01UGIN OF SPECIES IN NATURE. 



265 



that they might not disappear even in a good soil. Thus coleus, 

 hollies, pelargonia, &o., appear now to be pretty well fixed in the 

 various colorations of their foliage. 



Dwarfing. — There are many more dwarf annuals than peren- 

 nials in cultivation. This is only because the latter are not 

 usually raised from seed. 



On the appearance of a dwarf, it is necessary to isolate it ; 

 so that it be not crossed with taller ones. Then one must keep 

 selecting seed from the shortest of the seedlings, till the 

 " nanism " be fixed. This fixing varies from one to six years ; 

 but it is not known why there should be this variation in time. 



The methods of producing dwarfs are possibly several. The 

 following have been suggested. Bearing in mind that the object 

 is to " arrest vegetative growth," anything that will do this may 

 produce dwarfing, not only in an individual, but in its progeny. 



By autumn sowing (Aug.-Sept.) : When it is too late for a 

 plant to flower, it produces a more compact vegetation. If it 

 be sown in spring, successive prickings out and transplanting, 

 so that each plant grows freely, will result in strong thick-set 

 plants. " This process will favour the development of the lower 

 ramifications at the expense of the main stem ; we thus create 

 an individual, comparatively dwarf. If now we collect seed from 

 plants thus grown, and if we give the same treatment to them 

 as to their parents, we shall obtain year after year 4 plants 

 which we shall have made to develop a certain tendency to 

 nanism.' That is, after some years, they will be more apt to pro- 

 duce dwarf varieties." Verlot adds that the greater number of 

 cultivated dwarfs were of varieties sown in autumn ; or if in spring, 

 they have been subjected to successive transplanting. Of the 

 first he mentions eleven varieties, such as Calceolaria piantaginedj 

 Senecio cruentus (garden cineraria), CEnothera JDrummondii, 

 Scabiosa atropurpurea, Iberis umbellata, &c. 



Of those sown in spring-time, he mentions Impatiens balsa- 

 mina, Callistcphus sinensis, Tagctes patula, T. erecta, and 

 T. signata. 



With regard to the procuring of dwarfs by fecundation of 

 flowers, ordinary crossing has usually an opposite tendency in 

 making the offspring more vigorous ; but Mr. McNab found 

 that the best dwarf varieties of Bhododendron were obtained by 

 using pollen taken from the anthers of the shorter stamens. 



