CEREALS AND FRUIT-TREES 151 
varieties alone having been preserved by the care of 
man. The Wheats are a case in point. While a wild 
grass growing in Palestine has been quite recently 
identified as the probable source of the Hard Wheats, 
the native parent of the Soft Wheats is unknown. 
That productiveness has in all cases been much 
increased by long selection there can be no doubt; it 
may be pointed out that several species of Triticum, 
Hordeum, and Avena, allies of the Wheat, Barley, and 
Oat, are included in the native British flora, but they 
are useless as producers of grain. 
Nowhere is the effect on plants of selection and 
cultivation seen better than in our native fruit-trees. 
We have only fo compare the size, flavour, and almost 
endless variety of apples and pears with the fruit of 
the wild stock of these two species—the Crab (Pyrus 
Malus) and Wild Pear (Pyrus communis) of our 
hedgerows—to realize how much has been accom- 
plished. In garden flowers, also, we see most striking 
results of continuous selection. By taking advantage 
of the tendency of stamens and carpels to change 
occasionally into petals, and of petals to increase in 
number, “double flowers” have been effected. When 
“doubling” is complete—that is, when the conversion 
into petals is thorough—no seed can of course be 
produced, and the plants must be propagated by 
cuttings. Different other slight natural variations, 
exaggerated by selection and cultivation, have been 
the source of innumerable “ varieties ” in our gardens. 
Sometimes the natural variation is by no means 
slight, but of a striking character which the efforts of 
gardeners have not succeeded in developing further. 
Take, for instance, the case of fastigiate trees, such as 
