ORIGIN OF SPECIES IN NATURE. 
265 
that they might not disappear even in a good soil. Thus coleus, 
hollies, pelargonia, &c., 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 ‘ 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.” Yerlot 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 CalceolariapiaJUtaginea,) 
Senecio cruentus (garden cineraria), CEnothefa Drummondii , 
Scabiosa atropurpurea, Iberis umbellata, &c. 
Of those sown in spring-time, he mentions Impatiens bdlsa- 
mina, Callisteplms sinensis , Tagetes 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 Rhododendron were obtained by 
using pollen taken from the anthers of the shorter stamens. 
