Island. Crossed with the much less hard} - orange, desirable 
varieties of fruit called citranges, hardy much further north than 
the orange, have been produced. 
Varieties of plants and animals are very likely to develop new 
traits and new characters when exposed to new sets of conditions. 
Thus the kea parrot of New Zealand changed from a herbivor- 
ous to a carnivorous bird some years after the introduction of 
sheep and hence became a great pest. Marked changes of color 
in certain species of birds are said to be brought about by 
changes in the substances on which they feed. The tall trees of 
one country may be the dwarfs of another. The Mexican Par- 
thenium or guayule rubber plant failed to produce as much 
rubber when taken away from its desert environment and culti- 
vated. The obscure and little known insects and wild plants of 
one part of the world may be the scourges of another, as for ex- 
ample the Chinese San Jose scale in America, the American 
cactus in Australia, the Russian thistle in western America. 
But on the other hand, after all that has been said concerning 
variability, it is still a fact that certain living organisms are so 
strikingly similar as regards certain characters, that we are able 
to group them roughly into varieties, species, genera, and fam- 
ilies. Certain characters appear to be less variable than others, 
both inherently and when subjected to differences in environment 
and these are known as fundamental characters and are often 
made the basis for the groupings mentioned above. This group- 
ing or classification, however, is in many respects artificial and 
must always remain more or less so— serving largely as a con- 
venient method of keeping track of them— of pigeon-holing them, 
so to speak, so that we may talk about them. A striking illustra- 
tion of the stability of certain characters is that exhibited by 
plants propagated by bulbs such as tulips and hyacinths. We 
are told, on the authority of Darwin, that a certain Dutch bulb- 
grower was repeatedly able to identify 1200 varieties of hyacinths 
by observations on the bulbs alone. 
There are said to be over 200,000 reliable species of plants, 
and for the most part there is very little difficulty in identifying 
them by certain character descriptions. But sometimes these 
species are not so sharply differentiated as the descriptions in 
the manuals would lead one to infer, and specimens that one 
specialist might consider as species A, would be classified by an 
equally eminent authority as species B. The story is told of a 
certain eminent botanist to whom was sent a plant for identifica- 
tion, that he identified it as species A the first year and on 
receiving specimens from the same plant the second year, he 
classified it as species B, remarking in self-defense when the cir- 
cumstances were explained to him, that his conception of species 
A had changed in the interim. 
