84 Sudden Appearance and Constancy. 
Catananche cocntlca alba (5), Hyssopus officinalis albus 
(198), Lobelia syphilitica alba (537), Lychnis chalcedo- 
nica alba (401), Polemonium dissectum album (126), 
Sak'ia sylvestris alba (296). The following white vari- 
eties of annual species I also found to be perfectly con- 
stant : Chrysanthemum coronariiim album (400), Godetia 
amocna, white Pearl (15), Linum usitatissimum album 
(779), Phlox Drummondi alba (50), Silene Armeriaalba 
(617). Among wild species I subjected especially Ero- 
dium ciciitarium album, which is common in Holland, 
to a severe test. In this form the pigment characteristic 
of the species is lacking both in the leaves and in the 
flowers. I found the variety constant through five gen- 
erations in my experimental garden, not a single red 
plant appearing although the sowings were conducted on 
a very large scale. Later I collected seeds of the "car. 
alba from another locality and found it also to be con- 
stant (43 specimens). 
Other color varieties usually prove equally pure if 
the seeds of plants that have been isolated are sown. In 
some cases this fact is so generally known that they have, 
on this ground, been raised to the rank of species, as, 
for instance, Anagallis (arvensis} coendca. In 1897 I 
had 25 examples of this variety flowering on an isolated 
spot, and from these in 1898 I had 866 plants which were 
without exception blue. Tetragonla e.rpansa, whose leaves 
and flowers are normally reddish brown, has given rise 
to a pure green form which has been raised to the rank 
of a species under the name of T. crystalline,. This I 
also found perfectly constant. In 1898 I sowed about 
600 fruits obtained from a culture of 1897. Each fruit 
contains from 6 to 10 and often more seeds, which ger- 
minate sooner or later, some of them not until after a 
