphosis, it is nut surprising to find exactly the 

 reverse conditions to drought may induce doubling where plants have 

 been long habituated to conditions of dryness. Thus Kerria japonica 

 has become double in Europe, including England, but is single in Japan. 

 I have seen the single -flowered form in Sir T. Hanbury's garden at 

 La Mortola, Italy, and in Tunbridge Wells (on sandstone). 



Cardamine pratensis has been found to produce double flowers at two 

 very wet places. 



Reversions from doubles to singles occur when the conditions are 

 changed. Thus double Daffodils become single in poor, cold and wet, or 

 shaded soils. 



Double Balsams when " starved " became single-flowered; but with 

 a liberal treatment bore double flowers, &c. This shows that when 

 " doubling" has been acquired it becomes constitutional, and is greatly 

 improved by high nourishment. But this latter alone does not seem to 

 be capable of bringing about the metamorphosis at first. 



