Double Flowers and Flowerheads. 
199 
and other bulbous plants. 1 There is a certain periodicity 
in this case too ; for sometimes the first, but more usually 
the later, flowers are less double than those which bloom 
in the height of the flowering period. This fact is well 
known to breeders,- especially in the case of certain 
double varieties of Begonia in which seeds can only be 
saved from the autumn flowers. 
Fig. 36. Pyrethrum roscuin, from the nursery of Messrs. 
KRELAGE & SON in Haarlem (1899). In one half (the 
rear half in A, the left in B) the inflorescence is made 
"double" by the elongation of the tube-florets ; in the 
other half it is "single." A, oblique view; B, section. 
The majority of double varieties are constant from 
seed, even in the case of trees and shrubs (varieties of 
the peach and the apple for instance), 3 others appear to 
be only slightly so, and others not at all (Pmnns spi- 
1 LiNDLE\^ Theory of Horticulture, p. 333. 
2 CARRIERE, Production ct fixation dcs varietcs, 1865, pp. 66 and 
67 (Camellia alba plena, incarnata, Fuchsia, etc.). 
S VERLOT, loc. cit., p. 83. 
