2/0 Non-Isolable Races. 

multiformity and instability corroborate this view. It 
is only the commonness of variegated sorts and the great 
interest which attaches to them which brings them to be 
regarded as analogous to the best constant varieties. 
o o 
Moreover this view is supported by the general opinion 
that a complete development of the yellow color would 
characterise the supposed constant variety, but that it 
would at the same time of necessity lead to the destruc- 
tion of the plants. In this conception variegation is re- 
garded as an incomplete anomaly whose complete con- 
dition would involve its own destruction ; but this view 
is incorrect. 1 Complete yellow varieties are not only pos- 
sible and capable of existence but actually well known in 
horticulture, although the number of such forms is small. 
Instances can be found in seedsmen's catalogues; e. g., 
Sainbucus uiyra aurca and Fra.vinus c.rcclsior aurea, also 
the aurca varieties of Chrysanthemum carinatum, Mira- 
bilis Jala pa, Scabiosa atropurpurca, Hiunulus japomcus 
(liitcsccns) etc. These plants, so far as I know, are all 
either yellowish-green or golden-yellow. 2 They also ap- 
pear to be very constant and never or very seldom to 
revert to the green type. I have made a number of ex- 
perimental sowings on a large scale of the seeds of the 
ordinary golden-yellow variety of Chrysanthemum Par- 
/ <j / . 
thenium? (Matncaria c.viiiria nana coinpacta foliis aurcls 
Hoj't.) and did not find amongst the many hundred ex- 
amples a single atavist ; neither green nor variegated seed- 
lings occurred. But amongst other commercial seeds I 
o o 
have not found so great a degree of purity, the admixture 
1 See 3 of this part (pp. 18-26). 
2 T have not grown all the above forms myself; and it should be 
noticed that the name an r ens does not always relate to uniformly 
colored sorts, e. g., Agave striaia aurca. 
3 ViLMORiN, B lumen gartnereij Vol. IT, p. 509. 
