Increase in Variability in One Direction. 15 
be waited for. This is most forcibly brought out by the 
fact that numerous horticultural varieties are still at 
exactly the same level as they were at the time of their 
introduction. The most vigorous selection continued over 
long periods of time has only rarely succeeded in effecting 
a further improvement in the same direction. We are 
familiar with hosts of variegated plants, but Aurea vari- 
eties are very rare. Flowers with petalomany are sterile, 
and the plants can only be multiplied by vegetative meth- 
ods. But it is quite clear that this difficulty is by no means 
the cause of their rarity. Amongst composites we occa- 
sionally find isolated heads without tongue florets, but 
how small is the number of discoid varieties. I once 
found an example of Coreopsis tinctoria in my cultures, 
which exhibited only some spare ray florets, but although 
I isolated the plant, the abnormality did not reappear 
from its seed. Catacorolla (an outward doubling of the 
corolla so as to form lappets) occurs almost only as a 
commercial race in Gloxinia superba. Fistulous compo- 
sites are rare ; there is room on the market for monoph- 
yllous and laciniate varieties of many species, if only we 
could make them. But so long as chance does not put 
them into our hands, all our labor is in vain. 
Nevertheless, all plants no doubt possess numerous 
latent characters. Any culture carried out on a sufficiently 
large scale, or continued for several years, will give con- 
vincing proof. In fact it is often very difficult to keep 
races free from anomalies. Agrostemnia Githago, Raph- 
anus Rhaphanistnun and many other species contain an 
almost inconceivable number. Amongst garden plants 
desirable novelties must obviously be rare now because 
thev must have been already found and put on the market ; 
